Ch 8 Cell Membrane
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Created by:
eagleswings59 Plus on March 22, 2012
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Description:
Campbell
Classes:
BIOL 101, malonek ahs ap biology
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34 terms
Terms | Definitions |
|---|---|
 selectively permeable membrane | membrane that allows some substances to pass more easily than others and blocks the passage of some substances altogether |
| fluid mosaic model | The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids. |
| amphipathic | A molecule that has both a hydrophilic region and a hydrophobic region. |
| Davson and Danielli | proposed that cell membrane consists of a bilayer between 2 layers of protein |
| Singer and Nicolson | proposed that cell membrane consists of a fluid bilayer in which proteins are embedded (fluid-mosaic) in 1972 |
| integral proteins | Typically transmembrane proteins with hydrophobic regions that completely span the hydrophobic interior of the membrane. |
| peripheral proteins | Protein appendages loosely bound to the surface of the membrane and not embedded in the lipid bilayer. |
| transport proteins | A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane. |
| diffusion | the process by which molecules move from an area of higher concentration to an area of lower concentration |
| concentration gradient | a difference in the concentration of a substance across a distance |
| passive transport | The movement of materials through a cell membrane without using energy |
| osmosis | diffusion of water through a selectively permeable membrane |
| hypotonic | (of a solution) having a lower osmotic pressure than a comparison solution |
| hypertonic | (of a solution) having a higher osmotic pressure than a comparison solution |
| isotonic | of or involving muscular contraction in which tension is constant while length changes |
| osmoregulation | The control of water balance in organisms living in hypertonic, hypotonic, or terrestrial environments. |
| turgid | Firm. Walled cells become turgid as a result of the entry of water from a hypotonic environment. |
| flaccid | lacking firmness or stiffness when a cell has lost water |
| plasmolysis | the contraction or shrinking of the cell membrane of a plant cell in a hypertonic solution in response to the loss of water by osmosis |
| facilitated diffusion | movement of specific molecules across cell membranes through protein channels |
| aquaporins | a transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane |
| gated channels | A protein channel in a cell membrane that opens or closes in response to a particular stimulus. |
| sodium potassium pump | a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell |
| membrane potential | The charge difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions. Membrane potential affects the activity of excitable cells and the transmembrane movement of all charged substances. |
| electrochemical gradient | The diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to move relative to the membrane potential. |
| electrogenic pumps | special transport proteins that generate the voltage gradient across a membrane an example is the Na+-K+ pump restores the electrochemical gradient not only by the active transport of Na+ and K+ setting up a concentration gradient but because it pumps 2 K+ for every 3 Na+ setting up a voltage across membrane |
| proton pump | An active transport mechanism in cell membranes that uses ATP to force hydrogen ions out of a cell, generating a membrane potential in the process. |
| cotransport | The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient. |
| exocytosis | the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out |
| endocytosis | process by which a cell takes material into the cell by infolding of the cell membrane |
| phagocytosis | process in which extensions of cytoplasm surround and engulf large particles and take them into the cell |
| pinocytosis | process by which certain cells can engulf and incorporate droplets of fluid |
| receptor mediated endocytosis | The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances. |
| ligands | A molecule that binds specifically to a receptor site of another molecule. |
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