Final answer:
Amino acids share a common structure with an alpha carbon bonded to an NH₂ group, COOH group, hydrogen atom, and a unique R group or side chain; the R group determines the properties and role within proteins.
Step-by-step explanation:
All amino acids have a fundamental structure in common, which includes a central alpha (α) carbon atom bonded to four different groups: an amino group (NH₂), a carboxyl group (COOH), a hydrogen atom, and a variable group known as the R group or side chain. This R group is what makes each of the 20 amino acids unique.
For instance, amino acids like valine are nonpolar, while others like lysine have positively charged side chains. Amino acids serve as monomers to create proteins, and they have excellent buffering capabilities due to containing both an acidic and a basic component, which helps regulate the body's acid-base balance.
The R group differs among amino acids, affecting their chemical properties and how proteins fold and function. For example, the R groups in cysteine and methionine contain sulfur, which impacts how these amino acids interact within a protein structure. These differences in the R groups are essential for the diversity of protein structures and functions in biological systems.