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34 Cards in this Set
- Front
- Back
Metabolism
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the totality of an organism’s chemical processes; an emergent property of life that arises from specific interactions between molecules within the orderly environment of the cell
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Catabolic pathways
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Degradative processes in which complex molecules are broken down into simpler molecules; one major component of catabolism is cellular respiration, in which sugar glucose is broken down into carbon dioxide and water
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Anabolic pathways
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Processes that consume energy to build complicated molecules from simpler ones (e.g. synthesis of proteins from amino acids)
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Energy coupling
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the transfer of energy from catabolism to anabolism;
energy that is produced through catabolic processes (downhill) is used to drive anabolic processes (uphill) |
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Bioenergetics
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the study of how organisms manage their energy resources
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Energy
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the capacity to do work; the ability to rearrange a collection of matter
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Kinetic Energy
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the energy of motion
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Potential Energy
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the energy that matter possesses because of its location or structure
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Chemical Energy
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a form of potential energy; stored in molecules because of the structural arrangement of the atoms in those molecules
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Thermodynamics
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the study of energy transformation that occur in a collection of matter
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First law of thermodynamics
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states that the energy of the universe is constant; energy can be transferred and transformed, but it can be neither created nor destroyed
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Second law of thermodynamics
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every energy transfer or transformation increases the entropy (disorderliness) of the universe; an organism takes in organized forms of matter and energy from the surroundings and replaces them with less ordered forms; when a spontaneous process occurs in a system, the stability of that system increases (e.g. when water flows downhill, its system increases in stability)
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Free energy
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the portion of a system’s energy that can perform work when temperature is uniform throughout the system; free energy (G) = the system’s total energy (H) – temperature Kelvin (T) x entropy (S)
G=H-TS |
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Exergonic Reation
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a reaction that proceeds with a net release of free energy; spontaneous reactions
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Endergonic Reaction
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a reaction that absorbs free energy from the surroundings; nonspontaneous reactions
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Energy coupling
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the use of an exergonic process to drive an endergonic process
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ATP (Adenosine triphosphate)
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molecule used to power cellular processes; closely related to one type of nucleotide found in nucleic acids; bonds between phosphate groups can be broken by hydrolysis to yield energy and ADP (adenosine diphosphate)
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Phosphorylated intermediate
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through the help of enzymes, the free phosphate ion from ATP is transferred to another molecule within the cell; this avoids loss of the free energy and is the key to energy coupling within the cell; this intermediate is more reactive than the original molecule
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Enzymes
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catalytic proteins
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Catalyst
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a chemical agent that changes the rate of a reaction without being consumed by the reaction
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Activation energy
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the energy required to break the bonds in the reactant molecules; initial investment of energy for starting a reaction
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Substrate
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the reactant an enzyme acts on
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Active site
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typically a pocket or groove on the surface of the protein; a limited region of the enzyme that actually binds to the substrate; usually formed by only a few of the enzyme’s amino acids, with the rest of the protein molecule providing a framework that reinforces the configuration of the active site
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Induced fit
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an induced change in the conformation of the enzyme that allows it to bind more snuggly to the substrate; brings chemical groups of the active site into positions that enhance their ability to catalyze the chemical reaction
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Cofactors
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nonprotein helpers required by some enzymes for catalytic activity; may be bound tightly to the active site as permanent residents, or they may bind loosely and reversibly along with the substrate; some of these are inorganic compounds
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Coenzyme
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organic cofactors are more specifically called coenzymes
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Competitive inhibitors
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inhibitors that closely resemble the normal substrate molecule and compete for admission into the active site; reduce the productivity of enzymes by blocking the substrate from entering active sites; this is reversible by increasing the amount of substrate
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Noncompetitive inhibitors
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inhibitors that do not directly compete with normal substrate at the active site; impede enzymatic reactions by binding to another part of the enzyme; causes enzyme to change its conformation, rendering the active site unreceptive to substrate or leaving the enzyme less effective at catalyzing the conversion of substrate to product
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Allosteric site
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a site remote to the active site where regulatory molecules can bind to an enzyme and change its shape and function
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Feedback inhibition
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the switching off of a metabolic pathway by its end-product, which acts as an inhibitor of an enzyme within the pathway
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Cooperativity
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if an enzyme has two or more subunits, this interaction with one substrate molecule triggers the same favorable conformational change in all other subunits of the enzyme; amplifies the response of enzymes to substrates
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Apoenzyme
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an enzyme that is devoid of its necessary cofactor and is thus catalytically inactive
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Holoenzyme
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an enzyme that contains its necessary cofactor and is thus catalytically active
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Zymogen
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an enzyme that is secreted in an inactive form; cleaved under certain physiological conditions to the active form of the enzyme
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