how does KOH work on the cell membrane?
359728
Cell membranes are made of lipid bilayers, meaning it is made of a type of fat.  KOH is a strong base that is capable of reacting with the fat in the same reaction that produces soap.  This destroys the lipid bilayer
72954
The plasma membrane or the cell membrane is semi-permeable.Its function is to regulate the exchange of materials between the cytoplasm and extracellular fluid.
900729
No. The cell membranes are permeable to almost the same things, but specific carrier protein are needed for different functions, and this protein carriers are specific for some cell types.
468312
Potassium hydroxide is a strong base.\nKOH -> K+ + OH-\n\nWater doesn't participate directly in the reaction, so you can leave out the H2O on both sides. Because KOH is a strong base, it's pretty accurate to just have the arrow pointing one way in the reaction -- almost all of the KOH disassociates. For weak acids and bases, instead of an arrow pointing just in one direction, you need a bidirectional arrow to show that both sides of the equation are present in the solution. For example,\nH2CO3 <---> H+ + HCO3-
857859
mostly phospholipids (the bulk of the membrane is the phospholipid bilayer, with hydrophobic tails pointed towards each other and hydrophilic heads pointing out), with a bunch of proteins stuck in it like little potatoes :) \n\nmixed in the sea of phospholipids are small amounts of cholesterol (roughly the same size) to help prevent weakening of the cell membrane at high temperatures.\n\nAs for proteins, there are many types with many functions!\n- transport proteins\n- identity markers\n- junctioning proteins (stick to other cells)\n- anchors for cytoskeleton\n- enzymes\n- hormone receivers
273673
I'd have to say water (controls concentration gradients) and proteins (which form channels for things that can't cross the membrane by themselves).
612940
It would depend on several factors. Small, uncharged molecules can pass through the cell membrane through diffusion. When it is water, it is called osmosis. Diffusion can only occur into the cell when the concentration of the substance is greater outside the cell than within it, and likewise only out of the cell when the concetration is greater inside the cell than outside. This is called the concentration gradient.\n\nWhen the molecule is charged or is large (such as a chlorine ion or a lactose molecule), it requires active transport by carrier proteins. There are also carrier proteins that help to transport against the concentration gradient.\n\n[Edit] \nAfter thinking for a bit, I believe it would be pertinent to include something about the more complex methods of active transport.\n\nThere are two "directions" of the complex forms of active transport: in (endocytosis) and out (exocytosis).\n\nExocytosis is when a vesicle, after being released from the Golgi complex, fuses to the cell membrane, releasing the contents.\n\nEndocytosis is done by three main means: Phagocytosis, Pinocytosis, and Receptor-Mediated Endocytosis.\n\nPhagocytosis is the process of enveloping a large particle, such as how many unicellular organisms "eat" other organisms. The large particle comes in contact with the cell membrane, stimulating the formation of a vesicle. This vesicle then enters the cell and depending on the contents may fuse with a lysosome to help to digest it.\n\nPinocytosis also forms a vesicle, but differs from phagocytosis because it forms a much smaller vesicle.\n\nReceptor-mediated endocytosis is when particles that cannot normally enter the cell bond to receptor proteins embedded in the cell membrane. These proteins then congregate and form a vesicle. \n\nIn all forms of endocytosis and exocytosis, ATP is required for energy.
266097
Okay this is a bit of a complicated question, but i'll do my best, in short these are really very different things.\n\nFirst cell membranes are found in all cells (animal, plant, fungi etc.) they are made up of lipids, generally as a bilayer.  take the membrane from around the outside of a eukaryotic cell, its formed from phospolipids - these molecules have a hydrophilic head [ie will disolve in water/ has a charge] (the phosphate bit) and a hydrophobic tail (the lipid (fat) bit). The hydrophobic bits stick together and the hydrophilic bits are open to the solution on each side (search "lipid bilayer" with yahoo! Images if you want a diagram:-) ).  The outer cell membrane is forming a barrier between the inside and outside of the cell, alowing the cell to control the movment of molecules into and out of itself.  There are a lot of other membranes in the cell apart from the outher cell membrane, the endoplasmic reticulum for example is basicly made up of membrane.\n\nThe cell wall on the other hand isn't present in all cells (we humans (along with all other animals) don't get one). The cell wall is present on the extracellular side of the outer cell membrane.  it is hard and ridgid (unlike the membrane that is fluid) it is made up of lond polymers, and serves to protect the cell.  Plant cell walls are made up of mainly cellulose (in fact when you look at a peice of wood all you are really seeing is the leftover cell walls, and the rest of the cell has long gone).  Fungi also have cell walls but this time not made of cellulose but instead made of chitin, the cell wall still serves the same role however.\n\nIn short the membrane lets the cell control what goes in and out,  and the cell wall provides rigidity.  Membranes are made of lipids (fats) and cell walls of long polemers like chitin and cellulose.\n\nI hope this helps to answer your question, and look for some diagrams - it will make it a lot easier.
36291
alright i got this one for you right off the top of my head...\n\nfirst off i think you are talking about a receptor tyrosine kinase (RTK).  \n\nthings to know about an RTK: 1. a kinase is an enzyme that adds a phosphate to something else. 2. a receptor binds a ligand and leads to a signal activation.  3.  tyrosine is an amino acid that is found in the intracellular portion of a receptor tyrosine kinase.  4.  a membrane bound receptor is something that is encased inside the cell membrane. aka part of it is outside the cell and part of it is insdie the cell.\n\nso an RTK is a membrane bound receptor which receives an extracellular ligand and when the ligand binds the receptor a cross phosphorlyation event occurs in the intracellular portion of the receptor tyrosine kinase.  if you dont know what i'm talking about view the diagram below:\n\nextracellar space (outside of cell)\n+  <--Ligand aka extracellular signal\n&#92;/ <--- receptor portion of Receptor tyrosine kinase\n{}=====   <-- cell membrane  wraps around in a circle\n[]  <--kinase portion of receptor tyronsine kinase\nPxP <--- cross phosphorylation \n\n\nintracellular space (inside the cell)\n============ <-- more cell membrane that connects with the other cell memebrane\nextracellular space\n\n\nwhen the ligand (the + in the diagram) binds the receptor the cross phosphorylation occurs and then the signal proceeds via other chemical reactions into the nucleus where the DNA is housed.  \n\nWHY is this such a big deal?????  because this is the mechanism for how a cell is told to divide!  so basically when there is ligand present outside the cell and it hits the receptor then the cell divides.   the big point is that when the receptor does not work properly and the cross phosphorylation occurs IN THE ABSENCE of LIGAND then the tyrosine kinases is degregulated and this LEADS TO CANCER. \n\nwhy and how does it become deregulated and cross phosphorylate with out having to bind ligand?  mainly b/c the tyrosine kinase is defective when it is made by the cell.  This can happen because the DNA which is the blueprint or directions on how to make the tyrosine kinase is altered so that it shows the cell how to make a faulty or mutant tyrosine kinase.  Then it sticks this tyrosine kinase on the membrane but instead of waiting for ligand it just cross phosphorylates on its own and this leads to cancer.  \n\nI wrote sooo much i dont know if this helps.  but i doubt you will get a more complete answer to your question.  if you want a short quick answer. then it would be mutation in the DNA makes a bad tyrosine kinases which tells the cell to divide with out control.
103027
Alcohol is attracted to cell membranes, and it concentrates there. When it reaches nerve cell membranes, the alcohol can change the function of nerve cells and thus affect behavior.At one time, scientists believed that alcohol "dissolved" into the membrane interior and made the carbon chains of the lipids more fluid. (It was thought to be like converting hard butter into soft margarine.) \n\nWhen scientists tested this idea on fish, they realized that the "melted butter" idea could not explain intoxication. Warming fish by a few degrees can cause the same degree of lipid "melting", but t\nhe fish do NOT get intoxicated. The answer can be answered in part from the chemistry of alcohol (CH3CHOH). The carbon part of the molecule makes it attracted to the carbon tails of the lipids in cell membranes. But the OH group of alcohol makes it attracted to water. \n\nThus, you might expect that these influences would cause alcohol to orient itself in a membrane so that the carbon part of the molecule inserts itself into the membrane interior (where the lipid carbon tails are) and the OH part of the molecule is out near the surface, where the water is. This idea has been recently confirmed by the author of Cells Are Us and his colleagues here at Texas A&M.lcohol disrupts the normal organization of the lipid carbon chains (see picture below.)   \n\nYour scientist/author of this module believes that alcohol sticks to a membrane near its surface with water. Some of the evidence that supports this idea was obtained with a simple artificial lipid membrane. Several methods demonstrate that alcohol binds just underneath the charged head group of surface lipid, displacing some of the water that is normally there. The importance of this physical disruption is not so much what it does to the lipid, but what it does to the proteins (not shown) that are embedded in the lipid. Disturbing the shape of the lipids changes the shape of the proteins, and thus changes the functions of the protein.Think about how the substitution of alcohol for water might affect the large, complex sugars and proteins that are embedded in the lipid membrane. Ask yourself:\n\nWouldn't the substitution cause proteins to change shape? \n\nIf they changed shape, could that cause them to change function? \nAlthough the lipid of a membrane has no special function of its own, it does influence the large functional molecules (proteins and sugars) that the membrane contains. This is not a good thing.\n\nChanging a protein's shape or location can change the protein's function. Some membrane proteins are affected more by alcohol than are other proteins.
700313
NaOH + K+ = Na+ + KOH
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Assuming KOH is a strong base,\npOH = - log [-OH] = - log (1.00 M) = 0\npH + pOH = 14\npH = 14 - pOH\npH = 14\npH = - log [H+]\n[H+] = antilog(-pH)\n[H+] = 1 x 10^-14 M
791085
The cell membrane is a phospholipid bilayer, meaning there are two chains. Each chain has a serious of long non-polar tails (hydrophobic, hate water, non-permeable to polar molecules) with polar heads (hydrophilic, love water, permeable to polar molecules). The polar heads are on the outside of the membrane and the non-polar tails face the middle of the membrane. This structure prevents molecules from freely moving across the membrane. Embedded within the membrane are protein channels that are designed to specifically allow certain molecules through. Some of these channels open randomly, others require some kind of signal. They are selective by allowing molecules of certain size and/or charge (positive or negative) cross the membrane, also keeping in mind concentration gradients (molecules will move down their gradients). In some cases, molecules move against their gradients, but require energy to do it.
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Keep the cell contents bound together,exchange gases and excreta,Semi permeable entry i.e. it protects the cell by allowing only some Substances to enter the cell, maintains the shape of the cell and helps in transfer of water from cell wall as it has hydrophilic proteins in plants
730114
ok, so generally speaking, in the hypotonic environment, a cell is swell up, and potentially burst. The way to remember this is that hypO (the letter O)tonic is the cell which is normally drawn as a more squarelike shape becomes circular as it takes on water. In an isotonic solution, the environment and the cell have equal solutes so no movement of water occurs. In a hypertonic solution (lots of particles in the environment) so the water leaves the cell and shrivels up. \nHowever, we also have to take into account the type of cell that we are placing into these environments. The above applies to animal cells and paramecium as they don't have rigid cell walls. However, plant cells do have cell walls so it does not apply to them. Plant cells have what we call turgor pressor, so they can withstand the environmental influences, or changes in tonicity, alot better. When the plant takes on water, it has the cell wall to prevent bursting. When the plant cell looses water, the cytoplasm shrinks while the cell wall keeps the cell's shape.\n\nQuestion 2:\nIf you were to place elodea or paramecium from fresh to salt water:\nwhen elodea is placed in salt water, we observe the process of plasmolysis - shrinkage of cell contents due to water loss.\nfor image see:\nhttp://images.apple.com/education/solutions/iwork/lessons/media/RealWorldScienceSample.pdf\n\nWith Paramecium: it has 2 contratile vacuoles that are used to balance salt concentration by expelling water
771971
Cell membrane, or phospholipid bi-layer.
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Solutes that are too polar or highly charged to diffuse through the lipid bilayer and are too big to diffuse through membrane channels can cross the plasma membrane by facilated difussion.In this process, a solute binds to a specific transporter on one side of the membrane and is released on the other side after the transporter undergoes a changhe in shape.\n\nLike diffusion, facilitated diffusion is a passive process.The net result of facilitated diffusion is movement down a concentration gradient.The solute binds more often to the transporter on the side of the membrane with a higher concentration of solute.Once the concentration is the same on the both sides of the membrane,solute molecules bind to the transporter on the cystolic side and move out the extracellular side and move into the cytosol.The rate of facilitated diffusion(how quickly it occurs) is determined by the stepness of the concentration gradient across the membrane.\n\nThe number of transporters available in a plasma membrane places an upper limit,called the transport maximum,on the rate at which facilitated diffusion can occur.Once all the transporters are occupied, the transport maximum is reached, and further increase in the concentration gradient does not increase the rate of facilitated diffusion.Thus,much like a completely saturated sponge can absorb no more water,the process of facilitated diffusion exhibits saturation.\n\nHope this helps you.Please check my spelling too.I may misspelled some words.So many too typed.No time to check it.\n(^^o)/