To understand proteins, it is necessary to understand amino acids, to learn their structures and to learn a few of the functions and essentiality of the amino acids. It consists of two carbon atoms covalently bonded to each other. It is this carbon that makes all amino acids used by man the a -amino acids.
R groups are radical groups, representative groups or reactive groups.
In this case, and for the case of all the amino acids, we will use the second definition of R group to mean the rest of the amino acid molecule beyond the 2d carbon in the back bone of the amino acid. Gly's structure may be seen below, Figure 1 . The difference between ala and gly is the the H in gly has been replaced by a CH 3 in ala. Ala is a small amino acid, especially suited for diffusing from muscle cells into the blood to be transported by the blood to the liver for utilization in gluconeogenesis. Leu is the only purely ketogenic amino acid.