Question 1

Which of the following statements best describes the difference between catabolic and anabolic pathways in metabolism?

Accepted Answer

Catabolic pathways break down complex molecules to release energy, while anabolic pathways synthesize complex molecules from simple precursors.

Question 2

During glycolysis, which enzyme catalyzes the rate-limiting and committed step, and what is its most potent allosteric activator?

Accepted Answer

Phosphofructokinase-1 (PFK-1); Fructose 2,6-bisphosphate

Question 3

A patient presents with chronic, nonspherocytic hemolytic anemia. Laboratory tests reveal a deficiency in a glycolytic enzyme. Which enzyme deficiency is most likely responsible, and what is a possible evolutionary advantage of this condition?

Accepted Answer

Pyruvate kinase deficiency; resistance to malaria

Question 4

Which of the following best explains why glucose is phosphorylated upon entry into the cell?

Accepted Answer

Phosphorylation traps glucose inside the cell because glucose 6-phosphate cannot cross the membrane.

Question 5

In the cAMP second messenger system, which sequence of events occurs after a hormone binds to its G protein-coupled receptor (GPCR)?

Accepted Answer

Activation of adenylyl cyclase, increase in cAMP, activation of protein kinase A, phosphorylation of target proteins

Question 6

Which of the following equations correctly represents the net reaction of aerobic glycolysis?

Accepted Answer

$$\mathrm{Glucose} + 2\ \mathrm{NAD}^+ + 2\ \mathrm{ADP} + 2\ \mathrm{P_i} \rightarrow 2\ \mathrm{Pyruvate} + 2\ \mathrm{NADH} + 2\ \mathrm{H}^+ + 2\ \mathrm{ATP} + 2\ \mathrm{H_2O}$$

Question 7

Which of the following statements about hexokinase and glucokinase is TRUE?

Accepted Answer

Glucokinase has a high $$K_m$$ and is responsible for glucose phosphorylation during hyperglycemia.

Question 8

A patient is exposed to arsenate. Which step of glycolysis is most directly affected, and what is the consequence for ATP production?

Accepted Answer

Conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate; decreased net ATP production

Question 9

Which of the following best describes the role of 2,3-bisphosphoglycerate (2,3-BPG) in red blood cells?

Accepted Answer

It decreases the affinity of hemoglobin for oxygen, facilitating oxygen delivery to tissues.

Question 10

Which of the following is a direct consequence of elevated levels of glucagon in the liver?

Accepted Answer

Decreased levels of fructose 2,6-bisphosphate, inhibition of glycolysis, and stimulation of gluconeogenesis

Question 11

Which of the following transporters is responsible for sodium-dependent glucose cotransport in the intestinal epithelium?

Accepted Answer

SGLT (sodium-glucose linked transporter)

Question 12

During intense exercise, muscle cells produce lactate. What is the primary reason for this metabolic shift?

Accepted Answer

The oxidative capacity of the respiratory chain is exceeded, leading to an increased NADH/NAD$$^+$$ ratio and favoring reduction of pyruvate to lactate.

Question 13

Which of the following is NOT a fate of pyruvate in human metabolism?

Accepted Answer

Reduction to ethanol by pyruvate decarboxylase

Question 14

Which enzyme catalyzes the final irreversible step of glycolysis, and what is the product?

Accepted Answer

Pyruvate kinase; pyruvate

Question 15

Which of the following best describes substrate-level phosphorylation in glycolysis?

Accepted Answer

ATP is generated by the transfer of a phosphate group from a high-energy intermediate to ADP.

Question 16

Which of the following statements about the regulation of glycolysis in the liver is TRUE?

Accepted Answer

Insulin increases the transcription and synthesis of hexokinase, PFK-1, and pyruvate kinase.

Question 17

Which of the following best explains why lactic acidosis can occur during circulatory shock?

Accepted Answer

Impaired oxygen delivery leads to decreased oxidative phosphorylation, increased anaerobic glycolysis, and accumulation of lactic acid.

Question 18

Which of the following is TRUE regarding the fate of NADH produced during glycolysis under aerobic conditions?

Accepted Answer

NADH is reoxidized by the electron transport chain, producing ATP.

Introduction to Metabolism and Glycolysis: Biochemistry Study Notes

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