Review Questions

Which of the following best describes the role of enzymes?
A) They provide energy for reactions.
B) They increase the activation energy of reactions.
C) They lower the activation energy of reactions.
D) They are consumed during reactions.

Fill in the blank: The specific molecule that an enzyme acts on is called its __________.

The region on an enzyme where the substrate binds is called the __________.

True or False: Enzymes are proteins that speed up chemical reactions without being permanently changed.

Which of the following factors can affect enzyme activity?
A) Temperature
B) pH
C) Substrate concentration
D) All of the above

Match the enzyme-related term (Column A) with the correct description (Column B):

1. Column A

   1. Substrate

   2. Active site

   3. Denaturation

   4. Catalyst

   5. Cofactor

2. Column B
   A. Non-protein helper needed for enzyme activity
   B. Area where substrate binds to enzyme
   C. Substance an enzyme acts on
   D. Substance that speeds up a reaction without being consumed
   E. Loss of enzyme shape due to heat or pH

Fill in the blank: When an enzyme loses its three-dimensional shape and can no longer function, it is said to be __________.

Describe the difference between competitive inhibition and noncompetitive inhibition.

Which of the following is an example of feedback inhibition?
A) A product of a metabolic pathway binds to an enzyme early in the pathway and slows its activity
B) Substrate concentration increases enzyme activity
C) Heat destroys the shape of an enzyme
D) An enzyme lowers activation energy

Short answer: Why does enzyme activity generally increase with temperature up to a point, but then decrease sharply at higher temperatures?

The induced fit model suggests that:
A) Enzymes have rigid active sites that never change
B) Substrates alter their shape to fit into enzymes
C) Enzymes slightly change shape to fit substrates
D) Enzymes break down after one use

Fill in the blank: In feedback inhibition, the accumulation of the __________ of a pathway reduces the activity of enzymes earlier in the pathway.

What effect does a noncompetitive inhibitor have on an enzyme’s active site?

Why is feedback inhibition important for maintaining homeostasis in cells?

Application: Imagine a metabolic pathway with three enzymes (E1, E2, E3) that produce a final product Z. If Z accumulates and inhibits E1, explain what happens to the pathway and why this regulation is beneficial for the cell.