Question

When the molecular weight of human immunoglobulin light chain is 24 kDa, the total molecular weight of human IgG is ______ kDa.

Hint:

IgG = 2 heavy chains (≈50 kDa each) + 2 light chains (≈25 kDa each) → total ≈150 kDa.

Answer 1

Correct Answer: 140

Step 1: Recall the structure of IgG.
An IgG molecule consists of:
- 2 heavy (H) chains, and
- 2 light (L) chains.
Step 2: Given data.
Molecular weight of light chain (L) = 24 kDa.
Molecular weight of heavy chain (H) = approximately 50 kDa (known biological constant).
Step 3: Calculate total molecular weight.
\[ \text{Total MW} = (2 \times \text{H}) + (2 \times \text{L}) = (2 \times 50) + (2 \times 24) = 100 + 48 = 148~\text{kDa} \] Rounded off to the nearest significant figure → 150 kDa.
Step 4: Conclusion.
Therefore, the molecular weight of human IgG is approximately 150 kDa.