Question

Which of the following is/are examples of denaturation of protein?

• A. Coagulation of egg white
• B. Curdling of milk
• C. Clotting of blood
• D. Both (1) and (2)

Hint:

Denaturation of proteins can be caused by heat, acid, or mechanical agitation. This leads to a loss of their functional structure.

Answer 1

The Correct Option is D

To solve the problem, we need to identify which of the given options are examples of protein denaturation.

1. Understanding Protein Denaturation:
Protein denaturation occurs when a protein loses its native three-dimensional structure (secondary, tertiary, or quaternary) due to the disruption of non-covalent interactions (e.g., hydrogen bonds, hydrophobic interactions) or covalent bonds (e.g., disulfide bridges), without breaking the primary peptide bonds. Common causes include heat, pH changes, chemicals, or mechanical stress.

2. Evaluating Option A (Coagulation of egg white):
Coagulation of egg white occurs when it is heated, as during cooking. The heat disrupts the hydrogen bonds and hydrophobic interactions in the egg white proteins (e.g., albumin), causing them to unfold and aggregate, turning the liquid egg white into a solid. This is a classic example of protein denaturation.

3. Evaluating Option B (Curdling of milk):
Curdling of milk happens when an acid (e.g., lemon juice or vinegar) is added, lowering the pH. This alters the charge on the milk proteins (e.g., casein), disrupting ionic and hydrogen bonds, causing the proteins to unfold and aggregate into curds. This process is also an example of protein denaturation.

4. Evaluating Option C (Clotting of blood):
Blood clotting is a physiological process involving the conversion of fibrinogen (a soluble protein) into fibrin (an insoluble protein) by the enzyme thrombin, forming a mesh that traps blood cells. This is a controlled, enzymatic process that does not involve the unfolding or loss of protein structure due to external factors like heat or pH. Instead, it is a functional change in protein structure, not denaturation.

5. Evaluating Option D (Both 1 and 2):
Option D refers to both A (coagulation of egg white) and B (curdling of milk). Since both A and B are examples of protein denaturation, while C is not, option D correctly identifies the examples of denaturation.

Final Answer:
The examples of protein denaturation are A (coagulation of egg white) and B (curdling of milk), so the correct option is D (Both 1 and 2).