What joins amino acids to make proteins?

water molecule

Explanation:

Within a protein, multiple amino acids are linked together by peptide bonds, thereby forming a long chain. Peptide bonds are formed by a biochemical reaction that extracts a water molecule as it joins the amino group of one amino acid to the carboxyl group of a neighboring amino acid.

Answer: Peptide bonds

Explanation: A peptide bond is a bond in which two amino acid molecules are covalently joined together. The reaction involves the removal of water molecule from alpha carboxyl group of one amino acid and alpha amino group of another amino acid to form a peptide bond. When many amino acids are joined by peptide bond, the product is a polypeptide or protein.