Why are proteins water soluble and why do they become not water soluble after denaturation?
2 Answers
The solubility of a protein in water depends on the 3D shape of it. Usually globular proteins are soluble, while fibrous ones are not. Denaturation changes the 3D structure so the protein is not globular any more.
This has to do with the properties of the amino acids in the protein.
Explanation:
Proteins are buid up out of amino acids. All amino acids have a similar backbone structure, but differ in their side chains. These side chains have different properties, some are hydrophobic (not water soluble) whereas others are hydrophylic (water soluble).
To form a functional protein, the amino acid chain is folded in a way that the hydrophobic parts end up on the inside and the hydrophylic parts on the outside. This way a stable, water soluble protein is formed.
Denaturation changes the 3D shape of proteins and (parts) will unfold. This way some hydrophobic side chains, usually burried inside the protein, are exposed. The protein is then not soluble anymore.
