Question 1

Which of the following best describes the role of activation energy ($$E_A) in a $$chemical reaction within a cell?

Accepted Answer

It is the minimum energy required for reactants to reach the transition state and form products.

Question 2

A cell is in a metastable state. What does this mean regarding its reactants and their energy?

Accepted Answer

Reactants are thermodynamically unstable but lack sufficient energy to overcome the activation energy barrier.

Question 3

Why is increasing temperature generally not a viable strategy for overcoming activation energy barriers in biological systems?

Accepted Answer

Higher temperatures would denature proteins and disrupt cellular function.

Question 4

Enzymes increase the rate of a reaction by:

Accepted Answer

Lowering the activation energy ($$E_A) $$required for the reaction.

Question 5

Which statement about enzyme specificity is correct?

Accepted Answer

Enzymes typically recognize and bind only specific substrates due to the unique structure of their active sites.

Question 6

Which of the following is a common method by which enzymes activate their substrates?

Accepted Answer

Distortion of substrate bonds to make them more susceptible to reaction.

Question 7

A competitive inhibitor affects enzyme activity by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 8

Which of the following best explains why enzymes are effective in small amounts within cells?

Accepted Answer

Enzymes are not permanently changed or consumed during reactions and can catalyze many cycles.

Question 9

Which of the following is an example of irreversible enzyme inhibition used therapeutically?

Accepted Answer

Penicillin binding to bacterial cell wall synthesis enzymes.

Question 10

Allosteric regulation of enzymes involves:

Accepted Answer

Binding of regulatory molecules to a site distinct from the active site, causing a conformational change.

Question 11

Which of the following statements about enzyme-catalyzed reactions is true?

Accepted Answer

Enzymes only affect the rate at which equilibrium is achieved, not the equilibrium itself.

Question 12

Which amino acids are commonly found in enzyme active sites due to their ability to participate in acid-base and electron transfer reactions?

Accepted Answer

Cysteine, histidine, serine, aspartate, glutamate, and lysine.

Question 13

Which of the following best describes feedback inhibition in metabolic pathways?

Accepted Answer

The end-product of a pathway inhibits the first enzyme in the pathway, regulating the pathway's activity.

Question 14

Which statement about enzyme cofactors and coenzymes is correct?

Accepted Answer

Cofactors are metal ions and coenzymes are small organic molecules, both essential for enzyme activity.

Question 15

Which of the following is a consequence of dramatic pH changes on enzyme activity?

Accepted Answer

Disruption of ionic and hydrogen bonds, leading to loss of tertiary structure and enzyme function.

Question 16

Which process involves the irreversible removal of a portion of a polypeptide chain to activate an enzyme?

Accepted Answer

Proteolytic cleavage.

Question 17

Which of the following best explains why zymogens are synthesized in an inactive form in the pancreas?

Accepted Answer

To prevent the enzymes from digesting pancreatic cells before reaching the small intestine.

Question 18

Which of the following is true regarding the effect of temperature on enzyme-catalyzed reactions?

Accepted Answer

Increasing temperature increases kinetic energy and reaction rate up to a point, but excessive heat causes denaturation and loss of activity.

Question 19

Which of the following is a key feature of allosteric enzymes that exhibit cooperativity?

Accepted Answer

Binding of substrate to one subunit affects the affinity of other subunits for substrate.

Chapter 6

Study Guide - Practice Questions