Final answer:
In biochemistry, the α-carbon of an amino acid is designated as the central, asymmetric carbon to which an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a side chain (R group) are attached. This R group varies for different amino acids, determining their unique properties and function in proteins. Except for glycine, the α-carbon is chiral due to being bound to four different groups.
Step-by-step explanation:
To designate the carbons in an amino acid biochemically, we focus on the α-carbon, which is the central, asymmetric carbon atom in the amino acid structure. The α-carbon is covalently bonded to an amino group (-NH₂), a carboxylic acid group (-COOH), a hydrogen atom (H), and a side chain, often denoted as the 'R group'. This R group is what differentiates one amino acid from another, and except for glycine, the α-carbon is bound to four different groups, making most amino acids chiral and optically active.
The designation of the α-carbon is essential as it helps in understanding the structure and properties of amino acids and the proteins they form. For instance, when looking at a Fisher projection representation, the carboxylic acid group (-COOH) is typically placed on top, and the amino group (-NH₂) will be on the left or right side. Except for glycine which has two hydrogen atoms attached to the α-carbon, making it non-chiral, the 19 other standard amino acids have a unique side chain connected to the α-carbon, providing a distinct three-dimensional structure that influences the protein's characteristics and function.