This set of Protein Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Amino Acids – 1”.
1. Which of the following amino acid is acidic?
a) Asparagine
b) Leucine
c) Valine
d) Aspartic acid
View Answer
Explanation: Aspartic acid is the acidic amino acid among the given options. It contains an extra carboxyl group; hence it has acidic nature. It is negatively charged due do this extra carboxyl group. Aspartic acid and glutamic acid are the only two amino acids that are acidic.
2. What is the three-letter code of Glutamine?
a) Glu
b) Gly
c) Arg
d) Gln
View Answer
Explanation: The three-letter code for glutamine is Gln. Glutamine is a neutral and polar amino acid. Glu is the three-letter code for glutamine. Gly is the three-letter code for glycine. Arg is the three-letter code for arginine.
3. The three-letter code for threonine is ________
a) Tyr
b) Asn
c) Trp
d) Thr
View Answer
Explanation: The three-letter code for threonine is Thr. The three-letter codes for tyrosine, asparagine, and tryptophan are Tyr, Asn, and Trp respectively. Threonine is a neutral and polar amino acid.
4. Which among the following is the simplest amino acid?
a) Leucine
b) Alanine
c) Tryptophan
d) Glycine
View Answer
Explanation: Glycine is the simplest amino acid because it contains hydrogen atom as its side chain. Due to this hydrogen atom, the alpha carbon in glycine is achiral and glycine is optically inactive. Leucine, alanine, and tryptophan contain side-chain groups more complex and bigger than the hydrogen atom.
5. What is the one-letter code for tryptophan?
a) T
b) R
c) F
d) W
View Answer
Explanation: One-letter code for tryptophan is W. Tryptophan is a neutral and non-polar amino acid. It contains a benzene ring in its structure. T, R, and F are the one-letter codes for threonine, arginine, and phenylalanine respectively.
6. What is the one-letter code for glutamine?
a) G
b) L
c) E
d) Q
View Answer
Explanation: One-letter code for glutamine is Q. Glutamine is a neutral but polar amino acid. G, L, and E are the one-letter codes for glycine, leucine, and glutamine respectively.
7. What is the one-letter code for tyrosine?
a) T
b) E
c) R
d) Y
View Answer
Explanation: One-letter code for tyrosine is Y. Tyrosine is a neutral but polar amino acid. It contains a benzene ring and a hydroxyl group in its side chain. T, E, and R are the one-letter codes for threonine, glutamic acid, and arginine respectively.
8. What is the one-letter code for lysine?
a) L
b) Y
c) E
d) K
View Answer
Explanation: One-letter code for lysine is K. Lysine is a positively charged amino acid and it is basic. L, Y, and E are the one-letter codes for leucine, tyrosine, and glutamic acid respectively.
9. What is the one-letter code for aspartic acid?
a) A
b) S
c) T
d) D
View Answer
Explanation: One-letter code for aspartic acid is D. Aspartic acid is a negatively charged amino acid and it is acidic. A, S, and T are one-letter codes for alanine, serine, and threonine respectively.
10. Which among the following amino acids is not stable in the water?
a) Aspartic acid
b) Glutamic acid
c) Lysine
d) Leucine
View Answer
Explanation: Leucine is a neutral and non-polar amino acid, thus it has neither complete nor partial charge to interact with water molecules. Hence, it is not stable in water. Aspartic acid, glutamic acid, and lysine are charged amino acids, hence soluble in water.
11. Which of the following amino acids is likely to be soluble in water?
a) Leucine
b) Alanine
c) Glycine
d) Aspartic acid
View Answer
Explanation: Aspartic acid is a negatively charged amino acid. Thus, it has a negative charge to interact with water, hence it is likely to be soluble in water. Leucine, alanine, and glycine are neutral non-polar amino acids, therefore insoluble in water.
12. Proteins are made of _______
a) deoxyribonucleotides
b) ribonucleotides
c) glucopyranose
d) amino acids
View Answer
Explanation: Proteins are made of amino acids. Amino acids are structural monomers of proteins. There are around 20 standard amino acids in nature. Deoxyribonucleotides are the monomers of DNA. Ribonucleotides are the monomers of RNA. Glucopyranose is a monomer of few polysaccharides.
13. Amino acids are also known as ‘dipolar ions’ or ‘zwitterions’.
a) False
b) True
View Answer
Explanation: At physiological pH, the amino group present in amino acids is protonated, whereas the carboxyl group is deprotonated. This forms two charges (one positive and one negative) within an amino acid. Therefore, amino acids are also known as ‘dipolar ions’ or ‘zwitterions’.
14. The common amino acids are also called as alpha-amino acids because they contain their amino group attached to the alpha carbon.
a) False
b) True
View Answer
Explanation: The carbon next to carbonyl carbon in amino acids is called as alpha carbon. This alpha carbon contains an amino group as a substituent. Hence, the statement is true.
15. William C. Rose discovered the twentieth amino acid. Which amino acid is that?
a) Tyrosine
b) Tryptophan
c) Serine
d) Threonine
View Answer
Explanation: William C. Rose discovered the last and twentieth amino acid, threonine. Rose wanted to identify the nutritional content of individual amino acids. Out of the 20 amino acids, 10 are nutritionally essential. The other 10 amino acids are considered “dispensable”.
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