What are the four levels of protein structure?

Proteins have four levels of structure, each showing how the protein is built and folded.

Here’s a explanation:

1. Primary structure:
   • It is the sequence of amino acids in a protein chain.
   • This sequence is like the letters in a word — it decides how the protein will fold and function.
2. Secondary structure:
   • The chain of amino acids folds or coils into patterns like:
     • Alpha helix (spiral shape)
     • Beta sheet (zigzag or folded shape)
   • These shapes are held together by hydrogen bonds.
3. Tertiary structure:
   • The whole chain folds into a 3D shape.
   • It’s formed by interactions between amino acid side groups (like hydrogen bonds, ionic bonds, and disulfide bridges).
   • This shape decides the protein’s function.
4. Quaternary structure:
   • Some proteins have more than one chain.
   • These chains fit together to make one large, active protein.
   • Example: Hemoglobin has four protein chains.

In short:

• Primary: order of amino acids
• Secondary: local folding (helix or sheet)
• Tertiary: full 3D shape
• Quaternary: joining of multiple chains