Phospholipids are amazing molecules. Place them in a watery environment and they self associate into a spherical ball and make membranes. Membranes made of phospholipids are fluid structures which are sticky to themselves, so that they make a barrier which typically defines, in part, the outer boundary of a cell and helps hold things in the cell, yet it remains a fluid. Life would not work without these fluid barriers. Who would of thought of that? What a perfect idea for a membrane, a fluid barrier! We would be very stiff creations indeed if our membranes were not made out of these soapy molecules.
So we see in membranes the same principle we discussed regarding the idea that all macro-organisms are made of smaller pieces or entities we call cells, i.e., membranes are made of lots of smaller parts (phospholipids). Relatedly, we also see modularity, i.e., the parts are somewhat interchangeable and pliable. And this modularity and pliability allows for a lot of things to be stuck in membranes.
But, if phospholipids are sticky (self associate because of hydrophobicity) why don't all cells near one another, stick together and form one big clump....for instance when we bump into each other why don't we form one big glumpy smear of phospholipid humanity on the earth. How do pond organisms swim around with these sticky membranes and not get stuck or fuse together?
In fact this is the secret involved in how some viruses work, they invade cells by fusing their outer lipid membrane envelope with the cell membrane, and they take advantage of this sticky/hydrophobic effect. Works like a charm; the virus fuses to the membrane and releases its contents ( at least some viruses work this way, not all do).
Membranes play important roles in prokaryotic cells also. One prokaryote, the microbial cockatrice has unusual membranes. A cockatrice was a wild dish served at medieval banquets. It was a cooked dish of a rooster fused to a suckling pig. Archaebacteria, as suggested by some microbiologists, are a microbial version of the cockatrice, since they appear to have genomes composed of both prokaryotes and eukaryotes.
However, what is even more interesting is the different kinds of lipids and structures which make up the outer membrane and walls of the archaebacteria. Some archaebacteria have monolayers rather than bilayers in their membranes. They also have different lipids suggesting that the biochemistry involved in making archaebacteria lipids is very different from both eukaryotes and prokaryotes. Their cell wall also contains something called an S-layer which is an intriguing structure. Even more fascinating the flagellum they display is constructed differently from the flagellum of eubacteria.
Questions to answer:
1 Why and how do phospholipids self associate?
2 What prevents membranes from fusing with all other nearby membranes?
3 Could the self assembly of phospholipids be a possible explanation for how the first cell membranes evolved?
4 When phospholipids form membranes in a water based environment, do they make membranes similar to the cell membranes we find in cells today?
5 Explore the structure of the archaebacterial monolayers. How does this contribute to life in the extreme?
6 What is an S-layer and how does it contribute to cell function?
7 We discussed the problems inherent in trying to assemble a flagellum from pieces secreted from the eubacterial cell. How is this problem solved in the archaebacterial flagellum? Or is it solved?
1. Because the phospholipids are amphipathic and polarized two regions: hydrophilic and hydrophobic. When into a aqueous solution, like the cytoplasm, the unification of those phospholipids help them to be stable, since part of them are hydrophobic. Associating in to aggregates (micelles), give each molecule more stability, since the specific areas (hydrophobic and hydrophilic) are associated.
ReplyDelete2. For membranes to fuse in a cell, they depend on energy and protein mediators or “adaptor” molecules. In this way, the fusion between membranes of organelles in a cell can be controlled.
3. As a Christian I don’t believe that would explain first cell creation, even why God created organisms as kinds, and not first a cell that over million years evolved to numerous kinds of organisms. Even for an atheist that would be a hard thing to believe, since it would be necessary a great amount of phospholipids and the presence of some organelles do be involved by the “membrane.”
4. Yes, they are both bilayer, with the lipid part in the center and the hydrophilic part of the molecule in the outsides.
5. The ether bonds found in Archeabacteria phospholipids are more resistant the ester bonds found in the other organism phospholipids; it has branched chains that help the membrane to resist high temperature; the lipid monolayer is more rigid and resist harsh environment.
6. Part of the envelope of a cell and it’s a monomolecular layer composed of identical proteins/glycoproteins. The functions vary from each organism. Example of functions: mechanical stabilization, protection, extra resistance, etc.
7. Different from bacteria, the flagellum of a Archeobacteria is built by subunits and not by necessity of protein caps.
1. Phospholipids associate by their amphipathic character. They have a hydrophilic head and a hydrophobic tail. This causes them to form a circle with the hydrophilic heads on the outside and hydrophobic tails on the inside.
ReplyDelete2. From the research I found, the hydrophobicity is a strong factor in not allowing the membranes to fuse. It makes the lipids strongly associate with each other. Some theories suggest curve is related, although that is still under discussion. Some results suggest that more of a curve will lessen the energy needed to fuse. Also, more PC is needed for fusion. This suggests that lipid concentrations and mixtures are needed for fusion/non fusion.
3. The way phospholipids associate in water does provide a theory that they could have evolved to form a membrane, but not a bilayer which most cells have. The problem for an evolution with phospholipids is that the do not form a bilayer in water. Many other components and attractions are needed to create the membranes we see on cells. Cell membranes are complex and require more than just phospholipids, but carbohydrates and proteins which aid in its structure. That does not mean it could not have evolved to that, but the way the bilayer functions is an important part to the life of a cell, which shows a more complex membrane is needed.
4. No, they do not. They form together in a circle with the hydrophobic fatty acid tails on the inside, but a second layer does not form on the inside creating tails facing tails and heads on opposite ends. Another layer forms around the first layer with head (outside), tail, head, and tail (inside). This is called a micelle. It’s layer represent that of an onion and not a bilayer.
5. The archaebaterial monolayers are called bolaamphiphile. They are called this because of their process of fusion between two phospholipid molecules. The structure ends up being one long chain of fatty acid with two polar heads at each end. It causes a higher solubility in water and a more rigid structure which gives it a better chance at surviving harsher environments. These membranes also have glycerol-ether lipids instead of glycerol-ester lipids. This causes an ether bond between the lipids which makes the lipids more chemically resistant. This would help in more acidic or alkaline environments.
6. The S-layer is a layer of glycoproteins that are a part of the cell wall. It contributes by providing stabilization, protection against viruses, resistance against low pH, and adhesion sites for exoproteins. It is not very conserved so structure varies by species. All of its possible functions are not known yet.
7. Archaebateria have a similar flagellum to bacteria, but they do not have an internal channel. This causes a problem for the assembly because no protein cap can be secreted. Instead, they use protein subunits that have changed to use peptide cleavage and add glycan. The problem is solved by the cleavage and the addition of glycan, although I would not say completely solved. I do not think this is the easiest or best of assembly compared to the bacteria or eubacterial cell.
1. Phospholipids associate themselves by their amphipathic character, which means that they have both hydrophobic and hydrophilic regions. To further explain this, phospholipids have the ability to be water-soluble yet also not water-soluble in different regions of its structure. The hydrophilic heads because they have polar groups and the ability to interact with hydrogen bonds. The hydrophobic tails are non-polar and uncharged so they do not dissolve in water. The head and the tail attach together in the phospholipids, making them a more compete molecule overall.
ReplyDelete2. I think the reason the membranes do not fuse has to do with being amphipathic. Due to the fact that they are mostly surrounded by water and looking to bond with hydrogen bonds or water molecules, this keeps the membranes from sticking to each other. Certain proteins or enzymes are needed in order to signal for the membranes to fuse with one another. It is possible that there are proteins in the bilayer that are causing the membranes to repel each other…
3. Evolutionists probably try to use the this theory that self-assembly of phospholipids created the first cell membranes. However, I know that cell membranes were created by our powerful God. Membranes are far too complex to say that they just evolved over time by assembling through a phospholipid. I understand the concept that phospholipids attract each other and create bonds with water and hydrogen, but they have many more characteristics that I’m not sure can be explained by this theory. A cell membrane can’t be formed in its entirety from water and phospholipids coming together.
4. Yes, they do because phospholipids need water to make membranes today. The bilayer is formed in a water-based environment because the hydrophilic heads are attracted to the water while the hydrophobic tails repel water. The tails do not come in contact with the water because they are on the inner layer. The membrane that is formed from this is basic and I would say that membranes today are more complex, but still have the same idea of formation.
5. Archaebacterial monolayers have the ability to the phospholipids together to form one molecule that contains two polar heads. The monolayers are thick and closely packed layers in the membrane. This allows the membrane to be more stable and protect themselves in more extreme conditions, such as more acidic environments. They also can withstand higher temperatures because their layer is thicker and more rigid.
6. The S-layer is part of the cell envelope that consists of proteins or glycoproteins and encloses the cell surface. It contributes to cell function because it is a protection for the cell against threatening bacteriophages, it stabilizes the cell membrane, and it provides adhesion sites for proteins as well.
7. Eubacterial flagellum is assembled from the power of a hydrogen or sodium ion. Archaebacterial flagellum are assembled by the use of ATP, and its subunits are added to its base rather than added to the tip like in eubacteria. The use of ATP to power the assembly makes more sense because the cell already contains so much ATP to use as energy. Hydrogen and sodium ions may need to be bonded and it makes it harder. Eubacteria also need a cap protein to be able to add its subunits. I think it is possible that eubacterial flagellums have a more complex process, making it easier for steps of the process to go wrong.
1. Phospholipids associate because of their polarity and amphipathic nature. The hydrophilic polar heads forming the top while the dryer- inner region are the hydrophobic non polar tails.
ReplyDelete2. Proteins placed throughout the cytoplasm and bilayers prevent any touching. These proteins are referred to as junctions, they also assist in intracellur communication.
3. I think the phospholipids' ability to self assemble supports some evolution, but not the origin of first cells. There is definitely room for cells to change over time through mutations and such. So self assembly gives room for variations but not origins.
4. When the phospholipids assemble they form into a circle of lipids, not a lipid bilayer. So the water forces the hydrophobic tails to move away and congregate while the hydrophilic heads go towards the water. The problem evolutionists have is that as stated earlier, the lipids do not form a bilayer.
5. Archaea bacteria monolayers tend to support life under extreme conditions because of the structure. The lipid layers can have multiple polar heads which create a more rigid and tense membrane. This stronger membrane aids the bacteria in survival.
6. The S layer is the outer layer of the membrane. It protects the cell ( most commonly bacteria) against other cellular predators. The s layer also acts as an adhesion and stabilizes the cell.
7. Archaean flagellum is similar to the rotating tail propeler of bacteria. The interesting thing is that the archaean flagellum is made up of multiple protein subunits.
1. Phospholipids are amphipathic. Their fatty acid tails are hydrophobic and try to avoid contact with water. So, the phospholipids gravitate toward each other and form a lipid bilayer, so that their fatty acids face inside, toward each other and away from the water. This is seen when you put phospholipids in water. Although, they won’t form a bilayer, they will form a spiral-like onion skin type formation called a micelle, because they don’t want to contact the water.
ReplyDelete2. When we studied the fusing of Hatena and Nephroselmis, we found that protein receptors in the membranes were a key factor in whether cells would digest each other or fuse. I would guess that this is the case here also. Even though the membranes are made of phospholipids, there are different types of phospholipids, and if they don’t match up, they probably won’t fuse.
3. No, because life consists of bilayers, and the self assembly of phospholipids only form spiral micelles. Also, the Bible is the ultimate source of truth, and the Bible says that God created life, and thus all cells also.
4. They do form membranes, but they are spiral, onion skin like formations, unlike the lipid bilayers found in living cells.
5. Archaea bacteria is different, because rather than having a lipid bilayer, it has a monolayer, which means that the tails of two phospholipids fuse together into a single molecule, making for a single-layer membrane. This makes the membrane for rigid and more durable, allowing it to survive harsh environments.
6. The S-layer stands for “surface layer.” It is the outermost layer in the membrane of a cell, and is composed mainly of glycoproteins. Some of its functions include giving the cell protection from external forces (i.e. bacteriophages, viruses, or low pH, etc.) and to give it structure and a binding site for other necessary things to attach to the cell.
7. Archaebacterial flagella lack the internal channel that Eubacterial cells use for the assembly of their flagella. Also, the Archaebacteria lack the cap protein that the Eubacterial cells use to guide the assembly of their flagella. Because they have no cap protein, Archaebacteria use another mechanism to make their flagella. Archae flagella are made of class 3 signal peptides, which are processed by a type IV prepilin peptidase-like enzyme. N-linked glycans, which are used to assemble the prepilin enzymes. This helps to solve the problem of not having a protein capstone.
1. Phospholipids self associate due to the hydrophobicity tendency of their nonpolar fatty acid ends. Because all nonpolar objects strive to avoid water, the phospholipids will always associate in such a way so as to have all the nonpolar sides facing away from the water.
ReplyDelete2. From my research, it seems that all fusion between membranes is not caused through collision (exclusively) but rather through hydrophobic tendencies, hydrogen bonding, and Van der Wall forces. However, it is known that some protein receptors also are crucial in membrane fusion. If none of these aspects are present when two membranes come together, there will be no merging of the two.
3. No. Whereas phospholipids, when placed in water, will form a membrane, these “membranes” are uniquely called micelles, because they create a phospholipid layer. In living cell membranes, the phospholipid layer is actually a bilayer, with two rows of phospholipids. This unique double layer is important with almost all cell interactions. And example would be hormones. Micelles, however, are not the same as phospholipid bilayers. Thus, the random association of phospholipids in water provides no proof toward an evolutionary process that makes use of it.
4. Going back to my previous point, it is very clear that phospholipids do not ever form correct biological membranes in the water. Instead of forming the bilayer that is crucial for cellular interaction, they form a simple single layer.
5. Unlike all other cells, archaebacteria do form a monolayer of phospholipids. This is done by taking the two layers and fusing them together into one layer. The added strength the membrane receives provides useful features that make it more desirable for these archaea. Specifically, having only one layer allows them to create a more ridged membrane that can help them survive in the extreme environments that archaebacteria are usually found in.
6. The S-layer is a layer of proteins or glycoproteins on the outermost part of the cell membrane. In archaebacteria, the S-layer is sometimes the only membrane it has. This S-layer provides many benefits to cells, some of which include protection from viruses and stabilization from outside forces.
7. Eubacteria form their flagellum by using protein caps to prevent the growing number of proteins that make up the flagellum from floating away. However, with an archaebacteria’s flagellum a different approach is taken. With three main groupings (anchor, hook, and filament) the archaebacteria’s proteins can quickly assemble the first stages while still inside the cell cytoplasm. Only on the final few steps is it required to construct while outside the cell. Thus, the archaebacteria seems to solve the problem of how to assemble and grow the flagellum outside the cell: construct the parts inside the cell, and only then push it out.
1. Phospholipids have Hydrophilic heads (attracted to water) and Hydrophobic tails that don’t like water and are therefore forced together. Hydrophobic ends are on the inside interacting with each other in a long chain of fatty acids and Hydrophilic ends are facing outwards interacting with water. This Amphiphatic nature along with two differently polarized areas (negatively charged phosphate in hydrophilic head) is how Phospholipids self associate. Phospholipids often occur with other proteins, as in the bi-layer of cell membranes.
ReplyDelete2. I think the amphiphatic nature of Phospholipids, along with Van der wall forces and hydrogen bonds have to do with the prevention of fusion with all nearby membranes. Proteins embedded in the membrane bi-layer are also thought to help in this. Proteins like receptors and signals (or even junctions – prevent contact) are used to prevent fusing with other membranes.
3. Not really. The Bi-Layer kills this theory. Phospholipids & Water don’t self assemble into a bi layer and with no bi layer there’s no life. The plasma membrane is far too complex (not just phospholipids, Cholesterol and protein too) to have evolved in this manner. Cells can’t survive without a membrane, the membrane would had to have been present since day one. whaa? creation and intelligent design maybe??
4. Yes & No. When Phospholipids are in a water environment (like the cytoplasm in the body) they naturally form into a bi-layer. This membrane is similar to that found in cell membranes but it lacks the proteins, cholesterols, and other macromolecules that truly make a cell membrane.
5. Unlike eukaryotes and bacteria (which both have glycerol-Ester lipids), the Archae’s membrane is composed of glycerol-Ether lipids.
This different kind of stronger ether bonded membrane helps the Archae have a more able resistance to extremophilic conditions (it is often found in regions of high temperature, extreme acidity, pressure etc.)
6. S-Layer: Surface layer on outside of the cell membrane wall composed mainly of glycoproteins (rather like chain mail). Contributions to cell funtion: protection against viruses, pathogens etc; contact binding site for bonding with other macromolecules (adhesion, collision etc); and general cell stability/protection. Other S-layer functions are still being discovered.
7. The makeup of the Archaebacterial flagellum is similar to the propelling tail of bacteria. This Archaebacterial though, lacks both the channel and protein cap used by Eukaryotes in flagellum assembly. The Archaebacterial assembles its flagellum by synthesizing subunits at the base (instead of the tip like eukaryotes.) The fact that the Archaebacterial flagellum can be assembled within the cell solves the problem of trying to assemble a flagellum from pieces of secreted eubacterial cell.
1. Phopholipids self associate in water because their hydrophobic tails move away from the water molecules and either towards each other or above the water. However the phospholipids with tails aimed toward each other will show self association, or micelle.
ReplyDelete2. Membranes have different phospholipids and overall different lipid composition, even though their structures are very similar. Due to these differences the membranes can distinguish itself from other membranes nearby and is able to fuse with membranes of its own kind.
3. The self assembly of phospholipids could be a possible explanation for how the first cell membranes evolved because we can easily see how the membrane is formed from bits and pieces. However there must be more information we are unaware about, such as the design of phospholipids and what purpose they have besides forming membrane layers.
4. When phospholipids form membranes in a water based environment they do not make membranes similar to the cell membranes we find in cells today because instead of forming lipid bilayers like normal cells, the phospholipids continuously come together which form multiple outer layers, known as micelle.
5. The monolayers of archaebactera are composed of six different ether lipids, based on condensation of glycerol and other complex polyols with two isoprenoid alcohols at 20 to 40 carbon atoms. The compounds without GD, GDGT and GDNT form monolayers that drop to as low as 2.172x10^-5 atm. This pressure drop causes the same drop in temperature that causes the film tension to remain constant. Lipids with the polar ends HL, GLB, or PLII form films that are more stable to compression.
6. An S-layer is a surface layer that is part of the cell membrane. It is composed of a monomolecular layer and encloses the whole cell. The functions of the S-layer are to protect the cell from bacteriophages, Bdellovibrios and phagocytosis, to resist against low pH, to act as a barrier against high-molecular-weight substances and to provide stabilization of the membrane.
7. Archaebacterial flagellum is similar to a bacterial flagellum but the archaebacterial flagellum is made up of protein subunits since it does not have an internal channel to secrete a protein cap.
1) Phospholipids self-associate due to the nature of the polarity of their parts. As stated in the blog post, Phospholipids associate when placed in water, which is made up of H2O dipoles. Because the phosphate head of the phospholipid is charged, it's naturally attracted to charged water molecules. However, because the fatty acid tales are not charged, they naturally avoid polar molecules…they become hydrophobic. When phospholipids are placed in an aqueous solution, the macromolecules bind together--the hydrophobic tails form a ring to be shielded from the polar water molecules while the hydrophilic heads form a barrier for the tails. That's why membranes form in a spherical orientation--what's on the inside cannot be touched by the outside.
ReplyDelete2) There are many more pieces of matter present in the cellular bilayer membrane than only phospholipids. It would be expected that phospholipids would indeed bind together upon contact with other cells because of their interactions in one cell. However, the proteins present on the outside of the membrane prevent cell membranes from fusing together. I would assume that protein receptors distinguish between other cell membranes and materials that need to be allowed into the cell membrane. Also, it has been thought that the presence of Cholesterol may play a role.
3) The natural phospholipid bilayer membrane is composed of many more entities than only phospholipids and water. To say that these are the only factors is to forget the presence of proteins and carbohydrates. Although the self-association of the membrane provides a THEORY for evolutionists, they likely cannot prove that it forms the exact bilayer found in living cells. We know that they cannot prove what isn't true.\
4) No, current living cell membranes are comprised of two layers of phospholipids with the tails facing each other to provide a hydrophilic middle region between the two layers. However, when phospholipids self-associate in water, they form what is called a "micelle," which is a spiral-like single-layer membrane.
5) Some archaebacteria membranes undergo a change in which the polar heads of phospholipids are fused together to form a more rigid structure, more effectively protecting the cell from the extreme conditions in which it lives. Whereas bacteria and eukaryotes are made primarily of glyco-ester lipids, archaebacteria monolayers are formed from glycerol-ether lipids which are more chemically resistable than glyco-ester lipids.
6) The S-layer of a cell is essentially a coating of proteins that surround the entirety of the cell surface, including the cell membrane. The S-layer is typically made up of identical proteins or glycoproteins. The S-layer of a cell aids in overall protection (especially from bacteriophages). Also, the S-layer provides the cell with adhesion points through which proteins link to the cell.
7) The archaeal flagellum is truly a magnificent creation. What the cell lacks, it makes up for in ingenuity. The archael flagellum lacks an internal column through which filaments are pushed out, so it has to be built through some other process. The flagellum has been discovered to be built from the base outward with various peptides. The protein assembly is assisted by glycans, which are polysaccharides…they seemingly keep parts from floating off before completion.
1.Phospholipids possess a hydrophilic head which has a special region that alters between different phospholipids and it will change with cell membranes or concentrations of specific head groups. Phospholipids also have two hydrophobic tails. Phospholipids arrange themselves into a sheet with two layers with their tails pointing toward the center when they are exposed to water.
ReplyDelete2. In order for the membranes to fuse, there must be particular transmembrane proteins present. Lipid membranes are constantly surrounded by water molecules which prevent them from fusing with other membranes.
3. Personally, I would say no. There would have to be a great amount of phospholipids present and the right structure to create the assembly that is seen in plasma membranes. Therefore, the first cell membranes were created by God.
4. They are alike because phospholipids associate freely into a bilayer due to their amphipathicity but their cell membranes do not possess only phospholipids. They also have cholesterol and different proteins inside of them which gives them structure.
5. It appears as though archaebacterial monolayers are able to bring phospholipids together to form two polar heads. The membrane is more stable and protects itself because the monolayers are thick and packed tightly inside the membrane.
6.An S-layer, or surface layer, is mainly found in bacteria and archaea. It is a part of the cell envelope and is made of a monomolecular layer which is composed of glycoproteins. The surface layer protein can represent 10-15% of the entire protein content of a cell.
7. The Archaebacterial flagella don’t have the cap protein or the internal channel. Because of this, the Archaebacteria is forced to use a different mechanism to make flagella. What helps to solve the problem of not having a capstone is that the Archae flagella are made of N-linked glycans which are used to create the prepilin enzymes.
1. Phospholipids are amphipathic, which causes them to tend to self-associate into larger macromolecules when placed in an aqueous solution. The polar regions orient themselves as to be with the polar regions of other phospholipids and the non-polar regions do the same.
ReplyDelete2. From what I can find doing some research it seems that along with proteins embedded in membrane internal forces play a factor is repelling other membranes that the cell comes in contact with.
3. The fact that phospholipids self assemble does provide some explanation for how first cell membranes came to be however this is not plausible. As we learned in class when placed in water phospholipids don’t form a bilayer, instead the shape they create is more of like an onion with many spiral looking layers. Therefore if this were to be the way in which first cell membranes evolved wouldn’t some membranes resemble that shape?
4. Like I said in the previous question, when phospholipids form membranes in a water-based environment their structure is not like the usual bilayer we see. Their membrane is a spiral shape not really forming a bilayer. These membranes that are created are called micelle.
5. Archaebacterial membranes contain an ether bond in the phospholipids of the membrane. Most other organisms contain an ester bond. The ether bond is stronger and resists chemicals, more which is why scientists think they can withstand chemicals more than other organisms.
6. An S-layer is the surface layer of some cell membranes that has a monomolecular layer that is made up of identical proteins. The S-layer helps protect the cell against damage. It particularly helps protect the cell from osmotic pressure that could damage the cell. The S-layer bulges when internal osmotic pressure increases which helps keep the cell stable so that it doesn’t allow leaks.
7 .In eubacteria the subunits are added to the top in a hollow channel. However in archaebacteria they do not have a hollow channel. This begs the question of how do they grow their flagella without the subunits floating away. Unlike the eubacteria, which add subunits to the top, the archaebacteria add the subunits to the base. The obvious problems involving the subunits floating away are solved in that it builds from the base up. However, I don’t necessarily think that one method is better than the other. Both ways of assembling flagellum are unique in their own ways.
1. Due to the hydrophobic and hydrophilic ends of the Phospholipids, they are able associate in a manner that keeps the hydrophobic tails of the phospholipids separated from water. When this happens it forms a sphere isolating the hydrophobic tails completely. The hydrophilic heads of the phospholipids hold intact with hydrogen bonds.
ReplyDelete2. In order for membranes to fuse there would have to be some sort of protein signaling to start to process. Perhaps the two hydrophilic ends of the membrane don’t allow fusion to occur without the help of proteins. The phospholipid bilayer could also have proteins that prevent other membranes from fusing with it.
3. The self-association of phospholipids only shows the intelligence of a creator. Evolution may use this as “proof” of how cells evolved but there is much more to the membrane of a cell. The bilayer and all the proteins that associate with it would have to be accounted for.
4. There are some characteristics that are similar to cell membranes we find today and there are some circumstances that aren’t. The phospholipids self associated similarly. The hydrophobic tails are kept disassociated from water by the hydrophilic heads of the phospholipids. The phospholipids in a water solution do not form a second layer like that of a micelle is found in some cells. This is a factor that isn’t similar.
5. The archaebacterial monolayer is rigid, closely packed, two-headed polar layer that protects it from harsh environments. This attribute is needed to protect the cell from its environment, letting it survive.
6. The S layer consists of glycoproteins. This layer protects the cell from invading virus, stabilizes PH, and perhaps prevents the membrane from fusing with other surrounding membranes.
7. The flagellum of the Archeobacteria is not made with a protein cap like that of other bacteria. This is due to the fact that Archeobacteria do not have an internal channel to derive the protein cap from. Instead the flagellum is made of protein subunits put together by enzymes.
1. The self-association demonstrated by phospholipids is explained by their intramolecular attractive tendencies. Individual phospholipids are amphipathic: Comprised of a hydrophobic, nonpolar end and a hydrophilic, polar end. When placed in an aqueous environment, the hydrophobic section of the phospholipid is simultaneously repelled from the water and attracted to the nonpolar ends of other lipids. Since water is ever present in the cellular environment, the hydrophobic ends of the phospholipids interact to form a membrane.
ReplyDelete2. The composition of the cell membrane prevents these same forces of attraction from sticking all cells together into a massive blob. According to some red-blood cell studies, phospholipids only make up 30% of the plasma membrane. The rest of the volume comes from other proteins and carbohydrates. These non-lipid parts of the membrane are not molecularly charged and could interfere with intra-cellular attraction.
3. The self-governing attraction of phospholipids could provide an explanation for how the first cell membranes evolved. However, it would be a very poor explanation. When phospholipids associate in water, they always form a micelle in which the hydrophobic ends congregate in the center of a ring of hydrophilic ends. True cell membranes necessitate a bilayer, in which there are two layers of phospholipids. Placed alone in an aqueous solution, phospholipids do not associate this way.
4. When placed individually into a water-based environment, phospholipids create a monolayered micelle. In the micelle, the hydrophobic ends of the lipids form an inner “nucleus” with a surrounding shell of hydrophilic ends. This type of membrane differs greatly from the fluid coverings found on cells. The true cell membrane is made of a bilayered, double row of phospholipids. This type of membrane has much more potential for complex functions than the micelle.
5. Some archaebacterial membranes are monolayered. Instead of having a double row of individual phospholipids, the archaebacteria fuse the hydrophobic tails of two phospholipids to make one long, double-headed molecule. Since these types of bacteria live in extreme environments, the unified, thick layer of phospholipids makes the cell more rigid and very durable.
6. Unlike the ordinary cell membrane, the S-layer is not comprised of phospholipids. Instead, various proteins form the rigid S-layer. This type of cell covering is extremely resilient and provides protection from the outside environment of the cell.
7. Like the eubacterial flagellum, the archaebacterial flagellum is driven by a tiny motor at the base of the stalk. This extracellular mechanism plays a crucial role in the cell’s locomotive abilities. However, there is a problem: How do the pieces stay in place during construction? To solve this problem, the two types of bacteria employ two different methods. With a hollow inner channel and a protein cap, the eubacterial flagellum builds itself by secreting pieces through the channel and to the cap. On the other hand, the archaebacterial flagellum is constructed from the base up with protein subunits. The bacteria must employ special processes to keep the parts in place. It appears that the eubacteria have done a better job of solving the problem as the archaebacterial flagellum becomes more unstable as it grows longer. Therefore, though the problem is solved, the process by which the archaebacteria approach the issue seems not as effective as other methods.
1. Phospholipids are able to self associate because of their amphipathic nature. Each phospholipid is composed of a hydrophobic and a hydrophilic end because of their polarity. The hydrophobic ends want to associate with the water molecules while the hydrophobic tails do not. This means that when placed in an aqueous solution, their hydrophobic ends associate with each other causing the hydrophilic ends to form a ring with each other forming a membrane so that no water can get to the hydrophobic section of the phospholipid.
ReplyDelete2. Phospholipids are not the only macromolecule involved in the formation of membranes and it would seem reasonable that there are certain proteins acting as receptors that can direct the phospholipid membrane as to what it should bind to and what not to bind to. This keeps the phospholipid from bonding to any other cell membrane that it come in contact with.
3. Forming a phospholipid bilayer is a much more involved process than simply the self assembling phospholipid molecules. Evolutionists want to believe that these phospholipids simply started forming cell membranes when placed in water by themselves. This theory is weak in that it does not take into account the carbohydrates or proteins that are used in the formation of a phospholipid bilayer and ultimately the creation of a living cell.
4. When phospholipids are placed into an aqueous environment, they associate themselves into what is called a "micelle." This micelle is a one layered or mono-layered covering of a central nucleus made up of hydrophilic ends of phospholipids. In this way it is much different than the very complex bilayer that we see in living cells today. The micelle is much more inferior to the bilayer formed in a normal cell.
5. This has to do with the types of bonds that the polar heads of the archaebacteria's membrane phospholipids create. When these phospholipids bond together they create a rigid cell wall that can resist most extreme temperatures and chemicals. These are called ether bonds. Most cells have ester bonds and but the ether bonds are much stronger and can resist the harsh conditions because of these rigid bonds.
6. The S-layer in cells, is a layer surrounding the entirety of the cell made of proteins or glycoproteins. This layer acts as protection for the cell from other entities and has many receptors allowing for messages to get into the cell. It can be thought of like TSA at airport security. They have to check everything before it is allowed to go through and be sure they have the right credentials to enter or "talk" to the cell.
7. Archaebacterial flagellum are different from eubacteral flagellum because they do not contain a cap or internal channel through which to build itself through. This means that it has to start from the base up. The question here is how does it keep the parts of the flagellum where they need to be? It does this through the use of glycans. These hold the peptides in place keeping them from floating away.
1) Phospholipids self associate to form a bi-layer, hiding their hydrophobic tails, made of long fatty acids chains and hydrocarbon chains, from H20 and to associate their hydrophilic polar head group, a negatively charged phosphate group, towards the H20. The hydrophobic tails repel the water and come together while the hydrophilic heads line up facing the water. So when the phospholipids are suspended in water, they come together and form different types of membrane structures.
ReplyDelete2) Cell Adhesion Molecules (CAMs) regulate when cell membranes can fuse together and when they cannot fuse. Some of these CAMs are Calcium-dependent, which could be related to the smooth ER, which regulates the concentration of Calcium ions.
3) A group of phospholipids could not just evolve together as many evolutionists might believe. The complex system would have to come from somewhere and be created. The formation of a membrane is far too complex to just evolve. The membrane is not only phospholipids but also, carbohydrates and proteins, thus creating a problem with just phospholipids and water forming a membrane.
4) They can from many different kinds of membrane structures like the micelle, the liposome, and the bi-layer sheet. The micelle is a spherical shaped phospholipid chain with only one layer. The liposome is also spherical in shape, but it is sphere with an empty middle. The bi-layer sheet is a thin sheet of two layers of phospholipids that connect together forming a continuous sheet that stretches into a spherical shape. One thing in common with these 3 different types of phospholipid formations is that they all seem to form spheres, which is a good way to make a continuous barrier that protects the hydrophobic tails.
5) Archaebacterial monolayers are different from a lipid bilayer because the tails come together, which are fused into a single molecule, and the heads attach on either end of the fatty acid chains creating the monolayer allowing it to be more rigid and withstand extreme environments.
6) The S layer is the outermost layer, made up of glycoproteins, of the membrane that protects the cell as well as supplying a binding site for things to attach to the cell.
7) The archaebacterial flagella lacks an internal channel like that of the bacteria, which in turn lack the protein cap used for assembly in the bacteria. The lack of the cap and internal channel cause the archaebacteria to build the flagella from the base unlike that of the bacteria. The archaebacteria also builds the flagella on the inside and then is brought to the outside where few steps are needed for final assembly.
1. The phospholipids have amphipathic tendencies along with a hydrophilic head and hydrophobic tail. Such a formation causes them to form with hydrophilic heads on the outside and hydrophobic tails on the inside creating the membrane layer.
ReplyDelete2. Has to do with receptors in the membranes and that there are different types of phospholipids and if they aren’t of the same type then most likely fusing will not take place.
3. First of all with my faith in the Lord I know what happened in the beginning of the world. The membranes are too complex for an atheist to say that it just evolved over time. Another problem is that there is no way that with only water and phospholipids that a membrane would come into being.
4. Yes I think so it has to do with the structure of the membrane layers. The layers are formed in water environment the heads are hydrophilic and attracted to water while the hydrophobic tails are repelled by water this is how the membrane layer is formed. Today there might be more complex membranes layers but the basic structures are the same.
5. The Archaebacterial monolayers are thick closely paced in the membrane which is the cause of higher stability and ability to life in extreme conditions. Even there layer is thicker and more rigid so that they can take higher temperatures.
6. The s-layer is glycoproteins in the cell wall that help by increasing the stabilization and protection against viruses. These are the main roles the s-layer plays but much study is yet to be done to know why God would create this structure.
7. They both are very similar but the Archaebacterial flagella lack the internal channel that the bacteria use also they do not have a cap protein. So the Archaebacteria have do a different way of solving this problem. So they use signal peptides and n-linked glycan’s to make the prepilin enzymes which in turn help with the construction of the flagellum.
1. Phospholipids tend to self associate with each other due to their amphipathic nature. When placed in a solution their hydrophobic tails bond together in a sphere, to avoid water, but their hydrophilic heads form an outer surface. This forms a single phospholipid membrane, a micelle.
ReplyDelete2. It could be that some proteins are involved in preventing separate membranes from combining. It is also possible that some type of Coulombic forces prevent membranes from fusing with others.
3. Probably not, because in most of the cells we are more familiar with is a phospholipid bilayer. Bilayers are very unlikely to develop by itself in natural conditions.
4. No, by itself, phospholipids in a water environment will form a single layered membrane known as a micelle. Most cells use a double layer of phospholipids.
5. In archaebacterial membranes, the phospholipid bilayer is fused into a single layer, this makes the membrane tougher, ideal for the extreme environments that are home to archaebacteria.
6. The S-layer is a part of the outer cell membrane. It protects the cell from predators and stabilizes the cell's form. It is made mostly out of glycoproteins.
7. In Eubacterial cells, the flagellum is assembled from the tip of the tail by means of a protein cap. However, Archaebacterial cells do not have the same resources, so it builds a flagellum by assembling protein subunits from the base.
1. Phospholipids form a bilayer spontaneously in an aqueous environment by arranging themselves so that their polar heads are oriented towards the water and the fatty acid tails are oriented away from the water. The reasoning for the orientation of phospholipids is as a result of their amphipathic nature, meaning they are both hydrophobic and hydrophilic.
ReplyDelete2. Phospholipids membranes must come in close contact with each other and their two surfaced must be partially dehydrated if they are to fuse together. The bound surface water normally present is what causes the lipids to repel each other, as a result of their amphipathic characteristic.
3. Evolution could use the changes found as a result of the self assembly process of phospholipids to explain how the first cell membranes evolved to what they are now. However, it is very unlikely that the first cell membranes would have developed by themselves in those natural conditions. There is too much ‘chance’ to account for and not enough explanation concerning the complex systems of phospholipid bilayer development.
4. Phospholipids form different membranes with different layers. A micelle in an aqueous solution forms a single layer, where the hydrophilic head region comes in contact with the surrounding solution, sequestering the hydrophobic tail regions in the center. A liposome resembles the same spherical shape as a micelle, but is empty in the middle. It’s membrane is artificial and is used for the purpose of moving drugs into the body in order to release them at a certain time. A bi-layer sheet can also be formed is a thin polar membrane made of two layers of lipid molecules.
5. Within some Archae, the lipid bilayer is replaced by a monolayer. The tails of two phospholipid molecules are fused into a single molecule with two polar heads. This fusion results in the membrane becoming more rigid and better able to resist harsh environments. Archae lipid tails are organisms that are able to survive in highly acidic environments.
6. An S-layer, also referred to as the surface layer, consists of a monomolecular layer composed of identical proteins or glycoproteins. This self-assembled structure encloses the whole cell surface. Its thickness is depended on the species. The S-layer is the outermost zone that interacts with the surrounding environment. The functions of the S-layer are diverse and vary with each species. The S-layer provides protection against bacteriophages, resists against low pH, acts as a barrier against enzymes, stabilizes the membrane, and provides adhesion sites for exoproteins.
7. The archaebacterial flagellum is superficially similar to the bacterial flagellum. Both consist of filaments extending outside the cell, which rotate and propel the cell. Archael flagellum lack the internal channel found in bacteria. As a result, they lack the protein cap used in the assembly of bacteria. Without the cap and internal channel, the archaebacteria begins forming the flagellum at the base. It begins inside and is brought outside to complete the necessary steps.
1. Phospholipids self associate because of their hydrophobicity. They have a hydrophilic head and hydrophobic tail. When placed in water, the hydrophobic tails cluster together to form a membrane, shielding themselves from the water.
ReplyDelete2. For membranes to fuse, there must be certain proteins. These proteins interact with the phospholipids, changing their hydrophobic nature and allowing the different membranes to mix.
3. While this may be a possible explanation, I believe that this is not the case. Cells in general are extremely diverse and involve many complex processes. So even if the self-assembly of phospholipids is a potential solution, there are so many more processes that cannot be answered by evolutionary thought. The complexity of cells points to the greatness and glory of our God, who, with just a few words, spoke these millions of cells into being.
4. Phospholipids formed in water based environments do not make membranes similar to the cell membranes we find today. When phospholipids are placed in water, the hydrophobic cells are pushed to the inside, as I talked about earlier. This is called a micelle. What happens when the lipid bilayer is formed is the hydrophilic tails are facing the outside and the second layer forms the exact same way, making a phospholipid “sandwich” with the hydrophobic tails on the inside.
5. Some archaebacterial monolayers are structured in such a way where the tails of two different phospholipids join together to form one single phospholipid. This helps contribute to life in the extreme because this extra strong layer helps protect the cell in harsh environments.
6. A S-layer is a layer made of identical proteins. It helps protect the cell from bacteriophages. It is also known to be an “adhesion site” for the cell.
7. The archaebacterial flagellum is made up of a motor and a propeller. Solving the problem of assembling the flagellum is an amazing example of the creativity and power of our God. While eubacterial flagellum contain a protein cap to help monitor the pieces and keep them from floating away, the archaebacterial flagellum lacks this cap and instead is forced to build the flagellum by adding the protein subunits to the base.
1. The process through which membranes associate themselves when placed in an aqueous solution is truly incredible. Phospholipids are ampipathic structures; they contain a polar head as well as a non-polar tail. This combination of hydrophilic and hydrophobic nature results in the phospholipids forming a spherical structure with the hydrophobic ends oriented toward the center. This allows the tails to satisfy their “fear “ of water.
ReplyDelete2. According to the research that I have conducted, membranes must come in contact in order to fuse together. The proteins on the extracellular portion of the membrane prevent any touching between to separate cells, thereby preventing the fusing of cells.
3. Phospholipids do in fact associate with themselves in an aqueous solution. However they primarily do not form bi-layers, which is necessary for life. Another main issue is the fact that carbohydrates and proteins are not present in the membranes, which are critical in the sustainability of life within the cell.
4. No, they do not because although membranes do associate themselves, the majority of them are not bi-layered phospholipids. Which are the membranes required to maintain the interior environment necessary to maintain life. Rather than forming a bi-layer, they form layers of single layered membranes, otherwise known as micels.
5. The archaebacterial monolayer ‘s ability to conform to its extreme environments is incredible. The fact that it is able to form a rigid and firm membrane is essential in its ability to stay alive. Even the glycerol-ester bonds they are composed of are able to resist chemical reactions allowing it to maintain its rigid structure.
6. The S-layer within the cell wall is composed of glycoprotein’s, their functions are to provide structure, defend the cell against viruses as well help the cell resist changes in pH, especially when the pH becomes more acidic.
7. The difference between archeobacteria’s flagellum from that of eubacterial cells is that it does not have the protein cap found in eubacterial cells. Rather it constructs its flagellum by organizing small protein subunits.
1. Phospholipids self associate due to their amphipathic character. This means that they have both a hydrophobic and hydrophilic regions. The phospholipid head is hydrophilic and the tail is hydrophobic. This causes them to form a sphere with the heads on the outside and the tails on the inside.
ReplyDelete2. There are different proteins on and imbedded in the membrane. They are, in part, what determines whether certain membranes will fuse with others or not.
3. While it might not be a totally faulty thought, the idea that phospholipids created the first cell membrane is not the best argument. Cell membranes are made up of more than just phospholipids, such as different kinds of proteins.
4. They are similar in the sense that it is possible for them to form a bilayer, however they lack the complexity that living cells do (proteins, carbs, and cholesterol).
5. With an Archaebacterial Monolayer, the archaea fuses the tails of the two independent phospholipid molecules into a bolaamphiphile, which is a single molecule with two polar heads. This fusion allows them to endure more harsh environments.
6. The S-layer is the outermost part of the cell membrane and is often found in bacteria. It is composed of proteins and glycoproteins. This outer layer is built by self assembly.
7. The archeabacteria flagellum is quite similar to the bacterial flagellum. However there are a few differences. Unlike a bacterial flagellum, the Archeabacteria flagellum grows due to the addition of subunits at the base. It is also powered by ATP instead of H+ ions.
1. The Phospholipids associate with each other because they are Ampipathic, meaning that they have a polar and non-polar region. This allows them to easily self associate in liquid cell environments. The positive and negative regions align and the bilayer is formed as a result.
ReplyDelete2. It has been observed in study, that when phospholipids in a cell come into direct contact with each other, they will fuse to form one bilayer. Therefore, there must be some object to separate them. The solution to this is the carbohydrate and protein groups that protrude from the bilayer. These external structures prevent contact and therefore prevent formation.
3. No, it is not a plausible explanation. When phospholipids are placed in water by themselves, they do not form a bilayer. Instead, they form an onion skin-like object with only one layer. Without this bilayer, the cell could not be occupied by the essential organelles for life and existence.
4. As stated in the last answer, they form a single layered, spiral shaped structure. Therefore, the shape that they form is not at all similar to cell wall of cells.
5. Due to the monolayers that the Archaebacterial possess, it is able to live in extreme pressures. When exposed to such conditions, the bilayer membrane can collapse upon itself, forming the protective monolayer. This protects the species from extreme conditions and maintains proper pressure in extreme environments.
6. The S-layer is a layer of proteins and glycoproteins often found on the cell envelope of bacteria. While it has a large range of functions, some of the most popular include the following:
a)Protection against Bacteriophages and phagocytosis
b) Barrier against lytic enzymes
c) Resistance to low pH
7. In the first few weeks of cell biology, we learned that eubacterial cells develop their flagellum by a unique method. Beginning at the base, a hollow, stalk-like structure is formed and built upon at the tip. Sub-units are pushed through the hollow channel in the middle and are assembled at the tip. In contrast, archaebacteria begin to form the flagellum at the base and continue this process until finished. Thus the system does involve fewer parts, but the issue of complexity still exists. Thus to solve the problem of complexity, the parts are secreted at the base of the flagellum. While each system is unique, each shows the amazing design of our Creator.
1 Phospholipids have hydrophobic tails and hydrophilic heads, giving them a dual nature called amphipathic. They hydrophilic heads interact with the water molecules, forming hydrogen bonds, yet the hydrophobic tails do their best to stay far away from water. Therefore, the similar ends are attracted to one another and they form circular layers.
ReplyDelete2 Because the hydrophilic ends love water and want to form hydrogen bonds with the water molecules, this attraction is stronger than the attraction between two amphipathic bilayers, even though the outer layer of the cell membrane is also hydrophilic. The stronger attraction makes it less desirable for the cells to fuse as opposed to being individual cells and retaining their hydrogen bonds with the water molecules.
3 Yes, this could be a possible explanation of how the first cells were formed evolutionary, although we know this to be false because God created the first cells. However, when phospholipids are added to water, they form micelle arrangements, in other words a spiral membrane, not a complete circle. Other chemicals must be present for a circular arrangement to form.
4 As I stated in my previous answer, when phospholipids are placed in water they form spiral arrangements, known as micelles. They aren’t structurally identical to the membranes we find today; in fact, these micelles cannot function properly as cells because they aren’t completely closed off. The function of the cell would be completely different.
5 Explore the structure of the archaebacterial monolayers. How does this contribute to life in the extreme? Archaebacterial monolayers are phospholipids with two polar, or hydrophilic, heads instead of one. These monolayers are just that, single layers of these cells, and because their structure is more rigid and enables to cell to live in more acidic environments. These monolayers can survive in more extreme conditions, which according to evolutionary thought, would be necessary when life first arose.
6 The S-layer is the part of the cell that contains membrane proteins and encloses the cell surface. Membrane proteins enable the cell to communicate with other cells, protect itself from foreign invaders, stabilize the membrane, and provide adhesion sites for other proteins that cause changes inside the cell.
7 The eubacterial flagellum is an acid driven motor and is actually less complex than an archaebacterial flagellum, which consists of an actual motor. From an evolutionary standpoint, it should be the opposite, since the current belief is that archaebacteria preceded eubacteria. But we know that God created these complex micro-machines, and it is very possible that He made them in this way as to confound modern evolutionary scientists.
1. Phospholipids self associate by forming a bilayer, with one side being hydrophilic and the other side being hydrophobic, meaning they are amphipathic. The hydrophilic head is on the outside and the hydrophobic tail is on the inside. Therefore in aqueous environment, the hydrophobic tails cluster together to get away from the water.
ReplyDelete2. I think there are proteins that are acting as a receptors, signaling which phospholipids to fuse with each other.
3. When phospholipids self assemble, they do not form a bilayer, they only form a micelle. Therefore that is not a plausible theory for the evolution of life. Since as Christians we know that God created life, there is no evolutionary theory that would be plausible of how life was created.
4. No, in a water based environment they form a micelle, which is single layered, whereas the cell membranes we see in cells today are made up of complex bilayers.
5. Archaebacteria do not have a bilayer, they have a monolayer. This monolayer is created by the phospholipids fusing their tails together, to form one molecule. This action allows the bacteria to withstand harsh and extreme conditions.
6. The S-layer is a cell wall that is completely made up of glycoproteins. This layer functions as protection for the cell and helps stabilize the cell as well.
7. Instead of using a cap protein to make the flagellum like Eubacteria, the Arcaebacteria uses protein subunits to form the flagellum from the base upward.
1} Phospholipids are composed of two hydrophobic fatty acids and a glycerol connected to a hydrophilic phosphate-containing group. Water is prevented from making hydrogen bonds, reducing free movement and causing more order. The water molecules create a shell around the hydrophobic lipid as they are repelled from the water and form a clustered layer. By forcing the lipids into a bilayer, the tendency toward free movement is fulfilled. Therefore, phospholipids self-associate in water due to the entropy effect water seeks to reduce, surrounding the phospholipid.
ReplyDelete2} Hydration repulsion between the hydrophilic lipid head groups prevents the fusion of membranes with each other. The dipole-dipole interactions between the lipids of the bilayer bring about forces known as van der Waals forces. As molecules come closer, the attractive forces of the lipids becomes greater as well as repulsion against what is approaching.
3} I do not believe that the self assembly of phospholipids could be a plausible explanation for how the first cell membranes evolved because many, many chemical foundations would have needed to be in place- far more than a mere primordial soup could account for. How would the dipole forces have been established? How did the glycerol, phosphate, and fatty acids components associate just right into a complete phospholipid? Over thousands of years, would the very first phospholipid have chemically survived the repulsive affect of water while being close enough to the second phospholipid formed to begin to bond?
4} The membranes phospholipids form in a water based environment differ from cell membranes because cell membranes are fluid or semi-permeable, whereas the phospholipid membrane has forces that prevent it from fusing, etc.
5} Archaebacteria have a monolayer formed of tetraether lipids. Ester lipids are not susceptible to degradation at alkaline pH and enzymatic break down by phospholipases or harsh high salt environments.
6.} The S-layer is part of the cell envelope, consisting of a monolayer of glycoproteins. The S-layer protects against damage from bacteriophages, phagocytosis, lytic enzymes, low pH; it also provides adhension sites for exoproteins and periplasmic compartments.
7.} Possibly the problem of assembling a flagellum in the archaebacteria could be considered as more feasible; however, if the flagellum is used for movement, how would the bacteria have survived without it in it's intermediate state- before the flagellum was fully formed? Or if the archaebacteria were able to live symbiotically and obtain movement from another bacteria, where would *that* bacteria have come from? Again, the enormous issue of irreducibly complex systems and the unsurvivable "middle" state cannot be compensated for in evolutionary thinking.
1)Phospholipids self-associate because of the bi-layer. They push their tails in the inside so that they are hiding them. Their head are negative, which make them attractive to water.
ReplyDelete2)What prevents the membrane from fusing together because of its structure being hydrophobic. With the water clumping together it will prevent the membranes from fusing together.
3)For the explanation that phospholipids being the first dell is probably hard to explain. Start a cell without first having a membrane is what would strike me. So the membrane would have to form some kind of DNA to get the process/foundation started.
4)Yes, the formation that the phospholipids membrane cell that they form is similar to cells today. Compared to us humans who are a water based environment, we can assume that are membranes are similar to phosphlipids. Now there may be some differences between salt content, but nevertheless the membranes are still similar.
5)The structure of the archaebacterial monolayers is that is consisting of two nonequlivent polar heads. It has the ability to expand it thickness content of its shape. The ability to survive a wide range of tempature. It makes it extreme because it can stand the harsh environment that surrounds it.
6)The s-layer is found in the cell membrane/cell wall of bacteria, which are commonly found among Achaea. This layer is part of 10-15 percent of the cell content. With its structure it is able to enclose the whole cell surface
7)The Archaebacterial flagellum is similar to a rotating tail in bacteria. With the understanding that it has multiple protein subunits. Making it harder to find to understand its detail
1.Phospholipids self-associate due to the fact that they have a polar hydrophobic fatty acid tail and non-polar hydrophilic head. Because of this the heads of the phospholipids come together forming a sort of boundary in part to protect (if you will) the polar tails but also because of their attraction to the water molecules.
ReplyDelete2.Because the external part of the bilayer is hydrophilic it is attracted to the surrounding water molecules and this force of attraction may override the attraction that the bilayers of different cells have for each other. It’s also important to note that each cell has proteins in their membrane which act as receptors. These receptors separate other membranes from fusing together because they protrude out of the membrane preventing direct contact.
3.This is not a plausible explanation for the first cell’s existence. Bilayers are mandatory for life to exist and as explained in class, when phospholipids are put into a water solution they do not form a bilayer. Rather, a circular layered composition is created called a micelle.
4.No they do not, as stated above they lack the ability to form a bilayer and the protein receptors that are necessary for a membrane to communicate and to provide stabilization are not present.
5.Archaebacterial monolayers are capable of withstanding harsh conditions such as extreme cold or heat. The fact that they have one layer where their tails and heads attach together makes their structure more solid. This stronger membrane can adjust to the outside conditions that impose upon it. Bilayers have a more fluidic membrane making them more vulnerable to extreme conditions.
6.S- layers are surface layers that are commonly found on bacteria. It is part of the cell envelope and is a monomolecular layer composed of proteins and glycoproteins. The S layer has many functions but ultimately its purpose is to protect and maintain the cell. It protects the cell from bacteriophages and phagocytosis, shows resistance to low pH levels and aids in the adhesion of proteins.
7.In Eubacterial cells there is an acid driven motor that propels the flagellum. When this motor is created it pushes outward as it grows in length until it is completely formed. It is able to do this by the use of a protein cap that holds the pieces of protein together. In Archaebacterial cells they lack this protein cap and ability to form a flagellum in this manner. Instead, the flagellum is built from the surface base upward by subunits of protein that stack together.
1. Phospholipids have a amphipathic nature which means they have a polar region and a non polar region. In the case of the phospholipid the head region is hydrophilic and the diglyceride is non polar. Because of this construction, the hydrophilic heads and hydrophobic tails cause the phospholipids to associate. Due to the association, phospholipids form a bilayer which is a really important reason why they associate.
ReplyDelete2. The cell membrane contains and abundance of proteins all around. There are proteins on the membrane that work for the fusion of two membranes, when the membranes recognize each other they have an attraction that draws the two membranes to each other, initiating the fusion. However, if the two cell membranes are not meant to fuse the proteins will not attract, instead they will repel the other membrane.
3.When phospholipids are placed into a polar solution they form micelles. Micelles are made up of phospholipids arranged in a circular arrangement, with out a bilayer. Through this we can see the nature of phospholipids. In a cell membrane we have a bilayer, so if the phospholipids just came together their nature would be to create micelles, not bilayer membranes. This shows us that God created the bilayer and complex membrane we know of today.
4.When phospholipids are placed into a water based environment they create micelles. Which is similar to the membrane, because the phospholipids associate in the same manner, however, they do not form a bilayer, which makes them different from the cell membrane.
5.In an archaebacterial monolayer the phospholipids form a thicker membrane, because of the double polar head they contain. The phospholipids are associated with ether bonds, making the association even stronger, which allows the archeabacteria to survive in extreme environments.
6.The S-layer is a monolayer composed of proteins. It is commonly found in bacteria and in archaea. Since this is the outermost layer it has the most interaction with the outer environment, it has a range of functions. Some of these functions include: protection from bacteriophage, resistance against low pH, etc.
7.The archaeal flagellum is very similar to that of the the bacteria. The major difference is that instead of subunits going up form the central pore, like in bacteria, in archeabacteria the subunits are added at the base.
1. Phospholipids self associate because when they are placed into an aqueous solution they are amphipathic meaning that they have a hydrophilic head due to the negatively charged phosphate and a hydrophobic tail composed of fatty acids. Depending upon the solution they are placed in they will form micelles or inverse micelles due to their amphipathic nature which serves as the mechanism for the phospholipids to be orientated and associated into spheres. The primary force behind their self association is the hydrophobic force that becomes prevalent after the critical micelle formation concentration is reached creating entropy conditions that causes the formation of micelles to be more stable.
ReplyDelete2.From my research, I would have to conclude that it has to with SNARE proteins and their role in membrane fusion. I think that the SNARE proteins in their varying distinct locations serves to control the initial fusion of the membrane and to serve as a sort of authenticating source to validate the instigation of the fusion of membranes. I think it is these SNARE proteins and this process that assures that membranes bind only with only the proper membrane.
3.Self assembly of phospholipids serves to explain inherent structural and chemical properties found within the phospholipids but serves only to show what already exists. This inherent structure causes the formation of micelles and serves an important function in the formation of cellular membranes but does not support a progression or evolution merely a validation for a design that has been set into place.
4.Phospholipids self associate into micelles which demonstrate the basic structure of the cellular membranes but are vary different from cellular membranes. Phospholipids form a uniform cellular membrane whereas the cellular membrane is complex and diverse composed of many varying protein with distinct functions. Phospholipids serve as an example of basic membrane behavior but fail to replicate or fully explain the complexities of the cell.
5.The structure of the archaebacterial monolayers contributes to their ability to withstand an extreme life in that unlike the typical glyco-ester lipids that compose eukaryotes and bacteria, archaebacteria bacteria membranes are composed of glyco-ether lipids. This difference results in the formation of ether bonds that help the archaebacteria to resist extreme changes in temperature and chemical extremes. The branching and formation of rings within lipid tails also serves to prevent the membrane from losing molecules at a higher temperature making it more better designed for extreme environments. Another key function that supports this extreme life is the formation of a bolaamphiphile from the tail of the lipids in a monolayer thus making creating a more rigid membrane that is more resistant to the extremes.
6.The S-Layer is a layer composed of proteins or glycoproteins and functions for many bacteria as their outermost layers. This results in the layer serving as the primary point of interaction with the external environment making it serve several key functions such as protection, provision of binding sites and to stabilize the structure as a whole. The function of the S-layer is best understood by looking at it’s structural design and God’s intentionality in having it be in this point of interaction with the external environment as form supports function.
7.Eubacteria uses a capping protein HAP2 to create stability as the flagellum is constructed from the tip down this differs from that of the archaeal flagellum in that the archaeal flagellum is assembled from the base through the use of subunits. This is a different method for creating a different type of flagellum so each method has been crafted to best serve their intended purposes so I think the archaebacteria has a different mechanism that appears to avoid many of the problems that typically face the formation of an archaebacterial flagellum so in that sense it has solved the problem.
1.) Phospholipids form a bilayer because of their hydrophobic tails. The lipid bilayer keeps the fatty acid tails inside the bilayer, so that they will not make contact with the water on the outside of the lipid bilayer.
ReplyDelete2.) I think the reason that membranes do not just fuse with other membranes is because of the proteins present on the outside and in between the lipid bilayer. I assume that the protein receptors know what not to bind to.
3.) The bilayer is essential for life, therefore, it does not support the theory. When lipids are put in water, they form more of a onion skin shape,. They do not go into a lipid bilayer, which is what would be necessary for the evolution of cell.
4.) The membranes that phospholipids make when they are in a water based environment is not a bilayer, but a micelle. It forms a spiral micelle that is more like an onionskin, rather than, a bilayer. The hydrophobic talk of the phospholipids goes into the middle of the circular shape they from while the heads are just on the surrounding.
5.) Archaebacteria does not have a bilayer, but a monolayer. In a monolayer the tails of two phospholipid molecules are fused together to make a single molecule that has two polar heads. This fusion makes it so that this bacterium has a rigid monolayer and can better survive in harsh environments.
6.) The S-layer is part of the cell-envelope that is tends to be found in bacteria. The S-layer is made up of glycoproteins and encloses the whole cell. Different functions of the S-layer include: protection against outside invaders, stabilizing the membrane, and resisting against low pH.
1 Why and how do phospholipids self associate? Phospholipids are a basic component of cell membrane, it’s known as amphipathic which contains two hydrophobic tails and a hydrophilic head. These phospholipids can replicate themselves when they came to contact with water. The hydrophobic tails rearrange themselves into a two layer called lipid bilayer; a sheet like structure with center contains almost no water. On the other hand, the hydrophilic phosphate head point out to the water on the other side to protect the membrane from random diffusion of other substances. This structure of phospholipids is important to keep cells from grabbing to each other or stuck to each other which will make it impossible for us to stay as individual; we might become asymmetry or all mix together like water.
ReplyDelete2 What prevents membranes from fusing with all other nearby membranes? Since membranes are made of phospholipids (also called amphipathic), the membranes are kept from fusing with all other nearby membranes due to its hydrophobic and some of how the viruses work. On the other hand, most cell membranes made of proteins, carbohydrates, etc that also keep the cell from fusing together because of their charge as well. So if any viruses want to enter the membrane, it has to have a specific fusion protein like the cell to attract cell membranes to them.
3 Could the self assembly of phospholipids be a possible explanation for how the first cell membranes evolved? No, the self assembly of phospholipids is not a possible explanation for how the first cell membranes evolved. Because a cell needs a large amount of phospholipids for its membranes, therefore, a very large amount of phospholipids would be needed along the evolution of the cell. It has to do with the design that the cell has the ability to form its own membrane. However, if phospholipids can explain how cell evolved, then how can cell evolved without membrane in the first place?
4 When phospholipids form membranes in a water based environment, do they make membranes similar to the cell membranes we find in cells today? When phospholipids form membranes in a water based environment, they do make membranes similar to the cell membranes we find in cells today. Because of its dual nature of hydrophobic fatty acid tails that repels the water and hydrophilic phosphate head that attracts the water and form a bilayer structure of membrane. This is how the nowadays cell membranes look like.
ReplyDelete5 Explore the structure of the archaebacterial monolayers. How does this contribute to life in the extreme? Archeabacterial monolayers using isopreniod sidechain that is a long chain with multiple side-brances or cyclopropane/cyclohexane rings in contrast to fatty acids found in other organisms’ membranes, which have straight chains with no branches or rings. This branched chains help prevent Achaean membranes from leaking at high temperatures. The archaebacterial monolayers is when archaea fuse the tails of the two independent phospholipids molecules into a single molecule with two polar heads which make their membranes firmer and better to resist the harsh environment.
6 What is an S-layer and how does it contribute to cell function? S-layer (Surface layer) proteins are crystalline arrays of proteinaceous subunits that are present as the outermost component of the cell wall in several bacteria (Lactobacillus species). It provide mechanical stabilization for the cell. Other than that it is not known/understood yet the true function or role of it in the antimicrobial activity of certain lactobacilli. But there are some studies that hypothesize that the S-layer proteins antagonize Salmonella Typhimurium (S. Typhimurium) infection. (http://mic.sgmjournals.org/content/157/9/2639.full)
7 We discussed the problems inherent in trying to assemble a flagellum from pieces secreted from the eubacterial cell. How is this problem solved in the archaebacterial flagellum? Or is it solved? The eubacterial flagella are powered by a flow of H+ ions (or Na+ ions), unlike archaela flagella are almost certainly powered by ATP and the torque-generating motor that powers rotation of the archaeal flagellum has not been identified. The different between the flagellum behaviors of both bacterial, the thickness of the flagella, and the sequences are different. Therefore, it seems like the problem is not solved.
1)Phospholipids when placed in water associate to protect their hydrophobic tails for the water and to allow their polar head to interact with water. The polar head has a negatively charged phosphate that is attracted to the positively charged H+ ion of water; the fatty acid chains are made-up of hydrocarbon chains. The hydrogens that are attached to the carbons in the fatty acid chains have already bonded once, so they won’t bond again making the chain non-polar (hydrophobic). The Phospholipids create a circle to allow for less surface area on the inside to not react with the water as much and greater surface area on the outside to interact with the water. When you have a bi-layer it doesn’t allow the hydrophobic tails to touch water at all making them even more content.
ReplyDelete2)The fusion process. 1st, the membranes must be within several nanometers. 2nd, the two bilayers must come within a few angstroms of contact (to achieve this, the two surfaces must become at least partially dehydrated). 3rd, there needs to be a destabilization must form between the two bilayers. And there is a theory that there is a highly curved stalk formed between the bilayers; they think this explains why the phosphatidylethanolamine, a highly curved lipid, promotes fusion. This shows why cell membranes don’t normally fuse together because of water molecules being constantly around them. The hydrophilic head would always have an attraction to water so it would take a lot of energy to separate the two. So, it doesn’t seem likely that they could merge.
3)Yes, it could be a possible explanation for how the fist cell of membranes evolved. (It doesn’t mean we have to believe it as creationist, but we can look into it.) Phospholipids do create a formation that protects their hydrophobic tails from touching water – they create a circle. But it isn’t a bilayer with proteins and carbohydrates infused into it. A cell membrane is more elaborate, but for an evolutionist, they are just giving an hypothesis—an explanation that seems plausible at a generic level.
4)No, it is called a micelle. It is described as onion layers. It is a spiral of hydrophobic heads facing outwards and continue spinning like a conch/snail shell.
5)There are two structural reasons why they can survive in a life that is more extreme. Archaebacterial monolayers have ether bonds rather than ester bonds between the phospholipids making them chemical resistant more so. The monolayer is a fatty acid with two hydrophilic (polar) heads at each end. Because of the hydrophobic heads being located at the ends it makes it more stable, structured, rigid formation which allows them to sustain high temperatures and not break apart in an extreme environment.
6)The Surface layer “S-layer”, is the outer layer of the membrane which encloses the cell’s surface. It is made mostly out of glycoproteins. Some of the functions of the s-layer: it protects the cell from foreign adversaries like bacteriophages or against low pH. It also gives internal structure and stability, and has attachment sites for proteins to dock.
7)A eubacteria adds its subunits to the top of an internal channel by a cap protein that doesn’t allow the subunits to float away. The Archaebacteria doesn’t have an internal channel nor a cap protein, but it bonds its subunits at the base. The eubacteria is described as having a motor, shaft, propeller; the archaebacteria is a motor with a combined shaft-propeller.
1.Phospholipids associate themselves by amphipathic (amphi means both), because they have a dual nature (part polar and part non-polar). The head of the phospholipid is very polar and therefore likes to associate with water (hydrophilic; the charged, polar head groups form the particle's surface making it perfectly soluble in water), while the tail of the phospholipid which is composed of the two fatty acid chains are very non-polar and tend to avoid water (hydrophobic; the large hydrocarbon tails aggregate in the center of the particle excluding water from contact with the non-polar structures) and associate with other hydrocarbon chains. Thus, this characteristic causes phospholipids to self-associate into large macromolecular complexes in an aqueous environment.
ReplyDelete2.Proteins where exist on the outside of the membrane or cytoplasm and which are described as receptors prevent membranes from fusing with all other nearby membranes. These play role as preventing or touching of other membrane as junction.
3.In my opinion, the self assembly of phospholipids could not be a possible explanation for how the first cell membranes evolved. In an aqueous environment, phospholipids do not form bi-layers; put into water, they form micelles and predominantly spherical membrane structures called liposomes or vesicles and at the air-water interface, phospholipids form single layers, or monolayers, with their polar head groups solvated in water and their hydrocarbon tails sticking into the air (non-polar or low dielectric medium). In addition, there are no presences of carbohydrates or proteins that are showed in the membranes. Therefore, evidences for accounting the formation of the cell membrane that relates to the self assembly of phospholipids are lacked.
4.No, they do not make membranes similar to the cell membranes we find in cells today when phospholipids form membranes in a water based environment. They form micelle (the polar head groups stick out, facing the water, while the center is full of hydrophobic tails that exclude water) which is spiral shaped, onion skin-like single layer formation and gives the structure of a sphere to the miceller aggregates, instead of forming bi-layers as explaining in the previous question.
5.The structure of the archaebacterial monolayers contributes to life in the extreme by the glycerol ethers of archaebacteria, which constitute the hydrophobic residues of the polar lipids and consequently the membrane interior are diphytanylglycerol diethers or dibiphytanyldiglycerol tetraethers. Either or both glycerol ether structures may be present, depending on genus. The tetraethers of the thermoacidophilic archaebacteria are more specialized in that the dibiphytanyl alkyl chains may contain 1 to 4 cyclopentyl rings. As a consequence of the presence of the tetraethers which can span the membrane, archaebycterial membranes can exist as a lipid “monolayer” rather than the usual lipid bilayer. Thus, the ether bond, compared to the ester bond found in other organisms, is more chemically resistant and the reason that the archaebacteria can survive in harsh environments.
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ReplyDelete6.An S-layer (or surface layer), monomolecular crystalline arrays of proteinaceous subunits, is the most commonly observed cell surface structures in prokaryotic organisms such as bacteria and archaea and made up of proteins and glycoproteins in a hexagonal symmetry. They are highly porous protein meshworks with unit cell sizes in the range of 3 to 30 nm. Also, they are mostly 5 to 25 nm thick, and they reveal a rather smooth outer surface and a more corrugated inner surface. Since S-layers are monomolecular assemblies of identical subunits, they exhibit pores identical in size and morphology. In gram-positive bacteria and archaea, the S-layer subunits are linked to the peptidoglycan-containing layer or to the pseudomurein. In gram-negative bacteria, attachment involves components of the outer membrane. In archaea lacking a rigid wall layer, S-layers are the only wall component, being closely associated with the plasma membrane. Moreover, S-layer contributes to cell function by working as precise molecular sieves, providing sharp cutoff levels for the bacterial cells, the adhesion of the bacterial cells to the intestinal epithelium, stabilizing the cell, and fulfilling a shape-determining or shape-maintaining function.
7.This problem is solved in the archaebacterial flagellum by that archaebacteria lacks the internal channel and is not made with a protein cap. Archaeal flagella’s function is like their bacterial counterparts, with elongated stalks driven by rotatory motors at the base; the motors themselves are powered by the electrochemical gradient across the membrane. Archaeal flagella are constructed from addition of subunits at the base. Then, these make archaebacteria and eubacteria which has flagellum that uses a protein cap and internal channel for the assembly of the flagellum different to each other. Therefore, archaebacterial flagellum is made of protein subunits, N-linked glycans which are used for creating the prepilin enzymes.
1. Phospholipids are amphipathic and have two polarized regions: hydrophobic and hydrophilic. Due to their amphipathic character they are able to disassociate. They contain a hydrophobic head and a hydrophilic tail. This allows them to form a circle with the hydrophilic tails on the inside and the hydrophobic head on the outside. Since the hydrophilic heads like water and hydrophilic tails don’t they are forced to be bonded together.
ReplyDelete2. Membranes have different phospholipids, and also various lipid compositions. In order for membranes to attach to nearby membranes, those nearby membranes have to contain similar transmembrane proteins. Lipid membranes are surrounded by water molecules which prevent these different membranes from fusing together.
3. In my opinion I don’t believe phospholipids are the explanation for how cell membranes evolved. Life if composed of bilayers, and the self-assembly of phospholipids only form spiral micelles. There would have to be a large amount of phospholipids present and the right self structure to even make this possible. Therefore, in my opinion the first cell membranes were created by our creator, God.
4. Yes I think this is possible. It all has to do with the structure of the membrane layers. These layers are formed in water environment. The heads are hydrophilic while the hydrophobic tails are repelled by water, This explains how the membrane layer is formed. Even today, there might be the existence of more complex membranes layers. Although the basic structures are still the same.
5. Most archaebacterial monolayers are structured in a unique way. This structure demonstrates the tails of two different phospholipids joined together to form one single phospholipid. This helps contribute to life in the extreme because this extra strong layer helps protect the whole cell in extreme conditions.
6. An S-layer is a part of the cell envelope commonly found in bacteria. It is also found among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins. It helps protect the cell from bacteriophages.
7. The difference between archeobacteria’s flagellum from that of eubacterial cells is that it does not have the protein cap located in eubacterial cells. Rather its flagellum is constructed by organizing small protein subunits. Something interesting that I came upon on is that the archaean flagellum is composed of many protein subunits.