Multiple Choice
In proteins, each amino acid differs from another primarily in which structural component?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
In all standard amino acids, which functional groups are always present on the alpha carbon (in their non-modified form)?
A
An aldehyde group and a ketone group
B
An alpha-amino group and an alpha-carboxyl group
C
A phosphate group and a sulfate group
D
A thiol group and a phenyl group
Verified step by step guidance1
Recall the general structure of standard amino acids: each has a central alpha carbon (Cα) bonded to four different groups.
Identify the four groups attached to the alpha carbon: an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a distinctive side chain (R group) that varies among amino acids.
Understand that the amino group attached to the alpha carbon is called the alpha-amino group, and the carboxyl group attached to the same carbon is called the alpha-carboxyl group.
Recognize that other groups mentioned (aldehyde, ketone, phosphate, sulfate, thiol, phenyl) are not universally present on the alpha carbon of all standard amino acids; some may appear in side chains but not as part of the core alpha carbon structure.
Conclude that the functional groups always present on the alpha carbon of all standard amino acids in their non-modified form are the alpha-amino group and the alpha-carboxyl group.
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