Q: Which of the following is the correct equation for the reaction catalyzed by catecholase?

$$\text{Catechol} + \frac{1}{2} O_2$ \xrightarrow{\text{Catecholase}} \text{Benzoquinone} + H_2O$$

Question 1

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

Accepted Answer

They lower the activation energy ($$E_A) $$required for the reaction.

Question 2

A student is measuring the rate of an enzyme-catalyzed reaction. If the substrate concentration is increased and all enzyme active sites are occupied, what will happen to the reaction rate?

Accepted Answer

The reaction rate will plateau and not increase further.

Question 3

Which of the following statements about enzyme specificity is correct?

Accepted Answer

Enzymes bind to their substrates at the active site, forming an enzyme-substrate complex.

Question 4

The hydrolysis of sucrose by sucrase produces which two monosaccharides?

Accepted Answer

Glucose and fructose

Question 5

Which of the following best explains why enzymes have an optimal pH?

Accepted Answer

Changes in pH can alter the enzyme's structure, affecting its activity.

Question 6

A competitive inhibitor affects an enzyme-catalyzed reaction by:

Accepted Answer

Binding to the active site and preventing substrate binding.

Question 7

In an experiment, you measure the absorbance ($$A) of a $$solution at 540 nm using a spectrophotometer. According to Beer’s Law, what does a higher absorbance indicate?

Accepted Answer

A higher concentration of product in the solution.

Question 8

Which of the following is the correct equation for the reaction catalyzed by catecholase?

Accepted Answer

$$	ext{Catechol} + \frac{1}{2} O_2$ \xrightarrow{	ext{Catecholase}} 	ext{Benzoquinone} + H_2O$$

Question 9

If you perform an enzyme experiment at 0°C, what is the most likely effect on the reaction rate compared to room temperature?

Accepted Answer

The reaction rate will decrease.

Question 10

Why is it important to use a 'blank' when calibrating a spectrophotometer before measuring absorbance?

Accepted Answer

To set a baseline that accounts for absorbance by the solvent and container.

Question 11

Which of the following best describes the effect of increasing enzyme concentration when substrate is abundant?

Accepted Answer

The reaction rate will increase proportionally.

Question 12

A potato extract is used as a source of catecholase in an experiment. Why should the extract be kept cold and tightly capped when not in use?

Accepted Answer

To maintain enzyme stability and prevent denaturation.

Question 13

Which of the following is NOT a way that the active site of an enzyme can lower the activation energy ($$E_A) of a $$reaction?

Accepted Answer

Increasing the free energy ($$\Delta G) of $$the reaction.

Question 14

In a pH experiment, you observe that enzyme activity increases as pH approaches 7, but decreases at pH 10. What is the most likely explanation?

Accepted Answer

The enzyme has an optimal pH near 7, and extreme pH values denature the enzyme.

Question 15

Which of the following best explains why absorbance readings should be taken quickly after mixing enzyme and substrate in a spectrophotometer experiment?

Accepted Answer

The absorbance may not stabilize because the reaction is still occurring.

Question 16

A student forgets to wipe the outside of a test tube before measuring absorbance. What is the most likely consequence?

Accepted Answer

The absorbance reading will be artificially high or low due to interference.

Question 17

Which of the following is true regarding the effect of temperature on enzyme activity?

Accepted Answer

Enzyme activity increases up to an optimal temperature, then decreases as the enzyme denatures.

Question 18

In the catecholase experiment, why is it important to stagger the addition of the last solution to each test tube?

Accepted Answer

To allow accurate timing and measurement of absorbance for each reaction.

Question 19

Which of the following best describes the relationship between transmittance and absorbance in spectrophotometry?

Accepted Answer

As transmittance increases, absorbance decreases.

Question 20

A solution has an absorbance ($$A) of 0.8 at 540 nm. If $$Beer’s Law is $$A = \varepsilon c l$$, where $$\varepsilon is $$the molar absorptivity, $$c is $$concentration, and $$l is $$path length, what happens to $$A if $$the concentration of product doubles?

Accepted Answer

$$A$$ doubles.

Enzymes: Structure, Function, and Experimental Analysis

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