Question 1

Which of the following best distinguishes fermentation from respiration in terms of electron acceptors?

Accepted Answer

Fermentation uses organic compounds as both electron donors and acceptors, while respiration uses an external electron acceptor.

Question 2

During lactic acid fermentation, which enzyme is responsible for reducing pyruvate to lactate, thereby regenerating NAD+?

Accepted Answer

Lactate dehydrogenase

Question 3

Which of the following equations represents the overall reaction for aerobic respiration of glucose?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} + 6\mathrm{O_2$} \rightarrow 6\mathrm{CO_2$} + 6\mathrm{H_2O}$$

Question 4

Which of the following is a key feature of substrate-level phosphorylation in fermentation?

Accepted Answer

ATP is synthesized directly from a high-energy intermediate without the use of an electron transport chain.

Question 5

In the context of fermentation, what is meant by 'energy-rich compound'?

Accepted Answer

A molecule whose hydrolysis is more exergonic than ATP synthesis, allowing direct ATP production.

Question 6

Which of the following best describes the role of syntrophy in secondary fermentations?

Accepted Answer

It allows energetically unfavorable reactions to proceed by coupling them with the consumption of products (e.g., H$$_2) by $$another organism.

Question 7

Which of the following is a typical product of clostridial fermentations that is important for human and livestock health?

Accepted Answer

Butyrate

Question 8

Which pathway is used by heterolactic fermenters to convert glucose to xylulose-5-phosphate?

Accepted Answer

Pentose Phosphate Pathway

Question 9

A fermentation reaction is considered 'secondary' if:

Accepted Answer

Its substrate is a product of another fermentation process.

Question 10

Which of the following reactions is an example of a secondary fermentation that is insufficiently exergonic to support substrate-level phosphorylation but can drive cation pumps?

Accepted Answer

$$\mathrm{Succinate} + \mathrm{H_2O} \rightarrow \mathrm{Propionate} + \mathrm{$$HCO_3$$^-}$$

Question 11

Why is hydrogen ($$\mathrm{H_2$}) $$removal by methanogens critical in syntrophic fermentations?

Accepted Answer

It keeps $$\mathrm{H_2$}$$ concentration low, making the overall reaction exergonic and allowing otherwise unfavorable fermentations to proceed.

Question 12

Which of the following statements about lactic acid bacteria is correct?

Accepted Answer

They belong to the phylum Firmicutes and are important in the food industry.

Question 13

In amino acid fermentations involving a pair of amino acids, what is the role of the 'donor arm'?

Accepted Answer

It is deaminated and oxidized to yield ATP and acetate.

Question 14

Which of the following best explains why fermentation products are often toxic to the producing organism?

Accepted Answer

They are reduced organic compounds that accumulate due to the lack of further metabolism in the absence of external electron acceptors.

Question 15

Which of the following is a correct statement about the energy yield of fermentation compared to respiration?

Accepted Answer

Fermentation yields less ATP per mole of substrate than respiration because it lacks an electron transport chain.

Question 16

Which of the following is a defining feature of primary fermentations?

Accepted Answer

Carbohydrates are used as the fermentation substrate.

Question 17

A patient with a gut microbiome rich in butyrate-producing bacteria is likely to experience which of the following health benefits?

Accepted Answer

Improved colon health due to the anti-inflammatory effects of butyrate.

Question 18

Which of the following best describes the theoretical energy limit required to run a cation pump in secondary fermentations?

Accepted Answer

$$\sim 12\ \mathrm{kJ/mol}$$

Question 19

Which of the following is a correct example of interspecies electron transfer in syntrophy?

Accepted Answer

A fermenter produces $$\mathrm{H_2$}$$, which is immediately consumed by a methanogen, allowing the fermenter to continue its metabolism.

Fermentation and Syntrophy: Microbial Metabolism and Ecological Roles

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