Multiple Choice
Which tryptophan (Trp) residue of carbonic anhydrase can be selectively modified with chloroform (CHCl$_3$) at 20\(^{\circ}\)C?
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3. Amino Acids
Amino Acid Groups
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In the amino acid shown here, which functional group is always present in all standard amino acids?
A
Hydroxyl group (\(-OH\))
B
Amino group (\(-NH_2\))
C
Phosphate group (\(-PO_4^{2-}\))
D
Methyl group (\(-CH_3\))
Verified step by step guidance1
Step 1: Begin by recalling the general structure of a standard amino acid. All amino acids share a common backbone consisting of a central carbon atom (the alpha carbon) bonded to four groups: an amino group (
), a carboxyl group (
), a hydrogen atom, and a variable side chain (R group).
Step 2: Analyze the functional groups listed in the problem. The hydroxyl group (
) is not universally present in all amino acids; it is specific to certain side chains, such as serine and threonine. Similarly, the phosphate group (
) and methyl group (
) are specific to certain amino acids and are not part of the universal structure.
Step 3: Focus on the amino group (
). This functional group is always present in all standard amino acids as part of the backbone structure. It is essential for the formation of peptide bonds during protein synthesis.
Step 4: Compare the amino group (
) with the other options provided. The amino group is the only functional group that is universally present in all standard amino acids, making it the correct answer.
Step 5: Conclude that the amino group (
) is the correct answer based on its universal presence in the structure of all standard amino acids.
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Amino Acid Groups practice set
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