AP Biology Chapter 8 Review

activation energy

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.

cofactor

Any 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 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 others, facilitating binding of subsequent substrate molecules.

endergonic reaction

A nonspontaneous 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 changes 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. (The change in free energy of a system is calculated by the equation ΔG = ΔH - TΔS, where H is enthalpy [in biological systems, equivalent to total energy], T is absolute temperature, and S is entropy.)

Zeroth law of thermodynamics

If two systems are in thermal equilibrium with a third system, they must be in thermal equilibrium with each other. This law helps define the notion of temperature.

Third law of thermodynamics

The entropy of a system approaches a constant value as the temperature approaches zero. The entropy of a system at absolute zero is typically zero, and in all cases is determined only by the number of different ground states it has.

heat

The 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.

hemoglobin

An iron-containing protein in red blood cells that reversibly binds oxygen.

induced fit

Induced 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 (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).

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.

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 functions effectively.

order

In classification, the taxonomic category above the level of family.

phosphorylated

Referring to a molecule that is covalently bonded to a phosphate group.

potential energy

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

ribose

The sugar component of RNA nucleotides.

second law of thermodynamics

The 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.

substrate

The reactant on which an enzyme works.

thermal energy

See heat.

thermodynamics

The study of energy transformations that occur in a collection of matter. See first law of thermodynamics; second law of thermodynamics.