Chapter 8 Key Terms

Question 1

activation energy

Answer 1

The amount of energy that reactants must absorb before a chemical reaction will start; also called activation energy.

Question 2

active site

Answer 2

The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.

Question 3

allosteric regulation

Answer 3

The binding of a molecule to a protein that affects the function of the protein at a different site.

Question 4

anabolic pathway

Answer 4

A metabolic pathway that synthesizes a complex molecule from simpler compounds.

Question 5

ATP (adenosine triphosphate)

Answer 5

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.

Question 6

bioenergetics

Answer 6

The flow of energy through an animal, taking into account the energy stored in the food it consumes, the energy used for basic functions, activity, growth, reproduction, and regulation, and the energy lost to the environment as heat or in waste.

Question 7

catabolic pathway

Answer 7

A metabolic pathway that releases energy by breaking down complex molecules to simpler compounds.

Question 8

catalyst

Answer 8

A chemical agent that changes the rate of a reaction without being consumed by the reaction.

Question 9

chemical energy

Answer 9

Energy stored in the chemical bonds of molecules; a form of potential energy.

Question 10

coenzyme

Answer 10

An organic molecule serving as a cofactor. Most vitamins function as coenzymes in important metabolic reactions.

Question 11

cofactor

Answer 11

Any non-protein 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.

Question 12

competitive inhibitor

Answer 12

A substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.

Question 13

cooperativity

Answer 13

An interaction of the constituent subunits of a protein whereby a conformational change in one subunit is transmitted to all the others.

Question 14

endergonic reaction

Answer 14

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

Question 15

energy

Answer 15

The capacity to do work (to move matter against an opposing force).

Question 16

energy coupling

Answer 16

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

Question 17

entropy

Answer 17

A quantitative measure of disorder or randomness, symbolized by S.

Question 18

enzyme

Answer 18

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

Question 19

enzyme-substrate complex

Answer 19

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

Question 20

exergonic reaction

Answer 20

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

Question 21

feedback inhibition

Answer 21

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

Question 22

first law of thermodynamics

Answer 22

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

Question 24

free energy of activation

Answer 24

The portion of a 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- T Δs, where T is absolute temperature.

Question 25

heat

Answer 25

thermal energy; The total amount of kinetic energy due to molecular motion in a body of matter. Heat is energy in its most random form.

Question 26

induced fit

Answer 26

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate.

Question 27

kinetic energy

Answer 27

The energy of motion, which is directly related to the speed of that motion. Moving matter does work by imparting motion to other matter.

Question 28

metabolic pathway

Answer 28

A series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule into simpler compounds (catabolic pathway).

Question 29

metabolism

Answer 29

The totality of an organism’s chemical reactions, consisting of catabolic and anabolic pathways.

Question 30

non-competitive inhibitor

Answer 30

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

Question 31

phosphorylated

Answer 31

Referring to a molecule that has been the recipient of a phosphate group.

Question 32

potential energy

Answer 32

The energy stored by matter as a result of its location or spatial arrangement.

Question 33

second law of thermodynamics

Answer 33

The principle whereby every energy transfer or transformation increases the entropy of the universe. Ordered forms of energy are at least partly converted to heat, and in spontaneous reactions, the free energy of the system also decreases.

Question 34

substrate

Answer 34

The reactant on which an enzyme works.

Question 35

thermodynamics

Answer 35

(1) The study of energy transformations that occur in a collection of matter. (2) A phenomenon in which external DNA is taken up by a cell and functions there.