Question 1

Which of the following best describes how enzymes speed up chemical reactions in biological systems?

Accepted Answer

They lower the activation energy required for the reaction to proceed.

Question 2

A scientist is studying an enzyme-catalyzed reaction. She increases the substrate concentration and observes that the reaction rate increases, but eventually levels off even as more substrate is added. What is the most likely explanation for this observation?

Accepted Answer

The enzyme has reached saturation; all active sites are occupied.

Question 3

Which of the following statements about enzyme cofactors is CORRECT?

Accepted Answer

Cofactors can be inorganic ions such as copper, zinc, or iron.

Question 4

Penicillin acts as a competitive inhibitor of the enzyme that builds peptidoglycan in bacteria. Which of the following best explains how penicillin works?

Accepted Answer

Penicillin binds to the active site, preventing the substrate from binding.

Question 5

Which of the following is an example of allosteric regulation of an enzyme?

Accepted Answer

A molecule binds to a site other than the active site, causing a conformational change that alters enzyme activity.

Question 6

A metabolic pathway is regulated by feedback inhibition. Which of the following best describes this process?

Accepted Answer

The final product of the pathway binds to an enzyme early in the pathway, decreasing its activity.

Question 7

Which of the following changes would most likely decrease the activity of a human enzyme?

Accepted Answer

Raising the temperature to 80°C.

Question 8

Which of the following best explains why enzyme activity is affected by pH?

Accepted Answer

pH changes can alter the ionization state of amino acid side chains, affecting enzyme shape and function.

Question 9

A researcher discovers a mutation that changes a single amino acid in the primary structure of an enzyme. What is the most likely consequence?

Accepted Answer

The enzyme's shape and activity may be altered.

Question 10

Which of the following equations best represents the effect of an enzyme on the activation energy ($$E_a) of a $$reaction?

Accepted Answer

$$E_{a,\ enzyme} \u003c E_{a,\ uncatalyzed}$$

Question 11

Which of the following scenarios illustrates non-covalent regulation of enzyme activity?

Accepted Answer

A competitive inhibitor binds reversibly to the active site.

Question 12

If an enzyme-catalyzed reaction is performed at pH 2 and then repeated at pH 7, what is the most likely outcome?

Accepted Answer

The enzyme's activity may increase or decrease depending on its optimal pH.

Question 13

Which of the following best describes the effect of increasing enzyme concentration on the rate of an enzyme-catalyzed reaction, assuming substrate is not limiting?

Accepted Answer

The rate of reaction increases linearly with enzyme concentration.

Question 14

A patient is given a drug that acts as a non-competitive inhibitor of an enzyme. Which of the following best describes how this drug works?

Accepted Answer

It binds to an allosteric site, changing the enzyme's shape and reducing activity.

Question 15

Which of the following is a likely result of covalent modification of an enzyme by phosphorylation?

Accepted Answer

The enzyme's activity can be either increased or decreased, depending on the enzyme.

Question 16

Which of the following best explains why enzymes are not consumed during the reactions they catalyze?

Accepted Answer

Enzymes return to their original conformation after releasing the product.

Question 17

A metabolic pathway is producing too much of its end product. Which regulatory mechanism is most likely to decrease the pathway's activity?

Accepted Answer

Feedback inhibition by the end product binding to an early enzyme.

Question 18

Which of the following is a correct statement about competitive inhibition?

Accepted Answer

It involves the inhibitor binding to the active site of the enzyme.

Question 19

Which of the following best describes the relationship between enzyme structure and function?

Accepted Answer

Changes in the shape of an enzyme can alter its activity.

Week 5 - Sept 29

Study Guide - Practice Questions

Study Guide - Flashcards