Multiple Choice
How many different standard amino acids are found in proteins?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
Amino acids are classified as acids because they always possess which functional group?
A
Sulfhydryl group (\(-SH\))
B
Amino group (\(-NH_2\))
C
Carboxyl group (\(-COOH\))
D
Hydroxyl group (\(-OH\))
Verified step by step guidance1
Understand the classification of amino acids: Amino acids are organic molecules that serve as the building blocks of proteins. They are classified as acids due to the presence of a specific functional group that can donate a proton (H⁺) in solution.
Identify the functional groups present in amino acids: Amino acids typically contain two key functional groups: an amino group (
) and a carboxyl group (
). Additional groups, such as sulfhydryl (
) or hydroxyl (
), may be present in the side chains of specific amino acids.
Focus on the carboxyl group (
): This group is acidic because it can release a proton (H⁺) into solution, forming a negatively charged carboxylate ion (
). This property is what classifies amino acids as acids.
Compare the other functional groups: The amino group (
) is basic, as it can accept a proton. The sulfhydryl group (
) and hydroxyl group (
) are not inherently acidic in the context of amino acids.
Conclude that the carboxyl group (
) is responsible for the acidic classification of amino acids, as it is the functional group that can donate a proton in solution.
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