Question

---causes proteins to denature.
A. Water
B. Heat
C. Enzyme
D. Pressure

Answer 1

Hint: Proteins are held together by the help of covalent and hydrogen bonds. Denaturation disrupts the bond as a result of which the protein structure uncoils into random shape.

Complete Answer:
To solve this question, we must know about the causes of protein denaturation.
Denaturation is the process of changing of shape but retaining its chemical properties. It is an irreversible change in which the proteins get precipitated. The denaturation inactivates the protein.

The factors which causes denaturation of proteins are:
- Heat- Heating breaks the alpha and beta structure of protein as a result of which the physical properties of the protein gets altered. For example, boiling an egg. On boiling the egg changes from liquid to solid structure.
- By chemical action like presence of salts.
- By change in pH as it happens in curdling milk by adding acid.
- Vigorous agitation also disrupts the bonds like in beaten eggs.
- Exposure to UV radiations.
- Water does not cause denaturation of protein, rather it only causes dilution.
- Enzymes- All the enzymes do not cause denaturation. Only the peptidases can cause denaturation of proteins.

The correct answer is (B). Heat causes proteins to denature.

Note: Denaturation is an extreme process which is a chemical change which cannot be revered. The coagulated protein cannot regain its properties. The heating increases the kinetic energy of the molecules due to which the molecules start vibrating randomly. These random motions result in the breakage of bonds. Thus secondary and tertiary structures cannot remain intact.