Multiple Choice
In proteins, what structural feature primarily differentiates one amino acid from another?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
In a standard amino acid, which functional group is always acidic (able to donate a proton) under typical aqueous conditions?
A
The side chain (R group)
B
The carboxyl group ()
C
The alpha carbon ()
D
The amino group ()
Verified step by step guidance1
Identify the main functional groups present in a standard amino acid: the amino group (−NH₂), the carboxyl group (−COOH), the alpha carbon (−CH), and the side chain (R group).
Recall the acid-base properties of these groups under typical aqueous conditions (around neutral pH). The carboxyl group (−COOH) can lose a proton (H⁺), making it acidic.
Understand that the amino group (−NH₂) generally acts as a base because it can accept a proton rather than donate one under physiological pH.
Recognize that the alpha carbon (−CH) is not acidic; it is a carbon atom bonded to hydrogen and does not typically donate protons.
Note that the side chain (R group) varies among amino acids and may or may not be acidic, but the carboxyl group is always acidic in standard amino acids.
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