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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

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 molecules.

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.

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 molecules.

catalyst

A chemical agent that selectively 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.

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, whose structure it mimics.

cooperativity

A kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits

endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings.

energy

The capacity to cause change, especially to do work (to move matter against an opposing force).

energy coupling

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

entropy

A measure of disorder, or randomness.

enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction.

enzyme-substrate complex

A temporary complex formed when an enzyme binds to its substrate molecule(s).

exergonic reaction

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

feedback inhibition

A 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 thermodynamics

The principle of conservation of energy: Energy can be transferred and transformed, but it cannot be created or destroyed.

free energy

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

heat

Thermal energy in transfer from one body of matter to another

induced fit

Caused 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 energy

The energy associated with the relative motion of objects. Moving matter can perform work by imparting motion to other matter.

metabolic pathway

A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule to simpler molecules.

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.

potential energy

The energy that matter possesses as a result of its location or spatial arrangement (structure).

spontaneous process

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

substrate

The reactant on which an enzyme works.

thermal energy

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

thermodynamics

The study of energy transformations that occur in a collection of matter.

second law of thermodynamics

The principle stating that every energy transfer or transformation increases the entropy of the universe. Usable forms of energy are at least partly converted to heat.