Ch 7 Enzyme Activity

Question 1

What does the Michaelis–Menten equation describe?

Answer 1

Enzyme kinetics with hyperbolic characteristics

Question 2

What does Vmax represent in the Michaelis–Menten equation?

Answer 2

The maximum rate of reaction

Question 3

What is the relationship expressed by the Michaelis–Menten equation?

Answer 3

V = Vmax[S] / (KM + [S])

Question 4

What type of plot is a Lineweaver-Burk plot?

Answer 4

A plot of 1/V versus 1/[S]

Question 5

In a Lineweaver-Burk plot, what does the x-intercept represent?

Answer 5

-1/KM

Question 6

What does the turnover number (kcat) measure?

Answer 6

Moles of substrate converted to product per unit time by a mole of enzyme

Question 7

What is the turnover number for Carbonic anhydrase?

Answer 7

1,000,000 s–1

Question 8

Who won the Nobel Prize in Chemistry in 2018 for directed evolution of enzymes?

Answer 8

Francis Arnold

Question 9

What is a competitive inhibitor?

Answer 9

A substance that competes with the substrate for the active site

Question 10

True or False: A competitive inhibitor changes Vmax.

Answer 10

False

Question 11

What happens to KM in the presence of a competitive inhibitor?

Answer 11

KM increases

Question 12

What is the effect of noncompetitive inhibition on Vmax?

Answer 12

Vmax decreases

Question 13

In noncompetitive inhibition, what happens to KM?

Answer 13

KM remains unchanged

Question 14

What is feedback inhibition?

Answer 14

Formation of a product inhibits its continued production

Question 15

What is an allosteric enzyme?

Answer 15

A multi-subunit protein whose activity is affected by other substances binding to it

Question 16

What are allosteric effectors?

Answer 16

Substances that modify the behavior of an allosteric enzyme

Question 17

What is the role of kinases in enzyme activity?

Answer 17

They attach phosphates to proteins

Question 18

What is a zymogen?

Answer 18

An inactive precursor of an enzyme

Question 19

What is the active form of chymotrypsinogen called?

Answer 19

α-chymotrypsin

Question 20

What type of modification can activate an enzyme?

Answer 20

Phosphorylation

Question 21

What does the concerted model of allosteric enzymes imply?

Answer 21

The enzyme can only exist in the T or R states

Question 22

Fill in the blank: A protein that controls enzyme activity through phosphorylation of amino acid side chains is called a _______.

Answer 22

kinase

Question 23

Which of the following is an example of a co-enzyme: ATP, a zymogen, biotin, or ATCase?

Answer 23

Biotin

Question 24

Which type of inhibition allows increased substrate concentration to overcome the inhibitor?

Answer 24

Competitive inhibition

Question 25

What does a suicide inhibitor do?

Answer 25

Acts irreversibly on the enzyme

Question 26

What is a co-enzyme example?

Answer 26

Biotin ## Footnote Biotin is a vitamin that acts as a co-enzyme in various biochemical reactions.

Question 27

What is the inactive form of chymotrypsin called?

Answer 27

Chymotrypsinogen ## Footnote Chymotrypsinogen is an inactive precursor that is activated to chymotrypsin.

Question 28

Which enzyme cleaves chymotrypsinogen?

Answer 28

Trypsin ## Footnote Trypsin activates chymotrypsinogen by cleaving it.

Question 29

Where is chymotrypsinogen stored?

Answer 29

Pancreas ## Footnote Chymotrypsinogen is stored in the pancreas before being activated.

Question 30

True or False: Chymotrypsinogen is a multimeric enzyme.

Answer 30

False ## Footnote Chymotrypsinogen is a single polypeptide chain and not multimeric.

Question 31

What is the hydrogen ion concentration in an aqueous solution when the pH is 7.5?

Answer 31

~3.3 X 10^-8 M ## Footnote The hydrogen ion concentration can be calculated using the formula [H+] = 10^(-pH).

Question 32

What is the pH in water when the hydrogen ion concentration is ~3.3 X 10^-7 M?

Answer 32

~6.5 ## Footnote The pH can be determined using the formula pH = -log[H+].