2018 · Q23
A protein is synthesized in the endoplasmic reticulum bound ribosomes and it targets to the inner thylakoid space of chloroplast. How many double-layered membrane layers it has to pass to reach its destination?
General KnowledgeBiology
- A2
- B3
- C4
- D5
Explanation
The protein begins at the ER-bound ribosomes, entering the secretory pathway across the ER membrane. To reach the thylakoid lumen it must then cross the chloroplast's outer envelope membrane, its inner envelope membrane and finally the thylakoid membrane itself. That is four membrane crossings in total. Hence the answer is 4.