Question 1

Which of the following best describes the primary function of NAD+ in cellular metabolism?

Accepted Answer

NAD+ serves as an electron carrier, accepting electrons during oxidation-reduction reactions.

Question 2

During glycolysis, ATP is both consumed and produced. At which steps is ATP consumed?

Accepted Answer

ATP is consumed during the conversion of glucose to glucose-6-phosphate and fructose-6-phosphate to fructose-1,6-bisphosphate.

Question 3

Which equation correctly represents the reduction of NAD+ to NADH?

Accepted Answer

$$\mathrm{NAD}^+ + 2\,e^- + 2\,H^+ \rightarrow \mathrm{NADH} + H^+$$

Question 4

In the absence of oxygen, what is the fate of pyruvate in skeletal muscle cells, and why is this process important?

Accepted Answer

Pyruvate is converted to lactate, regenerating NAD+ needed for glycolysis to continue.

Question 5

Which of the following statements about the Cori cycle is correct?

Accepted Answer

Lactate produced in muscles is transported to the liver, where it is converted back to glucose.

Question 6

Cancer cells are known to oxidize glucose at a much higher rate than normal cells. What is the primary reason for this increased glucose consumption?

Accepted Answer

Cancer cells use pyruvate for macromolecular synthesis rather than complete oxidation in the mitochondria.

Question 7

Which of the following best explains why ATP is both a substrate and a regulator in glycolysis?

Accepted Answer

ATP donates phosphate groups in early steps and inhibits phosphofructokinase when in excess.

Question 8

Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA in the mitochondrial matrix, and what type of reaction is this?

Accepted Answer

Pyruvate dehydrogenase complex; decarboxylation and oxidation

Question 9

Which of the following statements about mitochondrial DNA is correct?

Accepted Answer

Most mitochondrial proteins are encoded by nuclear DNA and synthesized in the cytosol.

Question 10

A patient with a genetic defect in the pyruvate symporter would most likely experience which of the following cellular consequences?

Accepted Answer

Reduced entry of pyruvate into mitochondria, leading to decreased aerobic ATP production.

Question 11

Which of the following best describes the role of allosteric regulation in glycolysis and gluconeogenesis?

Accepted Answer

Allosteric effectors modulate enzyme activity to coordinate energy needs, activating or inhibiting key enzymes.

Question 12

Which of the following carbohydrate substrates can enter glycolysis after conversion to an intermediate, and what is the significance of this process?

Accepted Answer

Galactose, which is converted to glucose-6-phosphate, allowing cells to utilize various dietary sugars for ATP production.

Question 13

Which of the following equations represents the net ATP yield from glycolysis per molecule of glucose?

Accepted Answer

$$\mathrm{Glucose} + 2\,\mathrm{ADP} + 2\,\mathrm{P_i} + 2\,\mathrm{NAD}^+ \rightarrow 2\,\mathrm{Pyruvate} + 2\,\mathrm{ATP} + 2\,\mathrm{NADH} + 2\,\mathrm{H}_2\mathrm{O}$$

Question 14

A mutation in the gene encoding phosphofructokinase (PFK) results in a loss of allosteric inhibition by ATP. What is the most likely metabolic consequence?

Accepted Answer

Glycolysis would proceed unchecked, potentially leading to excessive ATP and pyruvate production.

Question 15

Which of the following best explains why mitochondria are often called the 'powerhouse of the cell'?

Accepted Answer

They generate most of the cell's ATP through oxidative phosphorylation.

Question 16

Which of the following is a correct statement about the transport of mitochondrial matrix proteins?

Accepted Answer

Most mitochondrial matrix proteins are synthesized in the cytosol and imported post-translationally into the mitochondria.

Question 17

Which of the following best describes the role of porins in mitochondrial membranes?

Accepted Answer

Porins allow the passage of small molecules, such as pyruvate, across the outer mitochondrial membrane.

Question 18

A researcher uses electron microscopy to study mitochondria. What structural feature is most likely to be revealed by this technique?

Accepted Answer

The highly folded inner mitochondrial membrane (cristae).

NAD+/NADH Function and Glycolysis Regulation Study Guide

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