Gluconeogenesis- Multiple-choice questions

1)  A 4-month-old boy is being evaluated for seizures, psychomotor retardation, and hypotonia. Workup reveals elevated serum levels of lactate, alanine, pyruvate, and keto acids. Based on the clinical presentation, pyruvate carboxylase activity is measured using fibroblasts from a skin biopsy and is found to be markedly decreased. This enzyme is normally used to directly synthesize which of the following molecules?

a) Pyruvate

b) Oxaloacetate

c) Malate

d) Acetyl CoA

e) α- Ketoglutarate

2) A 34-year-old woman presents with central obesity, relatively thin extremities, and purple stria on her abdomen. Further, the workup reveals excessive serum cortisol and blood sugar levels of 258 mg/dl. Which of the following is the most likely cause of her hyperglycemia?

a) Excessive consumption of processed carbohydrates

b) A pancreatic adenoma secreting ACTH and glucagon

c) Cortisol-induced inhibition of insulin

d) Glucocorticoids cause induction of Phosphoenolpyruvate carboxy kinase gene

e) Increased gluconeogenesis due to increased provision of substrates through fatty acid oxidation.

3) A 56-year-old obese man complains of polydipsia, polyuria, and fatigue. A glucose tolerance test confirms the diagnosis of diabetes. He is placed on Metformin, which works by which of the following mechanisms?

a) Inhibiting hepatic gluconeogenesis

b) Increasing glucagon level

c) Increasing cellular responsiveness to circulating insulin

d) Stimulating the release or preformed insulin

e) Replacing the need for endogenous insulin

4) An enzyme used in both glycolysis and gluconeogenesis is:

a) 3-phosphoglycerate kinase.

b) glucose 6-phosphatase.

c) hexokinase.

d) phosphofructokinase-1.

e) pyruvate kinase.

5) Which one of the following statements about gluconeogenesis is false?

a) For starting materials, carbon skeletons derived from certain amino acids can be used.

b) It consists entirely of the reactions of glycolysis, operating in the reverse direction.

c) It employs the enzyme glucose 6-phosphatase.

d) It is one of the ways that mammals maintain normal blood glucose levels between meals.

e) It requires metabolic energy (ATP or GTP).

6) All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except:

a) 3-phosphoglycerate kinase.

b) Aldolase.

c) Enolase.

d) Phosphofructokinase-1.

e) Phosphohexoseisomerase.

7) In humans, gluconeogenesis:

a) can result in the conversion of protein into blood glucose.

b) helps to reduce blood glucose after a carbohydrate-rich meal.

c) is activated by the hormone insulin

d) is essential in the conversion of fatty acids to glucose.

e) requires the enzyme hexokinase.

8) Which of the following substrates cannot contribute to net gluconeogenesis in mammalian liver?

a) Alanine

b) Glutamate

c) Palmitate

d) Pyruvate

e) α-Keto glutarate.

9) A 6-year-old boy begins playing soccer in a community league. After his first game of the year, he is brought to see his pediatrician because of his severe muscle cramps and blood in his urine. He is subsequently found to be having deficiency of lactate dehydrogenase. This enzyme is important in which of the following conversions?

a) Pyruvate to Acetyl CoA

b) Pyruvate to Oxaloacetate

c) Pyruvate to Alanine

d) Pyruvate to Phosphoenol pyruvate

e) Pyruvate to lactate

10) A newborn infant is found to be having persistent hypoglycemia despite decreased feeding intervals. The child is also irritable with a moderate degree of hepatomegaly. He is found to have a normal level of muscle fructose 1,6 bisphosphatase but a decreased level of liver isoform. Which of the following statements is true of fructose 1,6 bisphosphatase?

a) It is induced by Adenosine monophosphate (AMP)

b) It is induced by Insulin

c) It is inhibited by Fructose 2,6 bisphosphate

d) It is induced in the fed state

e) It is inhibited during fasting.

11) A 14-year-old  high school girl who is extremely conscious about her appearance has gone a full day fasting to fit into a dress she intentionally brought a size smaller than her actual size for a dance party. Which of the following organs/tissues contributes to the glucose that is being synthesized through gluconeogenesis during periods of prolonged fasting?

a) Spleen

b) Red blood cells

c) Skeletal muscle

d) Liver

e) Brain

12) An 8 -year-old boy presents with frequent episodes of weakness, accompanied by sweating and feelings of dizziness. Physical examination is remarkable for palpably enlarged liver and kidneys. Blood biochemistry reveals lactic acidemia. The patient is diagnosed with a deficiency of glucose-6-phosphatase, which is normally only expressed in which of the following?

a) Liver and muscle

b) Liver and brain

c) Erythrocytes

d) Liver and adipose tissues

e) Liver and kidney.

13)  A 32-year-old bodybuilder has decided to go on a diet consisting of egg whites to ensure only proteins for muscle growth. After a few weeks, he experiences decreased energy and is found to be hypoglycemic. A nutritionist tells the patient that he most likely has a deficiency of vitamin Biotin. Which of the following enzymes cannot catalyze its step in synthesizing glucose from pyruvate?

a) Pyruvate carboxylase

b) Phosphoenol pyruvate carboxy kinase

c) Glucose 6-phosphatase

d) Fr 1,6 bisphosphatase

e) Phosphoglycerate kinase.

14) In an individual at rest who has fasted for 12 hours, which of the following occurs?

a) Gluconeogenesis is the major process by which blood glucose is maintained

b) Liver glycogen stores are depleted

c) Glycogen synthase is activated in the liver

d) Adenylate cyclase is inactivated in the liver

e) Phosphorylase, pyruvate kinase, and glycogen synthase are phosphorylated in the liver.

15) Which of the following is a common intermediate in converting glycerol and lactate to glucose?

a) Pyruvate

b) Oxaloacetate

c) Malate

d) Glucose 6-phosphate

e) Phosphoenolpyruvate.

16) In converting pyruvate to glucose during gluconeogenesis, which of the following is true?

a) Biotin is required

b) CO2 added in one reaction appears in the final product

c) Energy is used up in the form of GTP

d) All the reactions take place in the cytosol

e) PDH is the allosteric enzyme used.

17) Which of the following glycolytic enzymes is used in gluconeogenesis?

a) Glucokinase

b) Phosphofructokinase-1

c) Aldolase B

d) Phosphoglycerate kinase

e) Pyruvate kinase.

18) The conversion of pyruvate to fructose 1,6 bisphosphate by the gluconeogenic pathway involves which of the following?

a) Requires lactate dehydrogenase

b) Requires hexokinase

c) Produces 2 ATP and 2GTP

d) Requires 4 ATP and 2 GTP

e) Acetyl CoA is not required to activate this pathway.

19) A high ratio of insulin to glucagon can:

a) Promote gluconeogenesis

b) Promote glycogenolysis

c) Found in Type 1 Diabetes Mellitus

d) Occurs during a fasting state

e) Promotes synthesis of glycogen

20) Which of the following is a precursor for gluconeogenesis?

a) Glycogen

b) Glycerol

c) Glucagon

d) Galactose

e) Glucose 1- P.

Key to answers

1. b
2. d
3. a
4. a
5. b
6. d
7. a
8. c
9. e
10. c
11. d
12. e
13. a
14. e
15. d
16. a
17. d
18. d
19. e
20. b

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