Question 1

Why does glucose not spontaneously combust when exposed to oxygen at room temperature, even though the reaction $$\mathrm{C_6H_{12}O_6$ + 6\ O_2$ \rightarrow 6\ CO_2$ + 6\ H_2O}$$ has a negative $$\Delta G$$?

Accepted Answer

Energy is required for the sugar and oxygen to reach their transition state.

Question 2

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

Accepted Answer

It is the energy required to bring reactants to the transition state.

Question 3

A laboratory experiment increases the temperature of a reaction mixture from $$10^\circC to$$ $$40^\circC. $$What is the most likely effect on the reaction rate, and why?

Accepted Answer

The reaction rate will increase because more molecules have enough energy to reach the transition state.

Question 4

Which of the following changes would most likely increase the rate of a chemical reaction in the absence of an enzyme?

Accepted Answer

Increasing the concentration of reactants.

Question 5

What is the primary function of the active site of an enzyme?

Accepted Answer

It is involved in the catalytic reaction of the enzyme.

Question 6

Can an enzyme make a nonspontaneous reaction occur spontaneously? Why or why not?

Accepted Answer

No, because enzymes do not affect the overall $$\Delta G of a $$reaction.

Question 7

A patient with a high fever (body temperature of $$41^\circC) is at $$risk for enzyme denaturation. What is the most likely consequence for their metabolic enzymes?

Accepted Answer

The enzymes may denature, losing their three-dimensional structure and function.

Question 8

Which of the following best explains why pepsin, a digestive enzyme in the stomach, has maximal activity at low pH?

Accepted Answer

Pepsin's structure is stabilized by the acidic environment, allowing optimal catalysis.

Question 9

A metabolic pathway consists of three enzymes: Enzyme 1, Enzyme 2, and Enzyme 3. If the end product arginine inhibits Enzyme 3, what is the most likely result?

Accepted Answer

The pathway will slow or stop, leading to accumulation of the intermediate just before Enzyme 3.

Question 10

Which of the following statements about competitive inhibition is correct?

Accepted Answer

A competitive inhibitor binds to the active site, preventing substrate binding.

Question 11

How might covalent modification (such as phosphorylation) of an amino acid residue distant from the active site alter an enzyme's substrate specificity?

Accepted Answer

By changing the shape of the enzyme.

Question 12

Which of the following best describes the effect of an enzyme on the activation energy ($$E_a) $$and the free energy change ($$\Delta G) of a $$reaction?

Accepted Answer

An enzyme lowers $$E_a$$ but does not change $$\Delta G.$$

Question 13

A scientist adds a noncompetitive inhibitor to an enzyme-catalyzed reaction. What is the most likely effect on the enzyme's activity?

Accepted Answer

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

Question 14

In a metabolic pathway, if the concentration of the end product increases and binds to an allosteric site on the first enzyme, what type of regulation is this?

Accepted Answer

Feedback inhibition

Question 15

Which of the following is a real-world example of how temperature affects enzyme activity in humans?

Accepted Answer

Enzymes in the human body denature at temperatures significantly above $$37^\circC.$$

Question 16

A researcher observes that increasing substrate concentration increases the rate of an enzyme-catalyzed reaction, but only up to a certain point. What is the most likely explanation?

Accepted Answer

The enzyme becomes saturated with substrate, and the reaction rate reaches a maximum (Vmax).

Question 17

Which of the following best explains why enzymes are highly specific for their substrates?

Accepted Answer

The active site of the enzyme has a unique shape that fits only specific substrates.

Question 18

A mutation causes an enzyme to lose its ability to bind a cofactor. What is the most likely result?

Accepted Answer

The enzyme will lose its catalytic activity.

Question 19

Which of the following statements about metabolic pathways is correct?

Accepted Answer

Each step in a metabolic pathway is catalyzed by a different enzyme.

Energy and Enzymes: Principles of Chemical Reactions in Biology

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드