Chapter 8

Question 1

metabolic pathway

Answer 1

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

Question 2

catabolic pathway

Answer 2

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

Question 3

anabolic pathway

Answer 3

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

Question 4

bioenergetics

Answer 4

the study of how energy flows through living organisms

Question 5

thermodynamics

Answer 5

the study of the energy transformations that occur in a collection of matter

Question 6

first law of thermodynamics

Answer 6

energy of the universe is constant; it can be transferred and transformed, but it cannot be created or destroyed

Question 7

entropy

Answer 7

a measure of molecular disorder or randomness

Question 8

second law of thermodynamics

Answer 8

every energy transfer or transformation increases the entropy of the universe

Question 9

spontaneous process

Answer 9

a process that leads to an increase in entropy and can proceed without requiring an input of energy

Question 10

free energy

Answer 10

the portion of a system’s energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell

Question 11

change in free energy equation

Answer 11

deltaG=deltaH-TdeltaS
change in free energy=change in enthalpy - temperature x change in entropy

Question 12

exergonic reaction

Answer 12

net release of free energy

Question 13

endergonic reaction

Answer 13

absorbs free energy from its surroundings

Question 14

energy coupling

Answer 14

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

Question 15

ATP

Answer 15

contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups (the triphosphate group) bonded to it

Question 16

phosphorylated intermediate

Answer 16

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

Question 17

enzyme

Answer 17

macromolecule that acts as a catalyst, a chemical agent that speeds up a reaction without being consumed by the reaction; cannot turn a reaction from exergonic to endergonic and vise versa

Question 18

activation energy

Answer 18

the energy required to contort the reactant molecules so the bonds can break; the amount of energy needed to push the reactants to the top of an energy barrier

Question 19

catalysis

Answer 19

the process where a catalyst selectively speeds up a reaction without being consumed

Question 20

substrate

Answer 20

a reactant an enzyme acts on

Question 21

enzyme substrate complex

Answer 21

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

Question 22

active site

Answer 22

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

Question 23

induced fit

Answer 23

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 24

cofactor

Answer 24

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 25

coenzyme

Answer 25

an organic molecule serving as a cofactor. most vitamins function as coenzymes in metabolic reactions

Question 26

competitive inhibitors

Answer 26

reduce the productivity of enzymes by blocking substrates from entering active sites

Question 27

noncompetitive inhibitors

Answer 27

do not directly compete with the substrate to bind to the enzyme at the active site. instead, they impede enzymatic reactions by binding to another part of the enzyme. this interaction causes the enzyme molecule to change its shape in such a way that the active site becomes much less effective at catalyzing the conversion of substrate to product

Question 28

allosteric regulation

Answer 28

any case in which a protein’s function at one site is affected by the binding of a regulatory molecule to a separate site. it may result in either inhibition or stimulation of an enzyme’s activity

Question 29

cooperativity

Answer 29

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 30

feedback inhibition

Answer 30

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