BIO103 Unit 3 Terms

Question Answer
Energy The capacity to do work.
kinetic energy The energy of motion kinetic
first law of thermodynamics Energy cannot be created or destroyed.
entropy measure of how much the energy of a system is dispersed
second law of thermodynamics Energy tends to disperse spontaneously.
potential energy Energy stored in the position or arrangement of a system’s components.
reactants Molecule that enters a reaction and is changed by participating in it.
endergonic Describes a reaction that requires a net input of free energy.
exergonic Describes a reaction that ends with a net release of free energy.
Activation energy Minimum amount of energy required to start a reaction.
catalysis The acceleration of a reaction rate by a molecule that is unchanged by participating in the reaction.
active sites Pocket in an enzyme where substrates react and are converted to products
substrates Molecule that an enzyme acts upon and converts to a product; reactant in an enzyme-catalyzed reaction.
induced-fit model Of enzyme activity, interacting with a substrate causes the active site to change shape so that the fit between them improves and catalysis occurs.
metabolic pathway Series of enzyme-mediated reactions by which cells build, remodel, or break down an organic molecule.
allosteric regulation Control of an enzyme’s activity by a regulatory molecule that binds outside the active site.
feedback inhibition Regulatory mechanism in which a change that results from some activity decreases or stops the activity.
redox reaction A typical reaction is an electron transfer, in which one molecule accepts electrons (it becomes reduced) from another molecule (which becomes oxidized)
electron transfer chain In a cell membrane, series of enzymes and other molecules that accept and give up electrons, thus releasing the energy of the electrons in small, usable steps.
cofactors A coenzyme or metal ion that associates with an enzyme and is necessary for its function.
coenzymes An organic cofactor.
antioxidants substance that interferes with the oxidation of other molecules.
phosphorylation Reaction in which a phosphate group is added to a molecule.
ATP/ADP cycle Process by which cells regenerate ATP. ADP forms when a phosphate group is removed from ATP, then ATP forms again as ADP gains a phosphate group.
CAM plants Type of plant that conserves water by fixing carbon twice, at different times of day.
C4 plants Type of plant that minimizes photorespiration by fixing carbon twice, in two cell types.
photorespiration Pathway initiated by rubisco when it attaches oxygen instead of carbon dioxide to RuBP (ribulose bisphosphate).
C3 plants Type of plant that uses only the Calvin–Benson cycle to fix carbon.
stomata Gaps that open on plant surfaces; allow water vapor and gases to diffuse into and out of plant tissues.
rubisco Ribulose bisphosphate carboxylase. Carbon-fixing enzyme of the Calvin–Benson cycle.
carbon fixation Process by which carbon from an inorganic source such as carbon dioxide is incorporated into an organic molecule
Calvin–Benson cycle Cyclic carbon-fixing pathway that builds sugars from CO 2 ; the light-independent reactions of photosynthesis
electron transfer phosphorylation Process in which electron flow through electron transfer chains sets up a hydrogen ion gradient that drives ATP formation.
photolysis Process by which light energy breaks down a molecule.
photosystem Large protein complex in the thylakoid membrane; consists of pigments and other molecules that collectively convert light energy to chemical energy in photosynthesis.
chlorophyll a Main photosynthetic pigment in plants.
pigment An organic molecule that can absorb light of certain wavelengths.
wavelength Distance between the crests of two successive waves.
stroma Thick, cytoplasm-like fluid between the thylakoid membrane and the two outer membranes of a chloroplast.
thylakoid membrane Inner membrane system that carries out light-dependent reactions in chloroplasts and cyanobacteria.
light-independent reactions Second stage of photosynthesis; use ATP and NADPH to assemble sugars from water and CO 2 .
light-dependent reactions First stage of photosynthesis; convert light energy to chemical energy.
Heterotrophs Organism that obtains carbon from organic compounds assembled by other organisms.
Photosynthesis Metabolic pathway by which most autotrophs use sunlight to make sugars from carbon dioxide and water. Converts light energy into chemical energy.
autotrophs Organism that makes its own food using energy from the environment and carbon from inorganic molecules such as CO 2 .
Lactate fermentation Fermentation pathway that produces ATP and lactate.
Alcoholic fermentation Fermentation pathway that produces ATP, carbon dioxide, and ethanol
citric acid cycle Cyclic pathway that harvests energy from acetyl–CoA; part of aerobic respiration. Also called the Krebs cycle.
substrate-level phosphorylation ATP formation by the transfer of a phosphate group from a phosphorylated molecule to ADP.
pyruvate Three-carbon product of glycolysis.
Glycolysis Set of reactions that convert glucose to two pyruvate for a net yield of two ATP and two NADH.
Fermentation Anaerobic glucose-breakdown pathway that produces ATP without the use of electron transfer chains.
aerobic respiration Oxygen-requiring cellular respiration; breaks down organic molecules (particularly glucose) and produces ATP, carbon dioxide, and water. Includes glycolysis, acetyl–CoA formation, the Krebs cycle, and electron transfer phosphorylation
aerobic Involving or occurring in the presence of oxygen.
Cellular respiration Pathway that uses an electron transfer chain to harvest energy from an organic molecule and make ATP. See aerobic respiration.
anaerobic Occurring in the absence of oxygen.

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