Amino Acids and Proteins Multiple Questions and Answers.
Exercise Questions ::
Amino Acids and Proteins
1. Identify the amino acids containing nonpolar, aliphatic R groups ?
A. Phenylalanine, tyrosine, and tryptophan B. Glycine, alanine, leucine C. Lysine, arginine, histidine D. Serine, threonine, cysteine
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Answer: Option B
Explanation:
Glycine: H3 N+ – CH2 – COO– Alanine: H3 N+ – CH(CH3 ) – COO– Leucine: H3 N+ – CH(C4 H9 ) – COO– .
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2. The two amino acids having R groups with a negative net charge at pH 7.0 are ?
A. Aspartate and glutamate B. Arginine and histidine C. Cysteine and methionine D. Proline and valine
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Answer: Option A
Explanation:
Aspartate: H3 N+ – CH( CH2 COO– ) – COO– Glutamate: H3 N+ – CH( C2 H4 COO– ) – COO– .
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Answer: Option B
Explanation:
pI = 1 ⁄2 (pK1 + pK2 ) = 1 ⁄2 (2.34 + 9.60) = 5.97.
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4. Which of the following is a true statement ?
A. Tryptophan and tyrosine are significantly more polar than phenylalanine B. Leucine is commonly used as an ingredient in the buffers of SDS page C. Aspartate is an essential amino acid D. Lysine is a non-essential amino acid
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Answer: Option A
Explanation:
Tryptophan and tyrosine are significantly more polar than phenylalanine because of the tyrosine hydroxyl group and the nitrogen of the tryptophan indole ring.
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Answer: Option A
Explanation:
Serine is one of the 11 non-essential amino acids.
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