In standard genetically encoded proteins, how many different amino acids (protein monomers) are commonly used to build polypeptides?

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?

Which hormone is synthesized from a single amino acid residue (i.e., derived from one amino acid) rather than from a peptide chain?

In a standard amino acid, which functional group is always acidic (able to donate a proton) under typical aqueous conditions?

In amino acids, what structural feature primarily gives each amino acid its unique chemical properties?

Where in a protein would you most likely find the R group (side chain) of a hydrophobic amino acid?

What is a monomer of a protein called?