Unit 4: Enzymes and Energy

metabolism

the totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism

metabolic pathway

a series of chemical reactions that either builds or breaks down a complex molecule

catabolic pathway

a metabolic pathway that releases energy by breaking down complex molecules to simpler molecules

anabolic pathway

a metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules

energy

the capacity to cause change, especially to do work

kinetic energy

the energy associated with the relative motion of objects; moving matter can perform work by imparting motion to other matter

thermal energy

kinetic energy due to the random motion of atoms and molecules; energy in its most random form

potential energy

the energy that matter possesses as a result of its location or structure

chemical energy

energy available in molecules for release in a chemical reaction; a form of potential energy

free energy

the portion of a biological system’s energy that can perform work when temperature and pressure are uniform throughout the system

exergonic

a spontaneous chemical reaction in which there is a net release of free energy

endergonic

a nonspontaneous chemical reaction in which free energy is absorbed from the surroundings

energy coupling

in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction

ΔG

the change in free energy of a system

spontaneous

a process that occurs without an overall input of energy; a process that is energetically favorable

nonspontaneous

a process that occurs with an overall input of energy

enzyme

a macromolecule serving as a catalyst that increases the rate of a reaction without being consumed by the reaction; most enzymes are proteins

activation energy

the amount of energy that reactants must absorb before a chemical reaction will start

active site

the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs

substrate

the reactant on which an enzyme works

coenzyme

an organic molecule serving as a cofactor; most vitamins function as coenzymes

cofactor

any nonprotein molecule or ion that is required for the proper functioning of an enzyme

competitive inhibitor

a substance that reduces the activity of an enzyme by entering the active site in place of the substrate

noncompetitive inhibitor

a 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 effectively catalyzes the conversion of substrate to product

activator

a protein that binds to DNA and stimulates the gene transcription

reaction rate

how fast a chemical reaction occurs