Final answer:
Proteins can be denatured by extreme heat or extreme pH. Denaturation is a change in the structure of a protein that causes it to lose its functional shape and no longer perform its job.
Step-by-step explanation:
Proteins can be denatured by extreme heat or extreme pH. Denaturation is a change in the structure of a protein that causes it to lose its functional shape and no longer perform its job. For example, when milk curdles due to the addition of acidic lemon juice, the proteins in the milk are denatured. Denaturation can also occur in other substances such as lipids, carbohydrates, and nucleic acids.