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46 Cards in this Set
- Front
- Back
fluid mosaic
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membrane structure, depicting a cellular membrane as a mosaic of diverse protein molecules embedded in a fluid bilayer made of phospholipid molecules
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selective permeability
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a property of biological membranes that allows some substances to cross more easily than others and blocks the passage of other substances altogether
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concentration gradient
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an increase or decrease in the density of a chemical substance in an area. Cells often maintain this across their membranes. When this exists, substances tend to move from where they are more concentrated to where they are less concentrated
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passive transport
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the diffusion of a substance across a biological membrane, without any input of energy
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diffusion
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the spontaneous tendency of a substance to move sown its concentration gradient from where it is more concentrated to where it is less concentrated
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osmosis
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the diffusion of water across a selectively permeable membrane
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tonicity
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the ability of a solution surrounding a cell to cause that cell to gain or lose water
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isotonic
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a solution having the same solute concentration as another solution, thus having no effect on passage of water in or out of the cell
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hypotonic
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in comparing two solutions, the one with the lower concentration of solutes; cells in such a solution will take up water from their surroundings
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hypertonic
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in comparing two solutions, the one with the greater concentration of solutes; cells in such a solution will lose water to their surroundings
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osmoregulation
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method by which organisms regulate solute concentrations and balance the gain and loss of water
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facilitated diffusion
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the passage of a subtance through a specific transport protein across a biological membrane down its concentration gradient
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aquaporins
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a transport protein in the plasma membrane of some plant or animal cells that facilitates the diffusion of water across the membrane
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active transport
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the movement of a substance across a biological membrane against its concentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP)
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exocytosis
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the movement of materials out of the cytoplasm of a cell by the fusion of vesicles with the plasma membrane
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endocytosis
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cellular uptake of molecules or particles via formation of new vesicles from the plasma membrane
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phagocytosis
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cellular "eating"; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm
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pinocytosis
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cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolves solutes into small membranous vesicles
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receptor-mediated endocytosis
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the movement of specific molecules into a cell by the inward budding of membranous vesicles. The vesicles contain proteins with receptor sites specific to the molecules being taken in
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energy
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the capacity to perform work, or to rearrange matter
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kinetic energy
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the energy of motion; the energy of a mass of matter that is moving. Moving matter does work by imparting motion to other matter
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heat
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thermal energy; the amount of energy associated with the movement of the atoms and molecules in a body of matter. Energy in its most random form
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potential energy
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the energy that matter possess because of its location or arrangement.
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chemical energy
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energy available in molecules for release in a chemical reaction
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thermodynamics
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the study of energy transformation that occurs in a collection of matter
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first law of thermodynamics
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the principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed
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entropy
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a measure of disorder
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second law of thermodynamics
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the principle whereby every energy conversion reduces the order of the universe, increasing its entropy. Ordered forms of energy are at least partly converted to heat
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exergonic reaction
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an energy-releasing chemical reaction in which the reactants contain more potential energy than the products. The reaction releases an amount of energy equal to the difference in potential energy between the reactants and the products
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cellular respiration
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the aerobic harvesting of energy from food molecules; the energy-releasing chemical breakdown of food molecules, such as glucose, and the storage of potential energy in a form that cells can use to perform work; involved glycolysis, the citric acid cycle, and oxidative phosphorylation (the electron transport chain and chemiosmosis)
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endergonic reactions
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an energy-requiring chemical reaction, which yields products with more potential energy than the reactants. The amount of energy stored in the products equals the difference between the potential energy in the reactants and that in the products
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metabolism
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the totality of an organism's chemical reactions
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metabolic pathway
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a series of chemical reactions that either builds or breaks down a complex molecule into simpler compounds
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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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ATP
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a cluster of several membrane proteins that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion concentrations gradient
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phosphorylation
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the transfer of a phosphate group, usually from ATP, to a molecule. Nearly all cellular work depends on ATP energizing other molecules using this process
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energy of activation
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the amount of energy that reactants must absorb before a chemical reaction will start
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enzymes
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a protein that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process
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substrate
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a specific substance on which an enzyme acts. Each enzymes recognizes only the specific one of the reaction it catalyzes.
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active site
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the part of an enzyme molecule where a substrate molecule attaches (by means of weak chemical bonds); typically, a pocket or groove on the enzyme's surface
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induced fit
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the change in shape of the active site of an enzyme, induced by entry of the substrate so that it binds more snugly to the substrate
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cofactors
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a nonprotein molecule or ion that is required for the proper functioning of an enzyme
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coenzyme
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an organic molecule serving as cofactor
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competitive inhibitor
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a substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate. It mimics that of the enzyme's substrate.
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noncompetitive inhibitor
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a substance that impedes the activity of an enzyme without entering an active site. By binding elsewhere on the enzyme, it changes the shape of the enzyme so that the active site no longer functions
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feedback inhibition
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a method of metabolic control in which a product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway
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