Question 1

Which of the following best describes the primary function of fermentation in anaerobic prokaryotes?

Accepted Answer

To re-oxidize NADH to NAD$$ ^+ $$ and maintain redox balance when oxygen is not available

Question 2

In the absence of oxygen, which process allows certain prokaryotes to catabolize organic compounds and generate ATP?

Accepted Answer

Fermentation, named after the major end-products generated

Question 3

During fermentation, why is the formation of an energy-rich organic intermediate necessary?

Accepted Answer

It allows for substrate-level phosphorylation to generate ATP

Question 4

Which enzyme catalyzes the transfer of electrons from ferredoxin to protons, resulting in the production of hydrogen gas (H$$_2) $$during fermentation?

Accepted Answer

Hydrogenase

Question 5

What is the role of decarboxylation of organic acids, such as succinate, in microbial fermentation?

Accepted Answer

It generates a sodium or proton motive force across the membrane

Question 6

In the anaerobic food chain, what is the correct sequence of events from the fermentation of organic compounds to the final products?

Accepted Answer

Fermentation to organic acids and alcohols, conversion to CO$$_2$$, H$$_2$$, and acetate, then methanogenesis to CH$$_4$$ and CO$$_2$$

Question 7

Which step in the fermentation pathway of Clostridium propionicum is responsible for the production of propionate?

Accepted Answer

CoA transfer from propionyl-CoA to lactate, catalyzed by CoA transferase

Question 8

If Clostridium propionicum is fermenting glucose via the Embden-Meyerhof-Parnas (EMP) pathway, how many moles of ATP are generated per mole of acetate produced?

Accepted Answer

Two moles

Question 9

Which propionate fermentation pathway yields more ATP per mole of propionate formed?

Accepted Answer

Succinate-propionate pathway

Question 10

Which of the following is a distinguishing feature of homofermentative lactic acid bacteria?

Accepted Answer

They produce lactate as the only or major product of glucose fermentation

Question 11

Mixed acid fermentation, typical of enteric bacteria, results in the production of which combination of end-products?

Accepted Answer

Succinate, lactate, acetate, ethanol, formate, CO$$_2$$, and H$$_2$$

Question 12

Which of the following best explains why only certain compounds are fermentable by microbes?

Accepted Answer

Only compounds that can form an energy-rich intermediate for substrate-level phosphorylation are fermentable

Question 13

A bacterium is fermenting glucose and producing hydrogen gas (H$$_2). $$Which protein and enzyme are most directly involved in this process?

Accepted Answer

Ferredoxin and hydrogenase

Question 14

Which of the following is a real-world application of acetogenic bacteria?

Accepted Answer

Conversion of CO$$_2$$ and H$$_2$$ into acetate in anaerobic digesters

Question 15

A patient’s gut microbiome is dominated by facultative anaerobes performing mixed acid fermentation. Which gases are likely to be detected in their intestinal tract?

Accepted Answer

Hydrogen (H$$_2) $$and carbon dioxide (CO$$_2)$$

Question 16

Which of the following statements about substrate-level phosphorylation in fermentation is correct?

Accepted Answer

It directly generates ATP from ADP and an organic phosphate donor

Question 17

In the context of the anaerobic food chain, what is the ecological significance of methanogens?

Accepted Answer

They convert fermentation end-products into methane, preventing the accumulation of H$$_2$$ and acetate

Question 18

Which of the following best describes the energy yield of the succinate-propionate pathway compared to the acrylate pathway in propionate fermentation?

Accepted Answer

The succinate-propionate pathway yields more ATP per mole of propionate formed

Question 19

Which of the following is NOT a typical end-product of mixed acid fermentation?

Accepted Answer

Methane

Question 20

A researcher is studying a bacterium that exports formate during fermentation, resulting in a proton motive force. Which process is most likely occurring?

Accepted Answer

Oxalate decarboxylation to formate

Microbial Fermentation Pathways and Their Diversity (lecture 6)

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