Ch. 8 Membrane Structure and Function
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sagenorrie on August 31, 2011
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118 terms
Terms | Definitions |
|---|---|
 Energy | The ability to do work, free energy/ total energy. |
| Metabolism vs. Combustion | Sum of total of all chemical reactions. |
| First Law of Thermodynamics | Energy can neither be created or destroyed. |
| Second Law of Thermodynamics | Low quality of energy is increasing. |
| Entropy | The measure of disorder. |
| Potential energy | Energy of position. |
| Kinetic energy | Energy of motion. |
| Exergonic | Chemical reactions tha show a net loss of energy. ATP > ADP + Pi |
| Endergonic | Chemical reactions that show a net gain in energy. ATP + Pi > ATP |
| Colchicine | Inhibits the process of mitosis. |
| Cholinesterase Inhib. | Inhibits the action of cholinesterase in nerve impulses. |
| Cholesterol inhib. | Suppresses the production of cholesterol or decresases the level of cholesterol or decreases the level of cholesterol in the blood. |
| Lysine/Theronine | Prevents growth of gemmae in liverworts. |
| Enzymes | Speed up the tate of reaction by decreasing the free energy of activation |
| The plasma membrane separates | The living cell from its surroundings. |
| Plasma membrane measures | 8nm. |
| Selective permeability | Allows some substances to cross it more easily than others. |
| Staple ingredients of membranes | Lipids and proteins. |
| Amphipathic | A molecule that has both a hydrophilic region nd hydrophobic region. |
| Fluid mosaic model | The currently accepted model of cell membrane structures, which envisions the membrane as a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids. |
| Garter an Grendel | Dutch scientists who reasoned that cell membranes must be phospholipid bilayers. |
| Hugh Dawson and Danielli | Proposed a sandwich model: a phospholipid bilayer between two layers of proteins. |
| Freeze fracture | A method of preparing cells for electron microscopy that demonstrated visually that proteins are embedded in the phospholipid bilayer of membrane. |
| A membrane is held together by | Hydrophobic interactions. |
| Adjacent phospholipids | Switch positions 10^7 times oer second. |
| A membrane remains fluid as temperature | Decreases until finally the phospholipids settle into a closely packed arrangement andthe membrane solidifies. |
| Termperature a membrne solidifies at depends on | The type of lipids it is made of. |
| At relatively higher temperature, cholesterol | Makes the membrane less fluid by restraining phospholipid movement. |
| Because cholesterol hinders close packing of phospholipids | It lowers the termperature required for the membrane to solidify. |
| Cholesterol can be | Thought of as a termperature buffer for the membrane, resisting changes in membrane fluidity that can be caused by changes in termperature. |
| Membranes must be | Fluid to work properly. When membrane solidifies, its permeability changes, and enzymatic protein in the membrane may become inactive. |
| Lipid composition may change as an | Adjustment to changing temperature. |
| A membrane is a collage of | Different proteins embedded in the fluid matrix of the lipid bilayer. |
| More than 50 kinds of | Proteins have been found so far in the plasma membranes of red blood cells. |
| Proteins determine most of | The membrane's functions. |
| Integral proteins | Penetrate the hydrophobic core of the lipid bilayer. Many are trans-membrane proteins, which span the membrane; other integral proteins extend only partway into the hydrophobic core. |
| Te hydrophobic regions of an integral protein consist of | One or more stretches of nonpolar amino acids, usually coiled into a(fish thing) helixes. |
| Peripheral proteins | Are not embedded in the lipid layer at all; they are appendges loosely bound to the surface of the membrane, often exposed parts of integral proteins. |
| Cell-cell recognition | A cell's ability to distinguish one type of neighboring cell from another, is crucial to the functioning of an organism. |
| Cell-cell recognition is important in | The sorting of cells into tissuesand organs in animal embryo. Also rejects foreign cells by the immune system. |
| Cells recognize otherclls by | Binding to surface mlecus, often to carbohydrate, on the plasma of the membrane. |
| Membrae carbohydrates are | Usually shot, branched chains of fewer than 15 sugar units. |
| Gycolipids | A lipid with covalently attached carbohydrate |
| Glycoprotein | A protein with one or more carbohydrate covalently attached to it. |
| The carbohdrates on extracellular side of plasma membrane | Vary from species among individuals and even from cell to cell in a person. |
| The 4 human blood types A, C, AB, and O reflect | Variation in the carbohdrates on the surface of red blood cells. |
| When vesicle fuses with plasma membrane | The outside layer of the vesicle becomes continuous with the cytoplasmic (inner) layer of the plasma membrane. Therefore molecules that start out on the inside face of the ER end up on the outside face of the plasma membrane. |
| Process of vesicle fusion | Synthesis of membrane protein and lipids in the endoplasmic reticulum. Carbohydrates are added to the proteins, making them glycoproteins. |
| 2nd step of vesicle fusion | Inside the Golgi apparatus the glycoproteins undergo further carbohydrate modification, and lipids acquire carbohydrates becoming glycolipids. |
| 3rd step of vesicle fusion | The transmembrane proteins, glyco lipids, and secretory proteins are transported to plasma membrane. |
| 4th step of fusion | The vesicles fuse with the membrane, releasing secretory proteins from the cell. |
| Vesicle fusion positions the carbohydrates | Of membrane glycoproteins and glycolipids on the outside of the plasma membrane. |
| The cell regulates its concentrations by | Shuttling them one way or the other across the plasma membrane. |
| Cell membranes are | Selectively permeable and substance do not pass indiscrimminately. |
| Nonpola molecules like hydrocarbons, CO2, and oxygen | Are hydrophobic and can therefore dissolve in the lipid bilayer of the membrane and cross it easily without the aid of membrane proteins. |
| Polar molecules such as glucose and sugars | Pass only slowly through a lipid bilayer, and even water, an extremely small polar molecule, does not cross very rapidly. |
| A charged atom or olecule surrounding shellof watr | Find the hydrophobic layer of the membrane even more difficult to penetrate. |
| Transport Proteins | A transmembrane protein that helps a certain substance or class of closely related substances to cross the membane. |
| Cell membranes are permeable to | Specific ions an variety of polar molecules. |
| Channel proteins | Function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane. |
| Aquaporins | A channel protein in the plasma of a plant, animal, or microorganism cell that specifically facilitated osmosis, the diffusion of water across the membrane. |
| Aquaporins allows | Entry of up to 3 billion water molecules per second, passing single file through its central channel, which fits 10 at a time. Bring temendous increase in rate. |
| carrier proteins | Transport protein that holds its passengers and change shape in a way that shuttles them across the membrane. |
| A transport protein is | Specific for the substance it translocates (moves), allowing only a certain substance (or substances) to cross the membrane. |
| Diffusion | The movement of molecular of any substance so that they spread out evenly into the available space. Is result of thermal motion. |
| Thermal motion | Heat |
| Concentration gradient | A region along which the density of a chemical substance increases or decreases. |
| Diffusion is a | Spontaneous process needing no input of energy. |
| Passive transport | The diffusion of a substance across a biological membrane with no expenditure of energy. |
| The concentration gradient represents | Potential energy and drives diffusion. |
| Water diffuses across membrane from the | Region of lowe solte concentration until the solute on both sides of the membrane are equal. |
| Osmosis | The diffusion of water across a selectively permeable membrane. |
| Tonicity | The ability of a solution to cause a cell to gain or lose water. |
| Isotonic | Referring to a solution that, when surrounding a cell, has no effect on the passage of water into or out of the cell. |
| Hypertonic | Referring to a solution, that well surrounding a cell, will cause the cell lose water. Cell will shrivel, probably die. |
| Hypotonic | Referring to a solution that, when surrounding cell, will cause cell to take up water. Cell wil swell and lyse (burst). |
| Osmoregulation | The control of water balance. |
| Paramecium | Lives in pond water, which is hypotonic to the cell. It has a plasma membrane that isn't very permeable to water but that will only slow the uptake od water, which continually enters the cell. |
| Why doesn't Paramecium burst? | It is equipped with a contractile vacuole, an orgaelle that functions as a bilge pump to force water out of the cell as fast as it enters by osmosis. |
| The cells of plants, prokaryotes and some protists | All have walls. |
| When a cell with a wall is placed in a hypotonic solution | The wall helps maintain the cell's water balance. |
| Turgid | Swollen, which is healthy for plant cells. |
| Non-woody plants (like house plants) | Depend on cell kept turgid by a surrounding hypotonic solution, for mechanical support. |
| If plants cells surroundings are isotonic | There is not net tendency for water to enter and cells become flaccid. |
| Flaccid | Limp |
| Plasmolysis | A phenomenon in walled cells in which the sytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when cell loses water to a hypotonic environment. |
| Facilitated diffusion | The spontaneous passage of molecules or ions across a biological membane with the assistance of specific transmembrane transport proteins. |
| Ion channels | A transmembrane protein channel that allows a specific ion to flow accros the membrane down its concentration gradient. |
| Gated channels | A transmembrane protein channel that opens or closes in response to a particulat stimulus. Stimulus is electrical or chemical. |
| In cystinuria | A carrier protein that transports cystein and some other amino acids across the membranes of kidney cells is absent. Kidney cells normally reabsorb these amino acids from urine and return them to the blood but individual gets painful stones from amino acids that accumulate and crystallize in the kidneys. |
| Facilitated diffusion is considered passive transport because | The solute is moving down its concentration gradient. |
| To pump solute across membrane against its gradient | Requires work; the cell must expend energy. |
| Active transport | The movement of substnce across a cell membrnce with an expenditure of energy, against its concentration gradient; mediated by specific transport proteins. |
| Compared to its surrouding, animal cell has | Much higher concentration of potassium ions and a much lower concentration of sodium ions. |
| The plasma membrane heps maintin these steep gradients by | Pumping sodium out of the cell and potassium into the cell. |
| ATP | Supplies the energy for most active tansport by transferring its terminal phosphate group directly to the transport protein. |
| Sodium-potassium pump | Exchanges sodium (Na+) for potassium (K+) across the membrane of animal cells. |
| Voltage | Electrical potential energy. A separation of opposite charges. |
| The cytoplasm is | Negative in charge relative to extracellular fluid because of an unequal distributin of anions and cations on opposite sides of the membrane. |
| Membrane potential | The voltage across a membrane, which ranges from about -50 to -200 millivolts. |
| Membrane potential favor the | Passive transport of cations into the cell and anions outside of the cell. |
| Electrochemical gradient | The diffusion gradient of an ion, which is affected by both the concentration difference of the ion across the membrane (chemical force) and the ion's tendency to move relative to the membrane potential (electrical force). |
| Ion diffuses not simply down its concentration gradient but | Down its electrochemical gradient. |
| The sodium-potassium pum | Pumps the sodium ions out of three cell for every two potassium ions it pumps into the cell. |
| Electrogenic pump | An ion transport protein that generates voltage across a membrane. |
| Proton pump | Main electrogenic pump of plants, fungi, and bacteria, which actively transports hydrogen ions (H+) out of the cell. |
| The pumping of H+ | Transfers positive charge from the cytoplasm to the extracellular solution. |
| An important use of proton gradients in cell is | The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient. |
| Plants use sucrose H+ cotransport to | Load sucrose produced by photosynthesis into cells in veins and leaves. |
| exocytosis | The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane. |
| Many secretory cells use exocytosis to | Export products. |
| Endocytosis | Cellular uptake of biological molecules and particulate matter via formation of new vesicles from the plasma membrane. |
| Three types of endocytosis | Photosynthesis, pinocytosis, and receptor-mediated endocytosis. |
| Phagocytosis | A type of endocytosis in which large particulate substances are taken up by the cell. Carried out by certain immune cells and protists in animals. |
| Pinocytosis | A type of endocytosis in which the cell ingests extracellular fluid and its dissolved fluids. |
| 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 | Any molecule that binds specifically to a receptor site of another molecule |
| Human cells use receptor-mediated endocytosis to | Take in cholesterol for the use in the synthesis of membranes and other steroids. |
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