Multiple Choice
In all standard amino acids, which functional groups are always present on the alpha carbon (in their non-modified form)?
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3. Amino Acids
Amino Acid Groups
Multiple Choice
In the general structure of an amino acid, what does the R group represent?
A
The alpha carbon that is always achiral in amino acids
B
The variable side chain that differs among amino acids and largely determines their chemical properties
C
The carboxyl group that is typically deprotonated as at physiological pH
D
The amino group that is typically protonated as at physiological pH
Verified step by step guidance1
Understand that the general structure of an amino acid consists of a central alpha carbon (Cα) bonded to four different groups: an amino group (−NH₃⁺), a carboxyl group (−CO₂⁻), a hydrogen atom, and an R group.
Recognize that the alpha carbon is typically chiral (except in glycine), meaning it has four different substituents, which is important for the stereochemistry of amino acids.
Identify the amino group (−NH₃⁺) as the nitrogen-containing group that is usually protonated at physiological pH, contributing to the amino acid's basic properties.
Identify the carboxyl group (−CO₂⁻) as the acidic group that is typically deprotonated at physiological pH, contributing to the amino acid's acidic properties.
Understand that the R group represents the variable side chain attached to the alpha carbon, which differs among amino acids and largely determines their unique chemical properties and behavior.
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