Multiple Choice
In a standard amino acid, what does the R group represent?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
In a standard amino acid (the building block of proteins), which set of functional groups is always present in the backbone structure?
A
An aldehyde group and a hydroxyl group
B
A ketone group and a sulfhydryl group
C
An amino group and a carboxyl group
D
A phosphate group and a methyl group
Verified step by step guidance1
Understand that the backbone structure of a standard amino acid consists of a central carbon atom (called the alpha carbon) bonded to specific functional groups.
Recall that every standard amino acid has an amino group (–NH\_2) attached to the alpha carbon, which acts as a base and can accept a proton.
Recognize that every standard amino acid also has a carboxyl group (–COOH) attached to the alpha carbon, which acts as an acid and can donate a proton.
Note that other groups like aldehyde, ketone, sulfhydryl, phosphate, or methyl groups are not part of the consistent backbone structure but may be present in side chains or other biomolecules.
Conclude that the amino group and carboxyl group are the functional groups always present in the backbone of standard amino acids.
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