Q: Which of the following equations correctly represents the net ATP yield from substrate-level phosphorylation during the complete aerobic catabolism of one molecule of glucose?

$$2 \text{ ATP (glycolysis)} + 2 \text{ GTP (TCA cycle)} = 4 \text{ ATP}$$

Q: Calculate the total number of ATP molecules generated from the complete aerobic respiration of one molecule of glucose, including both substrate-level and oxidative phosphorylation.

$$2 \text{ ATP (glycolysis)} + 2 \text{ GTP (TCA)} + 34 \text{ ATP (oxidative phosphorylation)} = 38 \text{ ATP}$$

Question 1

Which of the following best explains why glycolysis alone is insufficient to sustain life in most chemoorganotrophs?

Accepted Answer

Glycolysis lacks redox balance, leading to an accumulation of NADH and depletion of NAD$$^+.$$

Question 2

During the transition reaction, what are the products generated from one molecule of pyruvate?

Accepted Answer

1 NADH, 1 CO$$_2$$, 1 Acetyl-CoA

Question 3

Which of the following equations correctly represents the net ATP yield from substrate-level phosphorylation during the complete aerobic catabolism of one molecule of glucose?

Accepted Answer

$$2 	ext{ ATP (glycolysis)} + 2 	ext{ GTP (TCA cycle)} = 4 	ext{ ATP}$$

Question 4

What is the primary function of the glyoxylate cycle in bacteria growing on acetate as a carbon source?

Accepted Answer

To regenerate oxaloacetate for the TCA cycle and enable biosynthesis from C2 compounds

Question 5

Which of the following best describes the role of the proton motive force (pmf) in ATP synthesis?

Accepted Answer

The pmf generates torque in ATP synthase, driving the conversion of ADP and Pi to ATP.

Question 6

In the electron transport chain, what is the fate of electrons donated by NADH?

Accepted Answer

They are transferred to oxygen, forming water as the terminal product.

Question 7

Calculate the total number of ATP molecules generated from the complete aerobic respiration of one molecule of glucose, including both substrate-level and oxidative phosphorylation.

Accepted Answer

$$2 	ext{ ATP (glycolysis)} + 2 	ext{ GTP (TCA)} + 34 	ext{ ATP (oxidative phosphorylation)} = 38 	ext{ ATP}$$

Question 8

Which of the following statements about fermentation is correct?

Accepted Answer

Fermentation achieves redox balance by reducing an organic molecule derived from the original substrate.

Question 9

A culture of yeast is fermenting glucose in the absence of oxygen. What are the main products excreted by the yeast?

Accepted Answer

Ethanol and CO$$_2$$

Question 10

Which of the following best explains why lactic acid bacteria can survive in environments lacking external electron acceptors?

Accepted Answer

They reduce pyruvate to lactic acid, regenerating NAD$$^+$$ for glycolysis.

Question 11

Which of the following is a major biosynthetic role of the citric acid cycle (TCA cycle)?

Accepted Answer

Generation of precursors for amino acid and fatty acid biosynthesis

Question 12

E. coli is grown in three different conditions: (A) aerobic respiration with O$$_2$$, (B) anaerobic respiration with nitrate, and (C) fermentation. In which condition will E. coli have the highest growth rate and why?

Accepted Answer

Condition A, because aerobic respiration yields the most ATP per glucose molecule.

Question 13

Which of the following equations correctly represents the ATP yield from the oxidation of NADH and FADH$$_2$$ during oxidative phosphorylation?

Accepted Answer

$$1 	ext{ NADH} ightarrow 3 	ext{ ATP};\ 1 	ext{ FADH}_2 ightarrow 2 	ext{ ATP}$$

Question 14

A bacterium is growing on glucose in the absence of oxygen and external electron acceptors. Which metabolic pathway will it most likely use to regenerate NAD$$^+$$?

Accepted Answer

Fermentation

Question 15

Which of the following best describes substrate-level phosphorylation (SLP)?

Accepted Answer

Direct transfer of a phosphate group to ADP from a phosphorylated intermediate

Question 16

Which of the following is NOT a product of the citric acid cycle per molecule of acetyl-CoA oxidized?

Accepted Answer

1 pyruvate

Question 17

Which of the following statements about the electron transport chain (ETC) is correct?

Accepted Answer

The ETC establishes a proton gradient across the membrane, which is used to synthesize ATP.

Question 18

Which of the following is a key difference between oxidative phosphorylation and photophosphorylation?

Accepted Answer

Oxidative phosphorylation uses a proton motive force generated by electron flow from organic molecules, while photophosphorylation uses a proton motive force generated by light-driven electron flow.

Question 19

Which of the following best explains why fermentation products such as lactic acid and ethanol are considered 'waste' by fermenting microbes?

Accepted Answer

They are highly reduced and excreted to maintain redox balance.

Lecture 11 Microbio

Guida di studio - Domande di pratica

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