How are amino acids linked together to form proteins?

Amino acids are linked together to form proteins through peptide bonds.

Step-by-step process:

1. Amino acid structure:
   Each amino acid has:
   • An amino group (-NH₂)
   • A carboxyl group (-COOH)
   • A side chain (R group)
2. Peptide bond formation:
   • The carboxyl group of one amino acid reacts with the amino group of another.
   • A molecule of water (H₂O) is released in this condensation (dehydration) reaction.
   • The covalent bond formed between the carbon of the carboxyl group and the nitrogen of the amino group is called a peptide bond (-CO–NH-).
3. Formation of polypeptides:
   • When many amino acids join together through peptide bonds, they form a polypeptide chain.
   • Polypeptides fold into specific shapes to become functional proteins.

In short:
Amino acids are linked by peptide bonds in a condensation reaction, forming polypeptide chains, which fold to make proteins.