Regulation of Enzyme Activity

Question 1

Enzyme activity is often regulated by the

Answer 1

cell

Question 2

Often the reason for this is to

Answer 2

conserve energy

Question 3

If the cell runs out of chemical energy, it will die; therefore, many mechanisms exist to

Answer 3

conserve cellular energy

Question 4

The simplest mechanism of enzyme regulation is to produce the enzyme only when

Answer 4

the substrate is present

Question 5

This mechanism is used by ____ to regulate the enzymes needed to break down various sugars to yield ____ for cellular work.

Answer 5

bacteria

ATP

Question 6

Thus, the bacteria save energy by producing the enzymes only when a specific sugar ___ is available.

Answer 6

substrate

Question 7

Other mechanisms for regulating enzyme activity include use of

Answer 7

allosteric enzymes, feedback inhibition, production of proenzymes, and protein modification
(amazing friends please pray peace)

Question 8

One type of enzyme regulation involves enzymes that have more than a single binding site. These enzymes, called

Answer 8

allosteric enzymes

Question 9

These enzymes, called allosteric enzymes, have active sites that can be altered by the binding of small molecules called

Answer 9

effector molecules

Question 10

the effector binding alters the shape of the ____ of the enzyme

Answer 10

active site

Question 11

effector binding converts the active site to an inactive configuration

Answer 11

negative allosterism

Question 12

effector binding converts the active site to an active configuration

Answer 12

positive allosterism

Question 13

In either case, binding of the effector molecule regulates enzyme activity by determining whether it will be

Answer 13

active or inactive

Question 14

The third reaction in glycolysis is the transfer of a phosphoryl group from an ATP molecule to a molecule of fructose-6-phosphate. This reaction, shown here, is catalyzed by an enzyme called

Answer 14

phosphofructokinase

Question 15

Phosphofructokinase activity is sensitive to both

Answer 15

positive and negative allosterism

Question 16

For instance, when ATP is present in abundance, it is a signal that the body has

Answer 16

sufficient energy

and the pathway should slow down

Question 17

negative allosteric effector of phosphofructokinase, inhibiting the activity of the enzyme.

Answer 17

ATP

Question 18

an abundance of AMP, which is a precursor of ___, is evidence that the body needs to make ___.

Answer 18

ATP

ATP

Question 19

When AMP binds to an ____ binding site on phosphofructokinase, enzyme activity is ____, speeding up the reaction and the entire pathway. Thus, AMP is a ___________-of the enzyme.

Answer 19

effecotr
increased
positive allosteric effector

Question 20

Allosteric enzymes are the basis for __________biochemical pathways

Answer 20

feedback inhibition

Question 21

Feedback inhibition usually regulates pathways of enzymes involved in the synthesis of a

Answer 21

biological molecule

Question 22

the cell uses feedback inhibition, in which the ___ can shut off the entire pathway for its own synthesis

Answer 22

product

Question 23

Another means of regulating enzyme activity involves the production of the enzyme in an inactive form called a

Answer 23

proenzyme

Question 24

The proenzyme is converted by _____________ to the active form when it has reached the site of its activity.

Answer 24

proteolysis (hydrolysis of the protein)

Question 25

he cells that produce pepsin actually produce an inactive proenzyme, called

Answer 25

pepsinogen

Question 26

Pepsinogen has an additional

Answer 26

42 amino acids

Question 27

In the presence of stomach acid and previously activated pepsin, the extra forty-two amino acids are ______ and the _____ is transformed into the _____

Answer 27

cleaved off
proenzyme
acitve enzyme

Question 28

Proelastase
activator
enzyme

Answer 28

trypsin

elastase

Question 29

Trypsinogen
activator
enzyme

Answer 29

trypsin

trypsin

Question 30

Chymotrypsinogen A
activator
enzyme

Answer 30

Trypsin + chymotrypsin

chymotrypsin

Question 31

Pepsinogen
activator
enzyme

Answer 31

Acid pH + pepsin

pepsin

Question 32

Procarboxypeptidases
activator
enzyme

Answer 32

Trypsin

Carboxypeptidase A, Carboxypeptidase B

Question 33

is another mechanism that the cell can use to turn an enzyme on or off. This is a process in which a chemical group is covalently added to or removed from the protein. This covalent modification either activates the enzyme or turns it off.

Answer 33

protein modification

Question 34

The most common type of protein modification is

Answer 34

phosphorylation or dephosphorylation of an enzyme.

Question 35

typically, the phosphoryl group is added to (or removed from) the R group of

Answer 35

serine, tyrosine, or threonine in the protein chain of the enzyme.

Question 36

Notice that these three amino acids have a free ─___in their R group, which serves as the site for the addition of the ____ group.

Answer 36

OH

phosphoryl

Question 37

The covalent modification of an enzyme’s structure is catalyzed by other

Answer 37

enzymes

Question 38

Protein ____ add phosphoryl groups to a target enzyme, while _____ remove them

Answer 38

kinases

phosphatases

Question 39

in adipose tissue, phosphorylation activates the enzyme __________, an enzyme that breaks triglycerides down to fatty acids and glycerol

Answer 39

triacylglycerol lipase

Question 40

an enzyme involved in the breakdown of glycogen, is also activated by the addition of a phosphoryl group.

Answer 40

Glycogen phosphorylase

Question 41

However, for some enzymes, phosphorylation

Answer 41

inactivates the enzymes

Question 42

This is true for________an enzyme involved in the synthesis of glycogen. When this enzyme is phosphorylated, it becomes inactive.

Answer 42

glycogen synthase

Question 43

The convenient aspect of this type of regulation is the ______. An enzyme can quickly be turned on or off in response to environmental or physiological conditions.

Answer 43

reversibility