Question 1

Cyanide poisoning is fatal because it inhibits which specific component of the electron transport chain, and what is the immediate cellular consequence?

Accepted Answer

Complex IV; electron flow stops, halting ATP synthesis.

Question 2

Dinitrophenol (DNP) was once used as a diet pill. What is its mechanism of action in mitochondria?

Accepted Answer

It uncouples electron transport from ATP synthesis by making the inner mitochondrial membrane permeable to H$$^+.$$

Question 3

Which of the following best explains why DNP causes increased body temperature?

Accepted Answer

It allows electron transport to continue but dissipates the proton gradient as heat instead of making ATP.

Question 4

Which of the following organisms is an example of an obligate anaerobe?

Accepted Answer

Clostridium botulinum

Question 5

In the absence of oxygen, some prokaryotes use alternative terminal electron acceptors. Which of the following is a possible by-product of anaerobic respiration using sulfate ($$\mathrm{SO_4$^{2-}}) as $$the terminal electron acceptor?

Accepted Answer

$$\mathrm{H_2S}$$

Question 6

During intense exercise, human muscle cells switch to lactic acid fermentation. What is the primary reason for this metabolic shift?

Accepted Answer

To regenerate NAD$$^+ so $$glycolysis can continue in the absence of sufficient oxygen.

Question 7

Which of the following foods is produced using alcohol fermentation?

Accepted Answer

Beer

Question 8

Why do nerve cells in the brain die rapidly if deprived of oxygen?

Accepted Answer

They lack enzymes for fermentation and cannot make ATP without oxygen.

Question 9

Which enzyme is the key regulatory point in glycolysis, and how is it regulated?

Accepted Answer

Phosphofructokinase (PFK); inhibited by ATP and citrate, stimulated by AMP

Question 10

Which of the following best describes the fate of excess glucose in a cell?

Accepted Answer

It can be stored or used in other metabolic pathways to make required molecules.

Question 11

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation allows glycolysis to continue by regenerating NAD$$^+ in $$the absence of an electron transport chain.

Question 12

Which of the following is a product of lactic acid fermentation?

Accepted Answer

Lactate

Question 13

Which of the following equations correctly represents the hydrolysis of ATP?

Accepted Answer

$$\mathrm{ATP \rightarrow ADP + P_i + energy}$$

Question 14

Which of the following best explains why citrate inhibits phosphofructokinase (PFK) in glycolysis?

Accepted Answer

Citrate signals that the Krebs cycle is active and the cell does not need more ATP.

Question 15

Which of the following is NOT a general feature of cell division in both prokaryotes and eukaryotes?

Accepted Answer

Mitochondria are distributed equally to daughter cells.

Question 16

Which of the following statements about the use of alternative metabolic pathways is correct?

Accepted Answer

Proteins, fats, and carbohydrates can all be broken down to enter glycolysis or the Krebs cycle.

Question 17

Which of the following best describes the role of AMP in the regulation of glycolysis?

Accepted Answer

AMP stimulates glycolysis by activating PFK.

Question 18

Which of the following is a real-world consequence of the inability of nerve cells to perform fermentation?

Accepted Answer

A stroke causes rapid cell death in the brain due to lack of ATP production.

LEC 14:Inhibitors, Alternative Pathways, and Regulation of Cellular Respiration

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