Chapter 8: An Introduction to Metabolism

Question 1

What is energy coupling?

Answer 1

The use of an exergonic process to drive an endergonic one

Question 2

What is the structure of ATP?

Answer 2

a. Sugar ribose
b. Nitrogenous base adenine
c. 3 phosphate goups

Question 3

When ATP undergoes hydrolysis, three types of cellular work/processes are powered. What are they?

Answer 3

a. Chemical
b. Transport
c. Mechanical

Question 4

How is ATP regenerated?

Answer 4

Energy released by breakdown reactions (catabolism) is used to phosphorylate ADP, regenerating ATP

Question 5

What is an enzyme?

Answer 5

Is a macromolecule that acts as a catalyst (chemical agent that speeds up a reaction without being consumed by the reaction)

Question 6

What happens if the enzyme doesn’t function properly?

Answer 6

Chemical traffic through the pathways of metabolism would become terribly congested because many chemical reactions would take such a long time

Question 7

What is activation energy?

Answer 7

Amount of energy needed to push the reactants to the top of an energy barrier, uphill, so that the “downhill” part of the reaction can begin

Question 8

What happens to the activation energy when an enzyme is present?

Answer 8

Lower the activation energy barrier

Question 9

What is a substrate?

Answer 9

Reactant an enzyme acts on

Question 10

What is the enzyme-substrate complex?

Answer 10

a temporary complex formed when enzyme binds to its substrate

Question 11

What is the active site?

Answer 11

Region on the enzyme where the substrate binds

Question 12

What is meant by induced fit?

Answer 12

Tightening of the binding after initial contact — brings chemical groups of the active into positions that enhance their ability to catalyze the chemical reaction

Question 13

What happens when the substrate enters the active site of the enzyme?

Answer 13

Substrates are held in the active site by weak interactions such as hydrogen bonds and ionic bonds — converted to products

Question 14

Why is shape so important for enzyme function?

Answer 14

The specificity of an enzyme shape allows recognition of specific substrate

Question 15

What can alter enzyme activity?

Answer 15

Temperature and pH

Question 16

What is a cofactor?

Answer 16

Nonprotein enzyme helpers

Question 17

What is a competitive inhibitor?

Answer 17

bind to the active site of an enzyme, competing with the substrate

Question 18

What is a noncompetitive inhibitor?

Answer 18

bind to another part of an enzyme, causing the enzyme to change shape and making the active site less effective

Question 19

What is allosteric regulation of enzymes?

Answer 19

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

Question 20

What is cooperativity?

Answer 20

Form of allosteric regulation that can amplify enzyme activity when a substrate molecule binding to one active site in a multi-subunit enzyme triggers a shape change in all subunits, thereby increasing catalytic activity at the other active sites

Question 21

What is feedback inhibition?

Answer 21

a. the end product of a metabolic pathway shuts down the pathway by the inhibitory binding of end product to an enzyme that acts early in the pathway
b. prevents a cell from wasting chemical resources by synthesizing more product than is needed