An Introduction to Metabolism

activation energy
Click the card to flip 👆
1 / 36
Terms in this set (36)
activation energy
The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.
active site
The specific portion of an enzyme that binds the substrate by means of multiple weak interactions and that forms the pocket in which catalysis occurs.
ATP (adenosine triphosphate)
An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
allosteric regulation
The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.
anabolic pathway
A metabolic pathway that consumes energy to synthesize a complex molecule from simpler compounds.
bioenergetics
(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.
catabolic pathway
A metabolic pathway that releases energy by breaking down complex molecules to simpler compounds.
catalyst
A chemical agent that increases the rate of a reaction without being consumed by the reaction.
chemical energy
Energy available in molecules for release in a chemical reaction; a form of potential energy.
coenzyme
An organic molecule serving as a cofactor. Most vitamins function as coenzymes in metabolic reactions.
cofactorAny nonprotein molecule or ion that is required for the proper functioning of an enzyme. Cofactors can be permanently bound to the active site or may bind loosely with the substrate during catalysis.competitive inhibitorA substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.cooperativityA kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the others, facilitating binding of subsequent substrate molecules.endergonic reactionA nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.energyThe capacity to cause change, especially to do work (to move matter against an opposing force).energy couplingIn cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.entropyA measure of disorder, or randomness.enzymeA macromolecule serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.enzyme-substrate complexA temporary complex formed when an enzyme binds to its substrate molecule(s).exergonic reactionA spontaneous chemical reaction, in which there is a net release of free energy.feedback inhibitionA method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.first law of thermodynamicsThe principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.free energyThe portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system. (The change in free energy of a system is calculated by the equation ?G = ?H - T?S, where H is enthalpy [in biological systems, equivalent to total energy], T is absolute temperature, and S is entropy.)heatThe total amount of kinetic energy due to the random motion of atoms or molecules in a body of matter; also called thermal energy. Heat is energy in its most random form.hemoglobinAn iron-containing protein in red blood cells that reversibly binds oxygen.induced fitInduced by entry of the substrate, the change in shape of the active site of an enzyme so that it binds more snugly to the substrate.kinetic energyThe energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.metabolic pathwayA series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).metabolismThe totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism.noncompetitive inhibitorA substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer functions effectively.phosphorylatedReferring to a molecule that is covalently bonded to a phosphate group.potential energyThe energy that matter possesses as a result of its location or spatial arrangement (structure).riboseThe sugar component of RNA nucleotides.second law of thermodynamicsThe principle stating that every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat.substrateThe reactant on which an enzyme works.thermodynamicsThe study of energy transformations that occur in a collection of matter. See first law of thermodynamics; second law of thermodynamics.