Question 1

Which of the following best describes the role of the active site in enzyme catalysis?

Accepted Answer

It is the site on the enzyme where substrate binding and chemical transformation occur, lowering the activation energy.

Question 2

Which equation correctly represents the conversion of substrate to product in an enzyme-catalyzed reaction?

Accepted Answer

$$E + S \rightarrow ES \rightarrow E + P$$

Question 3

According to the induced-fit model of enzyme-substrate binding, what happens when a substrate binds to an enzyme?

Accepted Answer

The enzyme undergoes a conformational change to better fit the substrate, optimizing interactions.

Question 4

Which of the following statements about the transition state in enzyme catalysis is correct?

Accepted Answer

The transition state is the highest energy state during the reaction, and enzymes stabilize it to lower activation energy.

Question 5

Which type of catalysis involves the formation of a covalent bond between the enzyme and substrate?

Accepted Answer

Covalent catalysis

Question 6

A patient has a mutation that prevents the stabilization of the transition state by an enzyme. What is the most likely consequence?

Accepted Answer

The reaction rate will decrease because the activation energy remains high.

Question 7

Which of the following best explains why polar amino acids are important in enzyme catalysis?

Accepted Answer

They participate in catalysis by stabilizing positive or negative charges during the reaction.

Question 8

Which statement correctly describes the difference between hexokinase and glucokinase in terms of $$K_m$$ values?

Accepted Answer

Glucokinase has a higher $$K_m$$ than hexokinase, indicating lower affinity for glucose.

Question 9

Which of the following is a correct definition of a cofactor?

Accepted Answer

A non-protein chemical compound or metallic ion required for enzyme activity.

Question 10

Which of the following statements about competitive and noncompetitive enzyme inhibitors is correct?

Accepted Answer

Competitive inhibitors compete with the substrate for the active site, while noncompetitive inhibitors bind elsewhere and alter enzyme activity.

Question 11

Which of the following best describes an allosteric inhibitor?

Accepted Answer

It binds to a site other than the active site, causing a conformational change that reduces enzyme activity.

Question 12

Which equation best describes the effect of substrate concentration on the initial velocity ($$v) of an $$enzyme-catalyzed reaction?

Accepted Answer

$$v = \frac{V_{max}[S]}{K_m + [S]}$$

Question 13

A researcher adds a metal ion to an enzyme reaction and observes increased activity. Which type of catalysis is most likely occurring?

Accepted Answer

Metal-ion catalysis

Question 14

Which of the following is true about zymogens?

Accepted Answer

They are inactive precursors of proteases, activated by proteolytic cleavage.

Question 15

Which process is regulated by protein kinases and phosphatases?

Accepted Answer

Covalent modification, such as phosphorylation and dephosphorylation of enzymes

Question 16

A drug acts as a noncompetitive inhibitor of an enzyme. What effect will this have on $$V_{max}$$ and $$K_m$$?

Accepted Answer

$$V_{max}$$ decreases, $$K_m$$ remains unchanged

Question 17

Which of the following scenarios best illustrates the lock-and-key model of enzyme action?

Accepted Answer

A substrate fits perfectly into a rigid active site, like a key into a lock.

Question 18

Which of the following is a function of allosteric activators?

Accepted Answer

They bind to allosteric sites and induce a conformational change that increases enzyme activity.

Question 19

Which of the following best describes the role of G-proteins in signal transduction?

Accepted Answer

They link cell surface receptors to intracellular signaling pathways by binding GTP and undergoing conformational changes.

Enzyme Structure, Function, and Catalysis: Biochemistry Study Notes

Guida di studio - Domande di pratica