Structure of Proteins and Amino Acids

Amino Acids

• Proteins are composed of long chains of amino acids.
• Structure of Amino Acids
  • All amino acids have carboxyl and amino functional groups.
  • They possess a unique R group which determines their chemical properties.

Formation of Proteins

• Peptide Bonds
  • Amino acids are linked by peptide bonds to form polypeptide chains.

Levels of Protein Structure

1. Primary Structure
   • Sequence of amino acids in a polypeptide chain.
   • Analogous to letters in the alphabet; varying sequences form different proteins.
2. Secondary Structure
   • Formation of pleated sheets or helices.
   • Stabilized by hydrogen bonds and interactions between R groups of nearby amino acids.
3. Tertiary Structure
   • Refers to the overall 3D shape of a polypeptide.
   • Formed by folding and twisting of secondary structures.
   • Stabilized by various bonds and interactions between R groups on the chain.
   • Polypeptides with a tertiary structure are commonly referred to as proteins.
4. Quaternary Structure
   • Involves interactions between multiple protein molecules.
   • Results in large protein complexes.
   • Example: Hemoglobin and sodium channels in cell membranes.

---

• Proteins can be formed and differentiated by altering the number and sequence of 20 amino acids, similar to creating words with the alphabet.