MCAT Amino Acids + Proteins (High Yield) questions and answers with solutions 2025

What are amino acids? - ANSWER building blocks of proteins What is the structure of amino acids? - ANSWER molecules that contain two functional groups: an amino group (-NH2 ) and a carboxyl group (-COOH). What are α-amino acids? - ANSWER amino acids in which the amino group and the carboxyl group are bonded to the same carbon: the α-carbon of the carboxylic acid. How can we determine where the alpha carbon is? - ANSWER the α-carbon is the central carbon of the amino acid; for carboxylic acids, the α-carbon is the carbon adjacent to the carboxyl carbon. A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH. Thus, an amino acid with a carboxyl functional group and a side group contain carboxylic acids. What groups are attached to the alpha carbon? - ANSWER amino and carboxyl groups, a hydrogen atom, and a side chain, also called an R group (4 groups in total). For most amino acids, the α-carbon is a ________________ center, as it has four different groups attached to it; The one exception is glycine, which has a hydrogen atom as its R group, making it _____________. - ANSWER chiral (or stereogenic); achiral. What are chiral centers? - ANSWER Chiral centers are tetrahedral atoms (usually carbons) that have four different substituents. All chiral amino acids used in eukaryotes are _____________. - ANSWER L-amino acids. All naturally occurring amino acids in eukaryotes—except for glycine—are optically active, and all are L-isomers. What about glycine? Glycine is the only amino acid which does not have a chiral carbon atom, so it does not form stereoisomers therefore will not have L or D configurations. Except for __________, all L-amino acids have an "___" absolute configu