Q: Which of the following equations correctly represents the reaction catalyzed by phosphofructokinase in glycolysis?

$$\mathrm{F\text{-}6\text{-}P} + \mathrm{ATP} \rightarrow \mathrm{F\text{-}1,6\text{-}P} + \mathrm{ADP}$$

Question 1

Which enzyme catalyzes the conversion of fructose 6-phosphate to fructose 1,6-bisphosphate in glycolysis, and why is this step considered the 'committing step'?

Accepted Answer

Phosphofructokinase; because fructose 1,6-bisphosphate is committed to glycolysis and cannot be used in other pathways.

Question 2

Phosphofructokinase (PFK) is regulated by ATP through two binding sites. What happens when ATP binds to the allosteric site of PFK?

Accepted Answer

The enzyme's conformation changes, inhibiting its activity and slowing glycolysis.

Question 3

A mutation causes the allosteric site of phosphofructokinase to have a much higher affinity for ATP than the active site. What is the most likely consequence for glycolysis?

Accepted Answer

Glycolysis would be inhibited even at low ATP concentrations.

Question 4

Which of the following processes convert NADH to NAD+? Select all that apply.

Accepted Answer

Glycolysis, Oxidative Phosphorylation, Alcohol Fermentation, Lactic Acid Fermentation

Question 5

A triglyceride has three fatty acid chains, each with 10 carbons. How many acetyl-CoA molecules will be formed from these fatty acid chains through beta oxidation?

Accepted Answer

Fifteen

Question 6

Given that the molecular weight of glucose is $$180\ \mathrm{g/mol}$$ and $$C_{10}H$$_{16}$$ is 170$$\ \mathrm{g/mol}$$, and knowing that glucose yields 2 acetyl-CoA and C$$_{10}$$H_{16}$$ yields 6 acetyl-CoA, which molecule provides more theoretical ATP per mole?

Accepted Answer

$$C_{10}H$$_{16}$$, because it yields more acetyl-CoA and thus more ATP.

Question 7

Which of the following best explains why high levels of ATP inhibit phosphofructokinase activity?

Accepted Answer

ATP binds to the allosteric site, causing a conformational change that reduces enzyme activity.

Question 8

During beta oxidation, fatty acids are broken down into two-carbon units. If a fatty acid has 16 carbons, how many rounds of beta oxidation are required to fully convert it to acetyl-CoA?

Accepted Answer

7

Question 9

Which of the following is NOT a direct inhibitor of pyruvate dehydrogenase?

Accepted Answer

High levels of AMP

Question 10

If a cell has high levels of NAD+, CoA, or AMP, what effect will this have on the conversion of pyruvate to acetyl-CoA?

Accepted Answer

It will speed up the conversion.

Question 11

Which of the following equations correctly represents the reaction catalyzed by phosphofructokinase in glycolysis?

Accepted Answer

$$\mathrm{F	ext{-}6	ext{-}P} + \mathrm{ATP} ightarrow \mathrm{F	ext{-}1,6	ext{-}P} + \mathrm{ADP}$$

Question 12

Which of the following best describes the role of beta oxidation in cellular respiration?

Accepted Answer

It breaks down fatty acids into two-carbon units that become acetyl-CoA.

Question 13

If a person is fasting and has low ATP levels, what is the expected effect on phosphofructokinase activity and glycolysis?

Accepted Answer

Phosphofructokinase activity will increase, speeding up glycolysis.

Question 14

Which of the following is a real-life consequence of a genetic mutation that causes phosphofructokinase to be insensitive to ATP inhibition?

Accepted Answer

Cells would continue glycolysis even when ATP is abundant, potentially leading to excessive lactic acid production.

Question 15

Which of the following best explains why the allosteric site of phosphofructokinase has a lower affinity for ATP than the active site?

Accepted Answer

To ensure that glycolysis is only inhibited when ATP levels are very high.

Question 16

In the citric acid cycle, what is the total ATP yield (including equivalents from NADH and FADH2) from one acetyl-CoA molecule?

Accepted Answer

$$1\ \mathrm{ATP} + 3\ \mathrm{NADH} 	imes 3\ \mathrm{ATP/NADH} + 1\ \mathrm{FADH}_2 	imes 2\ \mathrm{ATP/FADH}_2 = 12\ \mathrm{ATP}$$

Regulation of Cellular Respiration: Key Enzymes and Catabolic Pathways

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