In the general structure of an amino acid, what does the R group represent?

In all standard amino acids, which functional groups are always present on the alpha carbon (in their non-modified form)?

In the context of amino acid structure, what primarily makes each of the 20 standard amino acids unique?

In biochemistry, what is the monomer unit of a protein called?

In a standard amino acid, what does the R group represent?

In proteinogenic amino acids, what primarily distinguishes one amino acid from another?

In proteins, what structural feature primarily differentiates one amino acid from another?

In a standard amino acid (the building block of proteins), which set of functional groups is always present in the backbone structure?

In proteins, what structural feature primarily makes one amino acid different from another?