Chapter 8 - An Introduction to Metabolism

Question 1

metabolism

Answer 1

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

Question 2

metabolic pathway

Answer 2

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

Question 3

catabolic pathway

Answer 3

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

Question 4

anabolic pathway

Answer 4

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

Question 5

bioenergetics

Answer 5

(1) The overall flow and transformation of energy in an organism. (2) The study of how energy flows through organisms.

Question 6

energy

Answer 6

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

Question 7

kinetic energy

Answer 7

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

Question 8

heat (thermal energy)

Answer 8

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.

Question 9

potential energy

Answer 9

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

Question 10

chemical energy

Answer 10

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

Question 11

thermodynamics

Answer 11

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

Question 12

first law of thermodynamics

Answer 12

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

Question 13

entropy

Answer 13

A measure of disorder, or randomness.

Question 14

second law of thermodynamics

Answer 14

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.

Question 15

spontaneous process

Answer 15

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

Question 16

free energy

Answer 16

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 (ΔG) is calculated by the equation ΔG = ΔH - TΔS, where ΔH Is the change in enthalpy (in biological systems, equivalent to total energy), T is the absolute temperature, and ΔS is the change in entropy.

Question 17

exergonic reaction

Answer 17

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

Question 18

endergonic reaction

Answer 18

A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.

Question 19

energy coupling

Answer 19

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

Question 20

ATP (adenosine triphosphate)

Answer 20

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 21

phosphorylated intermediate

Answer 21

A molecule (often a reactant) with a phosphate group covalently bonded to it, making it more reactive (less stable) than the unphosphorylated molecule.

Question 22

enzyme

Answer 22

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

Question 23

catalyst

Answer 23

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

Question 24

activation energy

Answer 24

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

Question 25

substrate

Answer 25

The reactant on which an enzyme works.

Question 26

enzyme-substrate complex

Answer 26

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

Question 27

active site

Answer 27

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

Question 28

induced fit

Answer 28

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.

Question 29

cofactor

Answer 29

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 and reversibly, along with the substrate, during catalysis.

Question 30

coenzyme

Answer 30

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

Question 31

competitive inhibitor

Answer 31

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

Question 32

noncompetitive inhibitor

Answer 32

A substance that reduces the activity of an enzyme by binding to a location remove from the active site, changing the enzyme’s shape so that the active site no longer effectively catalyzes the conversion of substrate to product.

Question 33

allosteric regulation

Answer 33

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

Question 34

cooperativity

Answer 34

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.

Question 35

feedback inhibition

Answer 35

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