Biochemistry Multiple Choice Questions on “Coordinated Regulation of Glycolysis and Gluconeogenesis”.
1. Gluconeogenesis responds to which of the following?
A. Hormonal control
B. pH control
C. Temperature control
D. Blood control
Answer: A
Clarification: When the blood glucose level decreases, the hormone glucagon signals the liver to produce and release more glucose and to stop consuming it for its own needs. One source of glucose is gluconeogenesis.
2. When blood sugar levels fall, glycolysis is halted in liver to allow ___________
A. Homeostasis
B. Anaerobic respiration
C. Aerobic respiration
D. Gluconeogenesis
Answer: D
Clarification: Gluconeogenesis produces glucose in order to compensate the fall.
3. How many steps are catalyzed by the same enzymes in both glycolysis and gluconeogenesis?
A. 6
B. 7
C. 8
D. 9
Answer: B
Clarification: Phosphohexose isomerase, aldolase, triose phosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, phosphoglycerate mutase and enolase are the enzymes which catalyze the reactions in both glycolysis and gluconeogenesis.
4. How many steps are catalyzed by different enzymes in glycolysis and gluconeogenesis?
A. 2
B. 3
C. 4
D. 5
Answer: B
Clarification: Hexokinase, phosphofructokinase-1 and pyruvate kinase in glycolysis, Glucose 6-phosphatase, fructose 1, 6-bisphosphatase, PEP carboxykinase and pyruvate carboxylase in gluconeogenesis.
5. Three reactions of glycolysis are so exergonic, which are not catalyzed by?
A. Hexokinase
B. PFK-1
C. Pyruvate kinase
D. Pyruvate dehydrogenase
Answer: D
Clarification: Three glycolytic enzymes are subjected to allosteric regulation: hexokinase IV, PFK-1 and pyruvate kinase.
6. What are the effects of increased concentration of citrate?
A. Increases the inhibitory effect of ATP
B. Decreases the inhibitory effect of ATP
C. Increases the activity of ATP
D. Increases the activity of AMP
Answer: A
Clarification: Citrate is a key intermediate in the aerobic oxidation of pyruvate, fatty acids and amino acids. It serves as an allosteric regulator of PFK-1; its high concentration increases the inhibitory effect of ATP, further reducing the flow of glucose through glycolysis.
7. The second control point in gluconeogenesis is the reaction catalyzed by ___________
A. Pyruvate kinase
B. Pyruvate dehydrogenase
C. FBPase-1
D. PFK-1
Answer: C
Clarification: The second control point in gluconeogenesis is the reaction catalyzed by fructose 1, 6-bisphosphatase-1.
8. Which of the following statements is true about PFK-1?
A. It is stimulated by AMP and ADP
B. It is stimulated by citrate and ATP
C. It is inhibited by AMP and ADP
D. It is stimulated by citrate and ADP
Answer: A
Clarification: AMP promotes glycogen degradation and glycolysis by activating glycogen phosphorylase and stimulating the activity of phosphofructokinase-1. ATP and citrate are allosteric inhibitors.
9. Which of the following statements is true regarding acetyl co-A?
A. It stimulates pyruvate dehydrogenase
B. It stimulates pyruvate carboxylase
C. It inhibits pyruvate carboxylase
D. It stimulates hexokinase
Answer: B
Clarification: Gluconeogenesis is regulated at the level of pyruvate carboxylase which is activated by acetyl co-A.
10. Which of the following is a potent regulator of glycolysis and gluconeogenesis?
A. Fructose 2, 6-bisphosphate
B. Fructose 1, 6-bisphosphate
C. Fructose 6-phosphate
D. Glucose 1, 6-bisphosphate
Answer: A
Clarification: The hormonal regulation of glycolysis and gluconeogenesis is mediated by fructose 2, 6-bisphosphate.