What Do You Know About Gluconeogenesis? Trivia Quiz
What do you know about gluconeogenesis? The brain needs energy to operate and the main source for this energy is found in glucose which we consume from other foods. Glucose is produced when the food is broken down. Do take up this quiz and see what you know about how glucose is produced and using which enzymes. All the best and see what new facts you might learn in the process.
- 1.
Gluconeogenesis is the production of glucose from non-carbohydrate molecules. Which of the following is not substrate for gluconeogenesis?
- A.
Lactate
- B.
Alanine
- C.
Glycerol
- D.
Acetly CoA
Correct Answer
D. Acetly CoAExplanation
Because it can't be converted back to pyruvate or any other molecule that can be used in gluconeogenesis.Rate this question:
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- 2.
Gluconeogenesis occurs in the liver and kidney. Which is of the following enzymes are important for gluconeogenesis are expressed exclusively in these tissues?
- A.
Glucose-6-phosphatase
- B.
Fructose-1,6-Bisphosphatase
- C.
Phosphoenol pyruvate carboxykinase
- D.
Pyruvate carboxylase
Correct Answer
A. Glucose-6-pHospHataseExplanation
Because this enzyme can be found only in these tissues where is missing from the muscles, so muscles can't release free glucose during gluconeogenesis.Rate this question:
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- 3.
Which of the following enzymes is not directly involved in gluconeogenesis?
- A.
Fructose-1,6-bisphosphatase
- B.
Pyruvate carboxylase
- C.
Hexokinase
- D.
Phosphoenolpyruvate carboxykinase (PEPCK)
Correct Answer
C. HexokinaseExplanation
Hexokinase is involved in glycolysis, where it phosphorylates glucose to form glucose-6-phosphate, initiating glucose breakdown for energy. It is not involved in gluconeogenesis, which synthesizes glucose from non-carbohydrate sources. In contrast, enzymes like Fructose-1,6-bisphosphatase, Pyruvate carboxylase, and Phosphoenolpyruvate carboxykinase (PEPCK) play critical roles in gluconeogenesis, facilitating various steps to produce glucose.Rate this question:
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- 4.
During gluconeogenesis, the three irreversible steps of glycolysis have to be bypassed. The final step is the conversion of glucose-6-P to glucose that is catalyzed by glucose-6-phosphatase. Which of the following statement is true about the reaction step?
- A.
Conversion of glucose-6-phosphate to glucose releases one ATP molecule
- B.
It is highly active enzyme in skeletal muscle
- C.
Defect in glucose-6-phosphatase leads to abnormal accumulation of glycogen in liver
- D.
The reaction occurs in mitochondria
Correct Answer
C. Defect in glucose-6-pHospHatase leads to abnormal accumulation of glycogen in liverExplanation
Because any defect in this enzyme could lead to accumulation of glycogen in the liver that because the glucose 6-phosphate can't be converted to g-1-pRate this question:
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- 5.
During prolonged starvation, which of the following hormone is responsible for increasing gluconeogenesis in the liver.
- A.
Insulin
- B.
Glucogon
- C.
TSH
- D.
Thyroxine
Correct Answer
B. Glucogon -
- 6.
Which of the following statements about gluconeogenesis is correct?
- A.
Muscles have a large glycogen store which gives rise to blood glucose during prolonged starvation.
- B.
Fatty acids are plentiful in the blood during starvation and are used for glucose synthesis.
- C.
The enzyme glucose-6-phosphatase hydrolyses glucose-6-phosphate and is present in most cells.
- D.
Gluconeogenesis enables the liver to maintain blood glucose levels during starvation
Correct Answer
D. Gluconeogenesis enables the liver to maintain blood glucose levels during starvationExplanation
The liver maintains blood glucose levels by breaking down its glycogen stores to release glucose into the blood but liver glycogen stores are exhausted after 24 hours of fasting. The brain and other cells such as red blood cells must have a constant supply of glucose to function normally. Unlike most other tissues these cells cannot use fatty acids. Fatty acids cannot penetrate the blood-brain barrier; red blood cells lack mitochondria and cannot metabolize them. Gluconeogenesis is the production of glucose. It occurs in the liver in starvation. Glucose is released from glucose-6-phosphate by the enzyme glucose-6-phosphatase. Only liver and kidney have this enzyme though because of its small mass the latter is relatively insignificant in this respect. Amino acids released from muscle protein breakdown are the main source of carbon atoms for gluconeogenesis.Rate this question:
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- 7.
Which of the following statements about the use and synthesis of glucose in the body is correct
- A.
Brain can use fatty acids for all its energy needs.
- B.
Red blood cells can use fatty acids for all their energy needs.
- C.
The brain can use ketone bodies for all its energy needs.
- D.
The brain can use glucose for all its energy needs.
Correct Answer
D. The brain can use glucose for all its energy needs.Explanation
Glucose is essential for the brain, kidney medulla, red blood cells, retinal cells and any other cells without mitochondria. It cannot be made from acetyl-CoA, and can only be made from any molecule that can be converted to pyruvate. The brain needs a constant supply of glucose to function normally. Fatty acids are unable to be used as a fuel source by the brain since they cannot cross the blood-brain barrier (they are reversibly bound to albumin in the circulation). Ketone bodies can be used as a proportion (40%) of the brain's fuel source, but it still requires a continual supply of glucose. Cells without mitochondria cannot use ketone bodies as fuel.Rate this question:
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- 8.
Which of the following statements about the process of gluconeogenesis is correct?
- A.
In gluconeogenesis, pyruvate is first converted to phosphoenolpyruvate by phosphoenolpyruvate carboxykinase.
- B.
In gluconeogenesis fructose-1:6-bisphosphatase converts fructose-1:6-bisphosphate into fructose-1-phosphate.
- C.
Glucose-6-phosphatase hydrolyses glucose-6-phosphate to release glucose into the blood.
- D.
Glucose-6-phosphatase hydrolyses glucose-6-phosphate and is found in liver and muscle.
Correct Answer
C. Glucose-6-pHospHatase hydrolyses glucose-6-pHospHate to release glucose into the blood.Explanation
Gluconeogenesis involves a reversal of several glycolytic reactions but there are three reactions that need to be bypassed because of thermodynamic considerations which make them irreversible. These are; the phosphorylation of glucose to glucose-6-phosphate using ATP, the phosphorylation of fructose-6-phosphate to fructose-1:6-bisphosphate, again with ATP. The third is the conversion of phosphoenolpyruvate (PEP) to pyruvate using pyruvate kinase. This forms ATP. In gluconeogenesis, pyruvate is first converted into oxaloacetate by the ATP-dependent pyruvate carboxylase reaction. This is then converted into PEP by PEP carboxykinase using GTP. The PEP is converted to fructose-1:6-bisphosphate then hydrolyzed by fructose-1:6-bisphosphatase. Glucose-6-phosphate is hydrolyzed by glucose-6-phosphatase to release glucose into the blood.Rate this question:
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- 9.
Which of the following statements about the sources of pyruvate used by the liver for gluconeogenesis is correct?
- A.
The main source of glucose carbons for gluconeogenesis is pyruvate synthesised from acetyl-CoA.
- B.
The main source of glucose carbons for gluconeogenesis is alanine derived from breakdown of muscle proteins.
- C.
The main source of glucose carbons cannot occur from muscles as they do not undergo gluconeogenesis.
- D.
The main source of glucose carbons in gluconeogenesis is pyruvate released from muscles
Correct Answer
B. The main source of glucose carbons for gluconeogenesis is alanine derived from breakdown of muscle proteins.Explanation
The main source of pyruvate used by the liver for gluconeogenesis is from the breakdown of muscle proteins promoted by the stress hormone cortisol. Several amino acids give rise to citric acid cycle acids and are converted to oxaloacetate. Pyruvate is converted to oxaloacetate by pyruvate carboxylase then to phosphoenolpyruvate by phosphoenolpyruvate carboxykinase. In muscles pyruvate accepts amino groups (from other amino acids), to form alanine which is released into the blood. In the liver, it is converted back to pyruvate for gluconeogenesis.Rate this question:
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- 10.
Which of the following statements about the effect of ethanol metabolism on gluconeogenesis is correct?
- A.
The metabolism of ethanol by the liver decreases the NADH/NAD+ ratio reducing its ability to perform gluconeogenesis.
- B.
The reduction of ethanol by the liver increases the NADH/NAD+ ratio reducing its ability to perform gluconeogenesis.
- C.
The oxidation of ethanol by the liver increases the NADH/NAD+ ratio increasing its ability to perform gluconeogenesis.
- D.
The metabolism of ethanol by the liver increases the NADH/NAD+ ratio reducing its ability to perform gluconeogenesis.
Correct Answer
D. The metabolism of ethanol by the liver increases the NADH/NAD+ ratio reducing its ability to perform gluconeogenesis.Explanation
Ethanol is oxidized to acetaldehyde in the liver cytoplasm by alcohol dehydrogenase. This is oxidized to acetate by acetaldehyde dehydrogenase in the mitochondria. Two NADH molecules are produced in the liver cell from each ethanol molecule. Intake of large amounts of alcohol results in the cellular NADH/NAD+ ratio is increased. Several dehydrogenases such as lactate dehydrogenase can be inhibited by this so that the pyruvate/lactate equilibrium is disturbed resulting in reduced amounts of pyruvate available for gluconeogenesis. Excessive drinking often results in reduced food intake so that dietary sources of glucose diminish. This coupled with impaired gluconeogenesis can result in an inadequate supply of glucose to the brain in extreme cases with dangerous consequences.Rate this question:
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- 11.
Which of the following statements about gluconeogenesis is not correct?
- A.
Lactate from muscle vigorous muscle activity can be used as a carbon source in gluconeogenesis.
- B.
Glycerol from the hydrolysis of triacylglycerols is converted to glucose in gluconeogenesis.
- C.
Lactate from red blood cells can be used as a carbon source in gluconeogenesis.
- D.
Fatty acids from the hydrolysis of triacylglycerols can be used as a carbon source in gluconeogenesis.
Correct Answer
D. Fatty acids from the hydrolysis of triacylglycerols can be used as a carbon source in gluconeogenesis.Explanation
Fatty acids from the hydrolysis of triacylglycerols cannot be used as a carbon source in gluconeogenesis. Fatty acids are oxidized to acetyl-CoA, but the latter cannot be converted to pyruvate, so fatty acids cannot be converted to glucose. Lactate from muscle vigorous muscle activity can be used as a carbon source in gluconeogenesis. It travels via the blood to the liver where it is first converted to pyruvate by lactate dehydrogenase, then to glucose by gluconeogenesis. Glycerol from the hydrolysis of triacylglycerols in adipose cells travels to the liver and is converted to glucose in gluconeogenesis. The enzyme glycerol kinase converts glycerol to glycerol-3-phosphate. It enters the gluconeogenesis pathway via dihydroxyacetone phosphate. Red blood cells can only undergo anaerobic glycolysis since they have no mitochondria so they produce lactate. The lactate travels to the liver where it is converted to pyruvate and is used as a carbon source in gluconeogenesis.Rate this question:
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- 12.
Which of the following statements regarding the general principles of glucose metabolism are correct?
- A.
Gluconeogenesis is the formation of glucose from glycogen.
- B.
Glucose may be stored as glycogen or converted to fat.
- C.
Glycogenolysis and gluconeogenesis are functions of the liver.
- D.
Gluconeogenesis is stimulated when plasma glucose is low.
- E.
Glycogenesis is stimulated when cellular ATP reserves are low.
Correct Answer(s)
B. Glucose may be stored as glycogen or converted to fat.
C. Glycogenolysis and gluconeogenesis are functions of the liver.
D. Gluconeogenesis is stimulated when plasma glucose is low.Explanation
When plasma glucose levels are high and cellular ATP reserves are adequate, glucose is stored in the form of glycogen or is converted to triglyceride. When plasma glucose levels fall, glycogen is broken down (glycogenolysis) to liberate glucose and glucose is synthesized from non-carbohydrate precursors (gluconeogenesis). The liver carries out both these processes.Rate this question:
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- 13.
Gluconeogenesis is often associated with
- A.
Ketosis
- B.
Hexoses
- C.
Pentoses
- D.
None of above
Correct Answer
A. KetosisExplanation
In gluconeogenesis, the fatty acid breakdown increase will increase the amount of Acetyl Co-A and some of Acetyl Co-A will be converted to ketone bodies.Rate this question:
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- 14.
Number of enzyme catalyzed reactions in gluconeogenesis are
- A.
12
- B.
11
- C.
13
- D.
10
Correct Answer
B. 11 -
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Jun 12, 2024Quiz Edited by
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Jul 04, 2016Quiz Created by
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