Analysis of a hexapeptide using enzymatic cleavage reveals the following result:
• Amino acid composition of the peptide is: 2R, A, V, S, Y
• Trypsin digestion yields two fragments and the compositions are: (R, A, V) and (R, S, Y)
• Chymotrypsin digestion yields two fragments and the compositions are: (A, R, V, Y) and (R, S)
• Digestion with carboxypeptidase A yields no cleavage product.
Given: Trypsin cleaves at carboxyl side of R. Chymotrypsin cleaves at carboxyl side of Y. Carboxypeptidase A cleaves at amino side of the C-terminal amino acid (except R and K) of the peptide.
The correct amino acid sequence of the peptide is:
A. RSYRVA
B. AVRYSR
C. SRYVAR
D. SVRRYA
Answer: Option B
Which one of the following is INCORRECT about protein structures?
A. A protein fold is stabilized by favorable noncovalent interactions
B. All parts of a fold can be classified as helices, strands or turns
C. Two non-covalent atoms cannot be closer than the sum of their van der Waals radii
D. The peptide bond is nearly planar
Which one of the following amino acids has three ionizable groups?
A. Glycine
B. Leucine
C. Valine
D. Lysine
During lactic acid fermentation, net yield of ATP and NADH per mole of glucose is
A. 2 ATP and 2 NADH
B. 2 ATP and 0 NADH
C. 4 ATP and 2 NADH
D. 4 ATP and 0 NADH
The reactions leading to the formation of amino acids from the TCA cycle intermediates are
A. Carboxylation
B. Isomerization
C. Transamination
D. Decarboxylation
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