This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Carbohydrate Metabolism”.
1. Name the pathway for glucose synthesis by non-carbohydrate precursors?
a) Glycogenesis
b) Glycolysis
c) Gluconeogenesis
d) Glycogenolysis
View Answer
Explanation: Synthesis of glucose from non-carbohydrate sources is carried out by gluconeogenesis. It is the universal pathway, found in all plants, animals, and microorganisms.
2. What is the site for gluconeogenesis?
a) Liver
b) Blood
c) Muscles
d) Brain
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Explanation: Gluconeogenesis in animals takes place in the liver as well as some extent in the kidney cortex. The kidney is capable of making glucose during the condition of starvation and can make up to 50% of glucose.
3. Which of the following is not the precursor of gluconeogenesis?
a) Glycolytic products
b) Citric acid cycle intermediates
c) Glucogenic amino acid
d) Lysine or leucine
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Explanation: Only leucine or lysine is the substrate which is not used for gluconeogenesis as these amino acids produce only acetyl-CoA upon degradation. Animals cannot carry out gluconeogenesis by two acetyl carbon of acetyl-CoA.
4. Name the enzyme which is responsible for the conversion of pyruvate to phosphoenolpyruvate (PEP)?
a) Pyruvate carboxylase
b) Pyruvate carboxykinase
c) Glucose 6-phosphatase
d) Phosphofructokinase
View Answer
Explanation: The conversion of pyruvate to PEP takes place in two stages, the first reaction is catalyzed by pyruvate carboxylase which converts pyruvate to oxaloacetate and in second reaction oxaloacetate is converted by pyruvate carboxykinase to PEP.
5. Gluconeogenesis is also carried out in muscle and brain.
a) True
b) False
View Answer
Explanation: Gluconeogenesis cannot be carried out in muscle and brain as they do not have glucose 6-phosphatase enzyme which is required to convert glucose 6-phosphate to glucose. Glucose 6-phosphatase can only be established in the endoplasmic reticulum of kidney and liver cells.
6. Which of the following are major sites for glycogen storage?
a) Adipose tissue
b) Bones
c) Muscle and liver
d) Kidney and liver
View Answer
Explanation: Glycogen is stored in muscle and liver only. The amount of glycogen is high in the liver but a larger amount of glycogen stored in the greater bunch of skeletal muscles. The liver uses its glycogen for the synthesis of glucose for all of the body while muscles use its glycogen for its own energy.
7. Which of the following is the precursor of glycogen?
a) Glycerol 3-phosphate
b) Malate
c) UDP-glucose
d) Leucine and lysine
View Answer
Explanation: Glucose 1-phosphate and uridine triphosphate work together to activate UDP-glucose which acts as a precursor of glycogen.
8. The priming function in glycogen synthesis is carried out by_________
a) Lysine
b) Arginine
c) Glycogenin
d) Glutamate
View Answer
Explanation: Glycogen synthesis is carried out with the help of a primer by its priming action. Glycogenin is a primer which adds glucosyl residue in the polypeptide chain that already has more than four residues.
9. Name the enzyme which is used for branching of glycogen?
a) Branching enzyme
b) Hexokinase
c) Phosphoglucomutase
d) Glycogen synthase
View Answer
Explanation: Branching enzyme is also known as amylo-1, 4 —–> 1, 6 transglycosylase which adds a branch at four residues away from the existing branch. Enzymes in hexokinase, phosphoglucomutase, and glycogen synthase are used in glycogen synthesis but not in branching.
10. Which of the following hormone maintain blood glucose level by activation of gluconeogenesis?
a) Nor-epinephrine
b) Glucagon
c) Insulin
d) Epinephrine
View Answer
Explanation: Glucagon acts opposite to insulin, and is secreted by the α-cells of the pancreatic islets. It maintains blood glucose level by the activation of glycogenolysis and gluconeogenesis.
11. Name the hormone which is secreted in an emergency or in stress condition?
a) Epinephrine
b) Glucagon
c) Insulin
d) Melanin
View Answer
Explanation: Epinephrine is also known as emergency hormone and it is secreted in the condition of stress and emergencies like injury, pain, fear, accident, and grief. It increases the level of sugar in the blood by stimulating glycogenolysis.
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