Question 1

Which of the following best describes how the cell makes the synthesis of glutamine from glutamic acid spontaneous?

Accepted Answer

By coupling the reaction to the hydrolysis of ATP, which has a highly negative $$\Delta G$$

Question 2

What is the net change in free energy ($$\Delta G) $$for the coupled reaction of glutamine synthesis, given $$\Delta G_{Glu} = +14.2 kJ/$$mol and $$\Delta G_{ATP} = -30.5 kJ/$$mol?

Accepted Answer

$$\Delta G = -16.3 kJ/$$mol

Question 3

Which statement about enzymes is correct?

Accepted Answer

Enzymes lower the activation energy ($$E_A) $$but do not change $$\Delta G$$

Question 4

The hydrolysis of sucrose to glucose and fructose is catalyzed by sucrase. Which of the following is true about this reaction?

Accepted Answer

The reaction is exergonic with $$\Delta G = -29.3 kJ/$$mol

Question 5

Which of the following is NOT a way that enzymes lower the activation energy of a reaction?

Accepted Answer

Increasing the $$\Delta G of $$the reaction

Question 6

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Competing with the substrate for binding at the active site

Question 7

Which of the following statements about non-competitive inhibitors is correct?

Accepted Answer

They bind to a different site and alter enzyme function

Question 8

What is the effect of increasing temperature on enzyme activity in most human enzymes?

Accepted Answer

Activity increases up to an optimal temperature, then rapidly declines due to denaturation

Question 9

Which enzyme would be most active at pH 2, based on the provided graph?

Accepted Answer

Pepsin

Question 10

If the concentration of product B increases in a reaction where $$\Delta G is $$near zero, what is likely to happen?

Accepted Answer

The reaction will reach equilibrium and may proceed in reverse

Question 11

Which of the following is an example of allosteric regulation?

Accepted Answer

A molecule binding to a site other than the active site and affecting enzyme function

Question 12

What is the main reason why enzymes are sensitive to environmental conditions such as pH and temperature?

Accepted Answer

Protein structure is sensitive to the environment, affecting enzyme shape and function

Question 13

Which of the following is true about enzyme cofactors?

Accepted Answer

Cofactors can be inorganic ions or organic molecules (coenzymes)

Question 14

What happens to an enzyme when it is exposed to temperatures above its optimal range?

Accepted Answer

It loses its shape due to disruption of weak interactions (denaturation)

Question 15

Which of the following best explains why reactions do not usually go to completion in cells?

Accepted Answer

Reactions reach a state of equilibrium where both reactants and products are present

Question 16

Which of the following is a plausible consequence of removing product B from a reaction at equilibrium?

Accepted Answer

More reactant A will be converted to product B

Question 17

Which statement about enzyme-substrate complexes is correct?

Accepted Answer

The enzyme changes shape to enfold the substrate (induced fit)

Question 18

Which of the following is true about feedback inhibition?

Accepted Answer

It is a form of allosteric regulation where the end product inhibits an earlier enzyme

Question 19

Which of the following is a correct definition of activation energy ($$E_A$$)?

Accepted Answer

The initial energy needed to start a chemical reaction

Question 20

Which of the following would most likely increase the rate of an enzyme-catalyzed reaction, assuming all other conditions are optimal?

Accepted Answer

Increasing the concentration of substrate

LEC 10: Enzyme Structure, Function, and Regulation

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