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61 Cards in this Set
- Front
- Back
What is a fluid mosaic?
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description of a membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded ina fluid bilayer of phsopholipid molecules.
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What is selective permeability?
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property of biological membranes that allows some substances to cross more easily than other and blocks the passage of other substances altogether.
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What is diffusion?
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spontaneous movement of a substance down its concentration gradient from where it is more concentrated to where it is less concentrated.
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What is concentration gradient?
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- region along which the density of a chemical substance increases or decreases.
- cells often maintain one made of ions across their membranes - when it exists, substacnes tend to move from where they are more concentrated to where they are less concentrated. |
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What is passive transport?
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the diffusion of a substance across a biological membrane with no expenditure of energy.
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the cell doesn't expend energy to transport substance that are diffusing down their concentration gradient.
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Why is diffusion across a membrane called passive transport?
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What is osmosis?
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diffusion of water across a selectively permeable membrane.
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What is tonicity?
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- ability of a solution surrounding a cell to cause that cell to gain or lose water
- mainly depends on its concentration of solutes that can't cross the plasma membrane relative tot he concentration of solutes inside the cell. |
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What is isotonic mean?
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- referring to a solution that, when surrounding a cell, has no effect on the passage of water in or out of the cell.
- equal solute concentration |
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What does hypotonic mean?
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referring to a solution that, when surrounding a cell, will cause the cell to gain water.
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What does hypertonic mean?
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referring to a solution that, when surrounding a cell, will cause the cell to lose water
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What is osmoregulation?
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homeostatic maintenance of solute concentrations and the balance of water gain and loss
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What is facilitated diffusion?
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- passage of a substance through a specific transport protein across a biological membrane down its concentration gradient
- type of passive transport |
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What is aquaporin?
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transport protein in the plasma membrane of some plant or animal cell that facilitates the diffusion of water across the membrane.
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because they are specific for the solutes they transpor, the numbers and kinds of transport proteins affect a membrane's permeability to various solutes.
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How do transport proteins contribute to a membrane's selective permeability?
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kidney cells must reabsorb a large a mount of water when producing urine.
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What are aquaporins important in kidney cells?
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What is active transport?
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movement of a substance across a biological membrane against its concentration gradient, aidded by specific transport proteins and requring an input of energy.
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What is exocytosis?
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movement of materials out of the cytoplasms of a cell by the fusion of vesicles with the plasma membrane.
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What is endocytosis?
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cellular uptakeof molecules or particle via formation of new vesicles from the plasma membrane.
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What is phagocytosis?
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- cellular eating
- type of endocytosis in which a cell engulfs macromolecules, other cells, or particles into its cytoplasm |
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What is pinocytosis?
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- cellular drinking
- type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles. |
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What What is receptor-mediated endocytosis?
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- movement of specific molecules into a cell by the inward budding of membranous vesicles
=contains proteins with receptor sites specific to the molecules being taken in |
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- exocytosis; when a transport vesicles fuses with the plasma membrane, its contnets are released and the vesicle membrane adds to the plasma membrane
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As a cell grows, its plasma membrane expands. Does this involove endo/exo cytosis? Explain.
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What is energy?
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capacity to cause change, especially to perfrom work.
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What is kinetic energy?
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- energy of motion; energy of a mass of matter that is moving
- moving matter does work by imparting motion to other matter |
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What is potential energy?
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- the energy that matter posesses because of its location or arrangement
- EX: water behind a dam; chemical bonds |
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What are thermodynamics?
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study of energy transformation that occurs in a collection of matter
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What is the first law of thermodynamics?
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- principle conservation of energy
- can be transferred and transformed, but it can't be created or destroyed |
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What is the second law of thermodynamics?
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- principle stating that every energy conversion reduces the order of the niverse, increasing its entropy
- ordered forms of energy, are at least partly converted to heat |
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What is chemical energy?
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- energy available in molecules for release in a chemical reaction
- form of potential energy |
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What is cellular respiration?
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- aerobic harvesting of energy from food molecules
- energy-releasing chemical breakdown of food molecules, such as gluecose, and the storage of potential energy in a form that cells can use to perform work - involves; glycolosis, citric acid cycle, and oxidative phosphorylation (electron transport chain and chemiosmosis) |
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What is entropy?
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- measure of disorder
EX: heat, which is random molecular motion |
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diffusion across a membrane results in equal concentrations of solutes, which is a more disorded arrangement (higher entropy) than a high concentration on 1 side and a low concentration on the other
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How does the 2nd law of thermodynamics explain the diffusion of a solute across a membrane?
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What is an exergonic reaction?
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- an energy-releasing chemical reaction in which the reactants contain more potential energy than the products
- reaction releases an amount of enrgy equal to the difference in potential energy between the reactants and products |
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What is an endergonic reaction?
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- energy requiring chemical reaction, which yields products with more potential energy than the reactants
- amount of energy stored in the products equal the difference between the potential energy in the reactants and that in the products |
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What is metabolism?
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totality of an organism's chemical reaction
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What is metabolic pathway?
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series of chemical reaction that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
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What is energy coupling?
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in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.
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some of it is stored in ATP molecules; the rest is releasaed as heat.
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What becomes of the energy extracted from food during cellular respiration?
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What is ATP?
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- powers nearly all forms of cellular work
- adenosine triphosphate |
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What is phosporylation?
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- transfer of phosphate group, usuall from ATP, to a molecule
- nearly all cellular work depends on ATP energizing other molecules by phosphorylation. |
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What are the 3 types of cellular work?
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- chemical
- mechanical - transport |
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Describe chemical cellular work.
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- phosphorylation of reactants provides energy to drive the endergonic synthesis of products.
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Describe mechanical cellular work.
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- transfer of phosphate groups to special motor proteins in muscle cells cause the proteins to change shape and pull on protein filaments, in turn causing the cells to contract
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Describe transport cellular work.
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- ATP drives the active transport of solutes across a membrane against their concentration gradient by phosphorylating transport proteins
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ATP is a renewable resource
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Why can work be sustained?
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exergonic processes phosphorylate ADP to form ATP, ATP transfers energy to energonic processes by phosphorylating other molecules
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How does ATP transfer energy from exergonic to endergonic processes in the cell?
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What is activation energy?
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- amount of energy that reactants must absorb before a chemical reaction will start
- protects the highly ordered molecules of your cells from spontaneously breaking down |
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What are enzymes?
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- macromolecule, usually a protein, that serves as a biological catalyst, change the rate of a chemical reaction without being consumed by the reaction
- speeds up reaction by lowering the activation energy needed for the reaction to begin |
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What are substrates?
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- specific substance on which an enzyme acts. Each enzyme recgonizes only the specific substrate or substrates of the reaction it catalyzes
- surface in or on which an organism lives |
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What is an active site?
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part of an enzyme molecule where a substrate molecules attaches ( by means of weak chemical bonds); typically a pocket or groove on the enzyme's surface
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What is the catalytic cycle?
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1. enzyme starts with empty active site
2. sucrose eneters the active site, attaching by weak bonds - active site changes shape slightly 3. substate is converted to products; glucose and fructose 4. products are released |
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What are induced fits?
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change in shape of the active site of an enzyme, caused by entry of the substrate, so that it binds more snugly to the substrate
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What are cofactors?
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- nonprotein molecule or ion that is required for the proper function of an enzyme
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Whaat is a coenzyme?
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- organic cofactor
- most vitamins function as these in important metabolic reaction |
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- enzyme lowers the activation energy needed for a reaction when its specific substrate eneters its activation site
- with an induced fit, enzyme strains bonds that need to break or positions substates in an orientation that aids the conversion of reactants to products |
How do enzymes speed up a specific reaction?
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What is a competitive inhibitor?
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- substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate
- structure mimics that of the enzyme substrate |
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What is a noncompetitive inhibitor?
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- substance that decreases the activity of an enzyme without entering an active site
- by binding elsewhere on the enzyme it changes the shape of an enzyme so that the active site no longer effectively catalyzes the conversion of substrate to a product |
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What is a feedback inhibition?
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method of metabolic control in which a product of a metabolic pathaway acts as an inhibitor of an enzyme within that pathway
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- prevents the cell from wasting valuable resources by synthesizing more of a particular product than is needed
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What is advantage of feedback inhibition to a cell?
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- if the inhibitor binds to the enzyme with covalent bonds, the inhibition is usually irreversible.
- when weak chemical interaction bind inhibitor and enzyme, the inhibition is reversible. |
What determines whether enzyme inhibition is reversible or irreversible?
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