Deck 10: Regulatory Strategies

Question 1

p-Hydroxymercuribenzoate displaces Zn²⁺ from binding to crucial ______________ residues in ATCase.

Answer 1

cysteine

Question 2

_______________ are multiple forms of homologous enzymes within the same organism that catalyze the same reaction but with different kinetic properties.

Answer 2

Isozymes or Isoenzymes

Question 3

What term describes multiple forms of homologous enzymes found within an organism?

A) zymogens
B) holoenzymes
C) isoenzymes
D) consensus enzymes
E) None of the answers is correct.

Answer 3

C

Question 4

Aspartyl transcarbamylase catalyzes the first step in the synthesis of ______________.

Question 5

Which type of enzymes specifically catalyzes protein phosphorylation?

A) protein ATPase
B) protein transferases
C) protein phosphatases
D) protein kinases
E) None of the answers is correct.

Question 6

Histones are acetylated at specific ________________ residues.

Question 7

The ____________ pathway is activated by exposure of anionic surfaces on ruptured endothelial cells.

Question 8

Which modified amino acid is found in prothrombin that allows for Ca²⁺ binding?

A) acetyl lysine
B) phosphoserine
C) $\gamma$ -carboxyglutamate
D) hydroxyproline
E) None of the answers is correct.

Question 9

The effects of substrates on allosteric enzymes are referred to as ___________________ effects.

Question 10

The less active conformational form of an allosteric enzyme is called the _____.

A) T-state
B) M-state
C) R-state
D) I-state
E) L-state

Question 11

What shape is seen in the kinetic plot of an enzyme that exhibits cooperative binding?

A) sigmoidal
B) hyperbolic
C) parabolic
D) linear
E) None of the answers is correct.

Question 12

A ______________ is an inactive precursor of an enzyme that is activated by a proteolytic cleavage.

Question 13

What term describes enzymes that are activated by proteolytic cleavage?

A) phosphatases
B) isozymes
C) kinases
D) zymogens
E) apoenzymes

Question 14

Which of the following is the most crucial pathway for blood clotting?

A) intrinsic pathway
B) extrinsic pathway
C) coagulation pathway
D) fibrinogen activation pathway
E) prothrombin activation pathway

Question 15

What regulatory mechanism relies on inhibition of the first step of the pathway by the final product of the pathway?

A) competitive inhibition
B) uncompetitive inhibition
C) allosteric inhibition
D) feed-forward inhibition
E) feedback inhibition

Question 16

Removal of protein phosphates is catalyzed by protein _____.

A) phosphate hydrolase
B) phosphatase
C) kinase
D) dephosphorylase
E) None of the answers is correct.

Question 17

Protein kinases add phosphoryl groups to serine, threonine, and _________________ residues in target proteins.

Question 18

Protein kinase A is activated by the binding of ________________ to specific sites on the regulatory subunit.

Question 19

What molecule is required for the proper production of prothrombin?

A) factor Xa
B) factor Va
C) tissue factor
D) fibrin
E) vitamin K

Question 20

Blood serum analysis of ____________________________ isozymes is used in the diagnosis of a myocardial infarction.

Question 21

How does the sequential model differ from the concerted model for allosteric enzymes?

Question 22

Which of the following is an example of a zymogen?

A) pepsinogen
B) procarboxypeptidase
C) T-form of ACTase
D) All of the answers are correct.
E) pepsinogen and procarboxypeptidase

Question 23

Allosteric proteins

A) usually display hyperbolic Michaelis-Menten kinetics.
B) often display cooperativity.
C) always consist of several identical subunits.
D) usually display hyperbolic Michaelis-Menten kinetics and often display cooperativity.
E) All of the answers are correct.

Question 24

Multifunctional protein kinases

A) carry out phosphorylation as well as sulfation reactions.
B) can modify several different targets.
C) conserve energy in the form of ATP from the degradation of proteins.
D) All of the answers are correct.
E) None of the answers is correct.

Question 25

Do allosteric enzymes follow traditional Michaelis-Menten kinetics? Draw a graph of rate relative to substrate concentration for ATCase and compare it to a Michaelis-Menten enzyme.

Question 26

Many allosteric enzymes have two types of subunits, termed

A) catalytic and regulatory.
B) regulatory and allosteric.
C) allosteric and regulatory.
D) R-state and T-state.
E) None of the answers is correct.

Question 27

Changes in ATCase conformation were detected by crystallizing the enzyme in the presence of PALA (N-(phosphonacetyl)-L-aspartate). What is PALA?

A) a radioactive tag that binds to the subunits
B) a substrate analog that resembles the transition state
C) a fluorescent allosteric inhibitor analog
D) All of the answers are correct.
E) None of the answers is correct.

Question 28

What is the function of aspartate transcarbamoylase?

Question 29

How is trypsin activity turned off?

A) by dephosphorylation
B) by binding an inhibitor protein
C) by a second cleavage
D) All of the answers are correct.
E) by dephosphorylation and binding an inhibitor protein

Question 30

Examples of covalent modification include

A) phosphorylation and dephosphorylation.
B) acetylation.
C) ubiquitination.
D) All of the answers are correct.
E) phosphorylation, dephosphorylation, and acetylation.

Question 31

Multifunctional kinases phosphorylate proteins by recognizing related sequences called

A) cAMP binding sequences.
B) calmodulin binding sequences.
C) pseudosubstrate sequences.
D) consensus sequences.
E) palindromes.

Question 32

The regulatory effects of substrates on allosteric enzymes are referred to as _______________ effects.

A) homotropic
B) heterotropic
C) allotropic
D) All of the answers are correct.
E) None of the answers is correct.

Question 33

Blood clotting cascades are controlled mostly by

A) zymogen activation.
B) phosphorylation.
C) allosteric activation.
D) All of the answers are correct.
E) None of the answers is correct.

Question 34

Give several examples of enzymes and proteins that are activated by proteolytic activation.

Question 35

What is (are) the most common strategy(ies) for enzymatic regulation?

A) multiple enzyme forms
B) allosteric control
C) reversible covalent modification
D) proteolytic activation
E) All of the answers are correct.

Question 36

The relaxed form of an allosteric enzyme has _________ affinity for the substrates than the tense form.

A) higher
B) equal
C) lower
D) no
E) None of the answers is correct.

Question 37

One type of hemophilia is due to

A) vitamin K deficiency.
B) loss of the gene for prothrombin.
C) loss of the gene for antihemophilic factor.
D) All of the answers are correct.
E) None of the answers is correct.

Question 38

Why might it have been surprising to find that CTP inhibits ATCase?

Question 39

How is chymotrypsinogen activated?

A) cleavage between an Arg and Ile by chymotrypsin
B) cAMP binding, followed by cleavage by elastase
C) cleavage between an Arg and Ile by trypsin
D) All of the answers are correct.
E) None of the answers is correct.

Question 40

A regulatory mechanism that is NOT readily reversible is

A) phosphorylation.
B) allosteric control.
C) proteolytic cleavage.
D) All of the answers are correct.
E) None of the answers is correct.

Question 41

How is the clotting cascade initiated?

Question 42

What protein is administered after heart attacks to increase survival odds, and what is the biochemistry involved?

Question 43

What is the final step in the clotting pathway?

Question 44

Why are certain forms of lactate dehydrogenase used as heart attack indicators?

Question 45

How can cleavage of a single peptide bond activate a zymogen?

Question 46

Individuals in a royal family suffered from hemophilia and often died early from bleeding. What is the cause of this disease? How is it treated?

Question 47

Why is covalent modification advantageous when compared to proteolytic activation?

Question 48

Describe how the PKA kinase cascade is activated.

Question 49

How does cigarette smoking relate to elastase function?

Question 50

What is the dual action of thrombin?