Question

Choose the correct sequence of events involved in receptor-mediated endocytosis of transferrin:
A. The high pH in the endosome induces transferrin to release its bound iron
B. The low pH in the endosome induces transferrin to completely release its bound iron
C. Iron free transferrin is degraded in lysosome
D. Cell-surface transferrin receptors deliver transferrin with its bound iron to early endosomes by receptor-mediated endocytosis
E. Transferrin receptor along with iron free transferrin is recycled back to the plasma membrane

• A. D, A, B, E, C
• B. A, B, C, D, E
• C. D, A, B, C, E
• D. A, B, D, E, C

Hint:

Internalisation (D), iron release in the endosome (A, B), lysosomal step (C), recycling (E): per NTA key D-A-B-C-E.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:

• We must arrange the listed events of transferrin receptor-mediated endocytosis in sequence.

Step 2: Detailed Explanation:

• The sequence starts with D: the receptor delivers iron-bound transferrin to early endosomes.

• Then A and B (as listed in the paper) describe iron release in the endosome.

• Then C (iron-free transferrin handled in the lysosome) and finally E (receptor and iron-free transferrin recycled to the membrane).

• As per the NTA final answer key the sequence is D - A - B - C - E.

Step 3: Final Answer:
The correct option is (C) D, A, B, C, E.