Final answer:
To locate the α-carbon in an amino acid, look between the carboxyl and amino groups on the peptide backbone. The α-carbon is also the attachment point for the side chain that defines the identity of the amino acid. In a tripeptide, the last amino acid's free carboxyl group denotes the C-terminus of the chain.
Step-by-step explanation:
Identifying the α-Carbon in Amino Acids
In amino acids, the α-carbon is the central asymmetric carbon to which an amino group (N-H), a carboxyl group (C=O), a hydrogen atom, and a unique side chain (R group) are attached. When examining a tripeptide, identifying the α-carbon is straightforward as it lies between the carboxyl group and the amino group within the backbone of the peptide. Additionally, the side chain specific to each amino acid is connected to the α-carbon. In a glycine amino acid, for example, the side chain consists of a simple hydrogen atom. The α-carbon is crucial as it's the attachment point for the side chain that differentiates one amino acid from another in a protein's structure.
An amino acid with a free carboxylate group (-COO⁻) on one end is referred to as the C-terminus. In a given tripeptide, the last amino acid with the free carboxylate group is considered the C-terminus, such as lysine. The sequence of amino acids is typically written starting with the free amine group (N-terminus) and ending with the free carboxyl group (C-terminus), denoted in the sequence Gly-Trp-Ala, for example.
Regarding the strength of attractive interactions between pairs of amino acids, factors such as side-chain polarity, size, and capability to form hydrogen bonds or ionic interactions will influence the interaction strength. When predicting those interactions, the properties of the α-carbon's attached R groups will largely determine the relative strength of these interactions.
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