Q.49 Proteins destined to be secreted, move through the secretory pathway in which of the following order
A. Cell surface
B. Rough endoplasmic reticulum
C. Secretary vesicle
D. Transport vesicle
E. Golgi complex
Choose the correct answer from the options given below:
1. A, B, C, D, E
2. A, B, D, C, E
3. E, B, C, D, A
4. B, D, E, C, A
Protein Secretory Pathway Order
Proteins destined for secretion follow a specific pathway through cellular compartments. The correct order is Rough ER → Transport Vesicle → Golgi Complex → Secretory Vesicle → Cell Surface.
Correct Answer
The right choice is 4. B, D, E, C, A (Rough Endoplasmic Reticulum → Transport Vesicle → Golgi Complex → Secretory Vesicle → Cell Surface).
This sequence reflects the classical secretory pathway where proteins are synthesized, processed, sorted, and released.
Pathway Overview
Proteins with signal peptides enter the Rough ER for folding and initial modifications like glycosylation. They move via transport vesicles to the Golgi for further processing, then exit in secretory vesicles to fuse with the plasma membrane.
Option Analysis
| Option | Sequence | Correct/Incorrect | Explanation |
|---|---|---|---|
| 1. A, B, C, D, E | Cell surface → RER → Secretory vesicle → Transport vesicle → Golgi | Incorrect | Starts at cell surface, reversing the flow; proteins don’t begin secretion there. |
| 2. A, B, D, C, E | Cell surface → RER → Transport vesicle → Secretory vesicle → Golgi | Incorrect | Begins incorrectly at cell surface and places Golgi last, missing maturation steps. |
| 3. E, B, C, D, A | Golgi → RER → Secretory vesicle → Transport vesicle → Cell surface | Incorrect | Places Golgi before RER, opposite of synthesis direction. |
| 4. B, D, E, C, A | RER → Transport vesicle → Golgi → Secretory vesicle → Cell surface | Correct | Matches ER entry, vesicular transport to Golgi, sorting into secretory vesicles, exocytosis. |
Why This Matters for Exams
This pathway is key for NEET, CSIR NET, and biotech exams testing cell biology. Recall: RER handles translation, Golgi modifies, vesicles deliver.
