Inhibition of Enzyme Activity

Question 1

Many chemicals can bind to enzymes and either eliminate or drastically reduce their catalytic ability. These chemicals, called

Answer 1

enzyme inhibitors

Question 2

When you take penicillin for a bacterial infection, you are taking _________. Penicillin inhibits several enzymes that are involved in the synthesis of _________

Answer 2

another enzyme inhibitor

bacterial cell walls.

Question 3

Enzyme inhibitors are classified on the basis of whether the inhibition is

Answer 3

reversible or irreversible, competitive or noncompetitive.

Question 4

Reversibility deals with whether the inhibitor will eventually _____from the enzyme, releasing it in the ____ form

Answer 4

dissociate

active

Question 5

Competition refers to whether the inhibitor is a __________________. If so, the inhibitor and substrate will compete for the enzyme active site.

Answer 5

structural analog, or look-alike, of the natural substrate

Question 6

such as arsenic, usually bind very tightly, sometimes even covalently, to the enzyme.

Answer 6

irreversible Inhibitors

Question 7

This generally involves binding of the ____ to one of the ____ of an amino acid in the ____ site.

Answer 7

inhibitor
R groups
active

Question 8

Inhibitor binding may ____ the active site binding groups so that the enzyme-substrate complex ____form. Alternatively, an inhibitor may interfere with the catalytic groups of the active site, thereby effectively ____ catalysis.

Answer 8

block
cannot
eliminating

Question 9

which include snake venoms and nerve gases, generally inhibit many different enzymes.

Answer 9

irreversible inhibitor

Question 10

are often referred to as structural analogs; that is, they are molecules that resemble the structure and charge distribution of the natural substrate for a particular enzyme. Because of this resemblance, the inhibitor can occupy the enzyme active site.

Answer 10

Reversible, competitive enzyme inhibitors

Question 11

However, no reaction can occur, and enzyme activity is

Answer 11

inhbited

Question 12

This inhibition is competitive because the ___and the ___compete for binding to the enzyme ___ site. Thus, the degree of inhibition depends on their ______. If the inhibitor is in excess or binds more strongly to the active site, it will occupy the active site ___frequently, and enzyme activity will be greatly ____. On the other hand, if the natural substrate is present in excess, it will ____frequently occupy the active site, and there will be little ____.

Answer 12

inhibitor
substrate
active
relative concentrations
more
decreased
more
inhibition

Question 13

The sulfa drugs, the first antimicrobics to be discovered, are

Answer 13

competitive inhibitors of a bacterial enzyme needed for the synthesis of the vitamin folic acid.

Question 14

is a vitamin required for the transfer of methyl groups in the biosynthesis of methionine and the nitrogenous bases required to make DNA and RNA.

Answer 14

folic acid

Question 15

can we synthesize folic acid

Answer 15

no

Question 16

Bacteria, on the other hand, ________because they cannot take it in from the environment.

Answer 16

must make folic acid

Question 17

___________ is the substrate for an early step in folic acid synthesis.

Answer 17

para-Aminobenzoic acid (PABA)

Question 18

If the ___substrate (PABA) is bound by the enzyme, the reaction ___, and the bacterium ___. However, if the sulfa drug is present in ____over PABA, it binds ____frequently to the active site of the enzyme. ___folic acid will be produced, and the bacterial cell will ___.

Answer 18

correct
occurs
lives
excess
more
no
die

Question 19

Because we obtain our folic acid from our diets, sulfa drugs

Answer 19

do not harm us