This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Amino Acid Metabolism”.
1. Which of the following is non-essential amino acid?
a) Lysine
b) Leucine
c) Serine
d) Methionine
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Explanation: Non-essential amino acids are those which are produced by the body and need not be supplied in the diet while essential amino acids are not produced in the body so these must be the part of the diet.
2. Which of these amino acids are essential for infants?
a) Methionine
b) Arginine and Histidine
c) Valine
d) Lysine and Leucine
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Explanation: Only arginine and histidine are considered essential for infants as arginine is required for proper growth and development while histidine provides inflammatory response and the production of hydrochloric acid in the stomach. These are not produced in the body and must be supplemented in the diet.
3. In which form the nitrogen is incorporated into an amino acid?
a) Nitrite
b) Glutamate
c) Nitrate
d) Ammonium ion
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Explanation: Source of nitrogen in all amino acid is ammonium ion. It is the key component of amino acids. The ammonium ion is first incorporated in amino acids and then in other biomolecules.
4. Transamination reaction in amino acid synthesis is catalyzed by enzyme_________
a) Nitric oxide synthase
b) Decarboxylase
c) Aminotransferase
d) Glutamate decarboxylase
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Explanation: Transamination is the reaction of an amino acid biosynthetic pathway in which α-amino group from one amino acid is transferred to an α-keto acid and produce new amino acid. This reaction is catalyzed by aminotransferases also known as transaminases.
5. Intermediates of which of the following metabolic pathway have not been used in the synthesis of amino acids?
a) Glycolysis
b) Fatty acid biosynthesis
c) Citric acid cycle
d) Pentose phosphate pathway
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Explanation: All amino acids are derived from the intermediates of metabolic pathways like glycolysis, citric acid cycle, and the pentose phosphate pathway. 20 amino acids have been divided into 6 families on the basis of the primary carbon source of each amino acid.
6. Name the amino acid which does not take part in transamination during amino acid catabolism.
a) Proline
b) Threonine
c) Lysine
d) Serine
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Explanation: Except serine rest three amino acids i.e. proline, threonine, and lysine take part in transamination during amino acid catabolism. Amino group donor is specific and called aminotransferase while acceptor is almost always α-ketoglutarate.
7. Name those living organisms which secrete nitrogen in the form of urea?
a) Ureotelic
b) Uricotelic
c) Ammonotelic
d) Nitroso compounds
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Explanation: All living organisms excrete nitrogen in three ways i.e. ureotelic which excrete in the form of urea; ammonotelic emit nitrogen in the form of ammonia, and uricotelic excrete uric acid.
8. The urea cycle is also referred to as Krebs-Henseleit cycle.
a) True
b) False
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Explanation: Urea cycle was discovered by Krebs and Henseleit, so, it is also known as Krebs-Henseleit cycle. The urea cycle is formed by aspartate, Co2, and ammonia in the cyclic pathway.
9. Name the type of cell in which synthesis of urea cycle takes place?
a) Pancreatic cell
b) Hepatocyte
c) Bowman’s gland cell
d) Urinary epithelium cell
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Explanation: Hepatocytes are liver cells in which urea synthesis take place in five enzymatic reactions, first two reactions occur in mitochondria while the rest three reactions take place in the cytosol.
10. Which of these is a hereditary disease caused due to an error in amino acid metabolism?
a) Homocystinuria
b) Albinism
c) Phenylketonuria
d) Branched-chain ketoaciduria
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Explanation: Phenylketonuria is a hereditary disorder caused by defective amino acid metabolism in which phenylalanine is not converted to tyrosine and deposited in the body. It is caused due to deficiency of enzyme phenylalanine hydroxylase.
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