Chapter 7
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MelSell2011 on September 27, 2010
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Membrane Structure and Func
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49 terms
Terms | Definitions |
|---|---|
 cell membrane | a plasma phospholipid bilayer controlling traffic into and out of the cell |
| selectively permeable | allowing some substances to cross the membrane more easily than others |
| lipids and proteins | staple ingredients of a membranes |
| amphipathic molecule | a phospholipid having a hydrophilic and hydrophobic region |
| fluid mosaic model | currently accepted model of a cell membrane structure. Envisions it as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids. |
| cholesterol | temperature buffer |
| integral proteins | penetrate the hydrophobic core of the lipid bilayer |
| transmembrane proteins | span the entire membrane, going through all layers of the cell membrane. |
| peripheral proteins | not embedded into the lipid bilayer AT ALL, appendages loosely bound to the surface of the membrane, often exposed to parts of the integral proteins. |
| transport, enyzmatic activity, signal transduction, cell to cell recognition, intercellular joining, attachment to cytoskeleton | 6 major functions performed by proteins |
| transport | a.) proteins that span the membrane can provide hydrophilic channel across the membrane. b.) others shuttle a substance from one side to the other by changing shape ex: hydrolyzing ATP as an energy to actively transport substances across the membrane. |
| enzymatic activity | a protein built into the membrane may be an enzyme with its active site exposed to substances in the adjacent solution. also organize as a team to carry out metabolic pathways. |
| signal transduction | membrane protein called a receptor may have a binding site with a specific shape that fits the shape of a chemical messenger, such as a hormone. The signaling molecule may cause a shape change. |
| cell to cell recognition | some glycoproteins serve as identification tags that are specifically recognized by membrane proteins of other cells. distinguish one type of neighboring cell from another. basis for rejection of foreign cells. |
| intercellular joining | membrane proteins of adjacent cells may hook together in various kinds of junction, i.e. gap junctions or tight junctions. |
| attachment to cytoskeleton | microfilaments or other elements of the cytoskeleton may be noncovalantly bound to membrane proteins, this helps maintain cell shape and stabalizes the location of certain membrane protens. *Proteins that bind to Extra Cellular Membrane molecules can coordinate extracellular and intracellular change. |
| glycolipids | a lipid with a covalently attached carbohydrates., membrane carbohydrates that are covalently bonded to lipids |
| glycoproteins | a protein with one or more carbohydrate covalently attached to it. distinguish one cell from another. |
| transport proteins | transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane, lipid bilayer acts as gate keeper. |
| channel proteins | function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel thru the membrane |
| aquaporins | channel protein in plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of water across the membrane. |
| carrier proteins | transport proteins that hold onto their passengers and change shape in a way that shuttles them across the membrane |
| thermal motion | molecules posses an energy called this, which results in diffusion |
| diffusion | result of thermal motion, the movement of molecules of any substance so that they spread out evenly in the available space. |
| concentration gradient | the region along which the density of a chemical substance decreases |
| passive transport | the diffusion of a substance across a biological membrane. The cell does not ave to use energy to make it happen |
| osmosis | the diffusion of water across a selectively permeable membrane, balance of water between cell and environment |
| tonicity | the ability of a solution to cause a cell to gain or lose water |
| isotonic | a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell, stableness |
| hypertonic | a solution that, when surrounding a cell, will cause the cell to lose water, causing a cell to die. |
| hypotonic | a solution that, when surrounding a cell, will cause the cell to take up water. water enters faster than it leaves causing the cell to burst |
| osmo regulation | control of water balance |
| turgid | very firm cell in plants |
| flaccid | limp cell in plants |
| plasmolysis | the cytoplasm shrivels and the plasma membrane pulls away from the cell walls, when cell loses water to a hypertonic environment. |
| facilitated diffusion | diffusion of molecules across the lipid bilayer with help from proteins |
| ion channels | funciton as gated channels which open or close in response to a stimulus |
| active transport | movement of a substance across a cell membrane, with an expenditure of energy. to pump and solute across a membrane against its gradient requires work! |
| sodium-potassium pump | 1. transport protein in plasma membrane that actively transports sodium out of the cell and potassium in. |
| membrane potential | voltage difference across cell membrane, inside is neg and outside is positive. |
| electrochemical gradient | combinations of forces acting on an ion |
| electrogenic pump | 2. transport protein that generates voltage across a membrane |
| cotransport | 3. occurs when active transport of a solute indirectly drives the transport of another solute ex: active transport out and passive transport in |
| exocytosis | 4. cell secretes certain biological molecules by the fusion of vesicles with the plasma membrane, removing from the cell |
| endocytosis | 5. cell takes in biological molecules to form new vesicles from the plasma membrane. |
| phagocytosis | cellular eating of solids |
| pinocytosis | cellular drinking of liquids |
| receptor-mediated | enables cell to acquire bulk quantities of specific substances, even though those substance may not be very concentrated |
| ligands | any molecule that binds specifically to a receptor site of another molecule |
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