The small molecule that links chemically to other amino acids to form proteins is called an amino acid.

Here's why:

* Proteins are polymers of amino acids: Proteins are large, complex molecules made up of long chains of amino acids.

* Amino acids are the monomers: Amino acids are the building blocks of proteins. They are small molecules with a central carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom (-H), and a side chain (R group).

* Peptide bonds: Amino acids link together through peptide bonds. This occurs when the carboxyl group of one amino acid reacts with the amino group of another amino acid, releasing water. This process is called dehydration synthesis.

So, the correct answer is amino acid.