BIOCHEM CHAPTER 3 EXAM 4
The chirality of an amino acid results from the fact that its α carbon:
A) has no net charge.
B) is a carboxylic acid.
C) is bonded to four different chemical groups.
D) is in the L absolute configuration in naturally occurring proteins.
E) is symmetric. - CORRECT ANSWER-C) is bonded to four different chemical groups
Of the 20 standard amino acids, only ___________ is not optically active. The reason is
that its side chain ___________.
A) alanine; is a simple methyl group
B) glycine; is a hydrogen atom
C) glycine; is unbranched
D) lysine; contains only nitrogen
E) proline; forms a covalent bond with the amino group - CORRECT ANSWER-B)
Glycine; is a hydrogen atom
Two amino acids of the standard 20 contain sulfur atoms. They are:
A) cysteine and serine.
B) cysteine and threonine.
C) methionine and cysteine
D) methionine and serine
E) threonine and serine. - CORRECT ANSWER-C) methionine and cysteine
All of the amino acids that are found in proteins, except for proline, contain a(n):
A) amino group.
B) carbonyl group.
C) carboxyl group.
D) ester group.
E) thiol group. - CORRECT ANSWER-A) amino group
Which of the following statements about aromatic amino acids is correct?
A) All are strongly hydrophilic.
B) Histidine's ring structure results in its being categorized as aromatic or basic,
depending on pH.
C) On a molar basis, tryptophan absorbs more ultraviolet light than tyrosine.
D) The major contribution to the characteristic absorption of light at 280 nm by proteins
is the phenylalanine R group.
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