Question 1

Which of the following best describes the role of cellulases in the production of cellulosic ethanol?

Accepted Answer

Cellulases hydrolyze cellulose into glucose, which is then fermented to produce ethanol.

Question 2

Which enzyme is responsible for breaking the internal bonds of cellulose chains during enzymatic hydrolysis?

Accepted Answer

Endocellulase

Question 3

Why must lignin be removed during the pretreatment step of cellulosic ethanol production?

Accepted Answer

Lignin inhibits the enzymatic activity of cellulases, preventing efficient cellulose breakdown.

Question 4

Which of the following organisms produces cellulases naturally?

Accepted Answer

Bacteroides succinogenes

Question 5

Cellobiose is a disaccharide made up of two glucose molecules connected by a β(1,4)-glucoside linkage. Which enzyme catalyzes the breakdown of cellobiose into glucose?

Accepted Answer

Cellobiase

Question 6

During the colorimetric assay for cellobiase activity, why does the solution turn yellow when placed in a basic solution?

Accepted Answer

The basic solution causes the p-nitrophenol to lose a hydrogen ion, forming a nitrophenolate anion that absorbs violet light and reflects yellow light.

Question 7

Which step in cellulosic ethanol production involves the conversion of glucose to ethanol?

Accepted Answer

Microbial fermentation

Question 8

What is the primary structural component of plant cell walls that is targeted for ethanol production?

Accepted Answer

Cellulose

Question 9

Which equation best represents the hydrolysis of cellobiose by cellobiase?

Accepted Answer

$$\mathrm{C$$_{12}$$H_{22}O$$_{11} + H_2O \rightarrow 2\ C_6H_{12}$$O_6$$}$

Question 10

Which of the following statements about primary and secondary cell walls is correct?

Accepted Answer

Secondary cell walls are more rigid due to the presence of hemicellulose and lignin.

Question 11

A researcher measures the absorbance at 410 nm after adding a basic solution to a cellobiase reaction mixture. What does the absorbance value indicate?

Accepted Answer

The concentration of p-nitrophenol released, which reflects cellobiase activity.

Question 12

Which of the following is a plausible reason why humans cannot digest cellulose?

Accepted Answer

Humans lack the enzymes required to hydrolyze the β(1,4)-glucoside linkages in cellulose.

Question 13

Which of the following best explains why cellulosic ethanol is considered a renewable biofuel?

Accepted Answer

It is produced from plant biomass, which can be regrown and harvested repeatedly.

Question 14

Which enzyme would be most effective in breaking down the terminal ends of cellulose chains to release cellobiose?

Accepted Answer

Exocellulase

Question 15

In the process of cellulosic ethanol production, which step is most likely to be affected if hemicellulose is not cleaved from cellulose?

Accepted Answer

Enzymatic hydrolysis

Question 16

Which of the following best describes the relationship between p-nitrophenol and glucose in the cellobiase-catalyzed reaction using p-nitrophenyl glucopyranoside?

Accepted Answer

They are produced in equimolar amounts during the reaction.

Question 17

A student is investigating the effect of pH on cellobiase activity. Which pH would likely yield the highest enzymatic activity?

Accepted Answer

pH 5

Question 18

Which of the following is a correct sequence of steps for cellulosic ethanol production?

Accepted Answer

Pretreatment → Enzymatic hydrolysis → Microbial fermentation

Question 19

Which of the following best explains why fungal decomposers are important in natural ecosystems?

Accepted Answer

They produce cellulases that break down plant cell walls, recycling nutrients back into the environment.

Cellulases, Cellulose Breakdown, and Biofuel Production

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