Denaturation is the breaking of hydrogen bonds within a protein molecule that is responsible for the highly ordered structure of the protein in its natural state. During denaturation, the unique three-dimensional structure changes.
Due to changes in temperature, pH, or other chemical activities, denaturation of protein molecules occur.
In many situations, denaturation is reversible. Proteins can not regain their native structure until the denaturing agent is removed.
However, there can be some situations when denaturation is irreversible like the exposure of proteins to extreme heat.