Question 1

Which of the following best describes the relationship between enzyme activity and pH, as shown in the provided graphs?

Accepted Answer

Enzyme activity is highest at an optimal pH and decreases at both lower and higher pH values.

Question 2

A student observes that catalase activity is nearly zero at pH 2 and pH 13. What is the most likely explanation for this observation?

Accepted Answer

Catalase is denatured at extreme pH values, losing its functional shape.

Question 3

Which of the following equations correctly represents the breakdown of hydrogen peroxide by catalase?

Accepted Answer

$$2\ \mathrm{H}_2\mathrm{O}_2 \rightarrow 2\ \mathrm{H}_2\mathrm{O} + \mathrm{O}_2$$

Question 4

Refer to the temperature vs. enzyme activity graph. At what temperature does catalase activity reach its maximum?

Accepted Answer

$$37^\circ\mathrm{C}$$

Question 5

What is the most likely outcome if catalase is exposed to a temperature of $$90^\circ\mathrm{C}$$, as shown in the data table?

Accepted Answer

Catalase will be denatured and lose almost all activity.

Question 6

Which amino acid structure shown is most likely to be hydrophobic?

Accepted Answer

The structure with a side chain containing only hydrocarbons (valine).

Question 7

Which level of protein structure is directly affected by denaturation, as seen when an egg is cooked?

Accepted Answer

Tertiary structure

Question 8

A solution is described as having $$[\mathrm{H}^+] = [\mathrm{OH}^-]. $$Which label best fits this solution?

Accepted Answer

Neutral solution

Question 9

Why do enzymes such as catalase have an optimal pH and temperature?

Accepted Answer

Their three-dimensional structure is stabilized only under specific conditions.

Question 10

If a student accidentally adds a strong acid to a catalase reaction, what is the most likely effect on enzyme activity?

Accepted Answer

Enzyme activity will decrease due to denaturation.

Question 11

Which of the following best explains why catalase is highly specific for hydrogen peroxide?

Accepted Answer

The enzyme's active site has a unique shape that fits only hydrogen peroxide.

Question 12

A student measures the height of foam produced in a catalase experiment. What does the foam represent?

Accepted Answer

Oxygen gas produced from the breakdown of hydrogen peroxide.

Question 13

Which of the following is a correct interpretation of the effect of temperature on catalase activity, based on the provided graph?

Accepted Answer

Catalase activity increases with temperature up to an optimum, then decreases sharply.

Question 14

Which of the following best describes the quaternary structure of a protein?

Accepted Answer

The arrangement of multiple polypeptide subunits in a functional protein.

Question 15

If a catalase experiment is repeated at pH 7 and pH 11, and the foam height is greater at pH 7, what can be concluded?

Accepted Answer

Catalase has higher activity at pH 7, which is closer to its optimum pH.

Question 16

Which of the following amino acids is most likely to be found on the surface of a protein in an aqueous environment?

Accepted Answer

Glutamate, due to its charged carboxyl group.

Question 17

A student hypothesizes that catalase activity will be highest at body temperature. Which data would best support this hypothesis?

Accepted Answer

The average foam height is highest at $$37^\circ\mathrm{C}$$ compared to other temperatures.

Question 18

Which of the following best explains why proteins denature at high temperatures?

Accepted Answer

High temperatures disrupt hydrogen bonds and other interactions stabilizing the protein's structure.

Question 19

Which of the following is a real-life example of irreversible protein denaturation?

Accepted Answer

Cooking an egg white, causing it to turn from clear to white.

Lab 6: Enzymes – Effects of pH and Temperature on Catalase Activity

Study Guide - Practice Questions