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23 Cards in this Set
- Front
- Back
energy
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the capacity to bring about movement against an opposing force
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potential energy
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stored energy: the rock perched precariously at the top of the hill; the charged ions kept on one side of a cell membrane
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kinetic energy
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energy in motion, as with the rock tumbling down the hill or charged ions rushing in through a protein channel
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thermodynamics
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the study of energy
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first law of thermodynamics
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energy is never created or destroyed
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second law of themodynamics
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energy transfer always results in a greater amount of disorder in the universe
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energy transformed
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in a steam engine, energy locked up in the chemical bonds of coal is transformed into heat energy and mechanical energy. No energy is lost in this process, but energy is transformed from a more ordered form (the chemical bonds of coal) to a less ordered form (heat). Thus, the amount of disorder-or entropy-increases in the transaction.
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exergonic reactions
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reactions in which the starting set of molecules (the reactants) contains more energy than the final set of molecules (the products)
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endergonic reactions
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reactions in which the products contain more energy than the reactants.
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energy stored and released
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it takes energy to build up a more complex molecule (in this case, glycogen) from simpler molecules (in this case, glucose units). such a buildup is thus an endergonic or uphill reaction. conversely, energy is released in reactions in which more complex molecules are broken down into simpler ones. such reactions are exergonic or downhill reactions
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coupled reaction
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chemical reaction in which an exergonic reaction powers an endergonic reaction
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ATP (adenosine triphosphate)
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ATP stores energy in the form of chemical bonds between phosphate groups. When the bond between the second and outermost phosphate group is broken, the outermost phosphate separates from ATP, and energy is released. This separation transforms ATP into ADP, which then goes on to pick up another phosphate group, becoming ATP again.
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enzyme
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a type of protein that accelerates a chemical reaction
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substrate
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a substance whose chemical alteration is facilitated by an enzyme
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matabolic pathway
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a sequential set of enzymatically controlled chemical reactions in which the product of one reaction serves as the substrate for the next
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metabolism
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the sum of all chemical reactions carried out by a cell or larger organism
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activation energy
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the energy required to initiate a chemical reaction. Enzymes lower the activation energy of a reaction, thereby greatly speeding up the rate of the reaction
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catalysts
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a substance that retains its original chemical composition while bringing about a change in a substrate. enzymes are catalysts in chemical reactions; one enzyme can carry out hundreds or thousands of chemical transformations without itself being transformed.
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active site
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the portion of an enzyme that binds with a substrate, thus helping transform it
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co-enzymes
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a type of accessory molecule that binds to the active site of an enzyme, thus allowing the enzyme to bind to its substrate. many vitamins are coenzymes
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competitive inhibition
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a reduction in the activity of an enzyme by means of a compound other than the enzyme's usual substrate binding with it in its active site
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allosteric regulation
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the regulation of an enzyme's activity by means of a molecule binding to a site on the enzyme other than its active site
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enzyme chymotrypsin
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the enzyme chymotrypsin is facilitating the breakdown of a protein by changing the protein's shape. in the absence of chymotrypsin, the process wold take a billion times longer
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