Question 1

Which of the following best describes the chemical transformation shown in the first image, where ethanol is converted to acetaldehyde?

Accepted Answer

It is an oxidation reaction involving the removal of two electrons and two protons from ethanol.

Question 2

In the context of cellular metabolism, which enzyme would most likely catalyze the reaction shown in the second image (ethanol to acetaldehyde via dehydrogenation)?

Accepted Answer

Alcohol dehydrogenase

Question 3

The third image shows the conversion of acetaldehyde to ethanol. Which of the following statements is correct regarding this reaction?

Accepted Answer

It is a reduction reaction, where acetaldehyde gains electrons and protons.

Question 4

In alcoholic fermentation, which molecule acts as the final electron acceptor for the electrons removed from NADH?

Accepted Answer

Acetaldehyde

Question 5

Which of the following best explains why the conversion of ethanol to acetaldehyde is considered a dehydrogenation reaction?

Accepted Answer

Because it involves the removal of a hydrogen atom (as a proton and an electron) from ethanol.

Question 6

During alcoholic fermentation in yeast, which of the following sequences correctly describes the fate of pyruvate?

Accepted Answer

Pyruvate is decarboxylated to acetaldehyde, which is then reduced to ethanol.

Question 7

Which coenzyme is most likely involved in the reduction of acetaldehyde to ethanol during fermentation?

Accepted Answer

NADH

Question 8

What is the primary metabolic purpose of reducing acetaldehyde to ethanol in yeast cells under anaerobic conditions?

Accepted Answer

To regenerate NAD+ so glycolysis can continue

Question 9

Which of the following equations correctly represents the overall reaction for the reduction of acetaldehyde to ethanol?

Accepted Answer

$$ \mathrm{CH_3CHO} + 2[H] \rightarrow \mathrm{CH_3CH_2OH} $$

Question 10

In the context of the reactions shown, which statement best describes the relationship between oxidation and reduction?

Accepted Answer

Oxidation and reduction always occur together; as one molecule is oxidized, another is reduced.

Chemotrophic Energy Metabolism: Glycolysis and Fermentation

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