Which of the sequences of events correctly describes the progress of a protein that will be secreted from the cell?1. SRP binds to the growing polypeptide chain and to the ribosome. 2. Translation resumes. 3. SRP binds to its receptor. 4. The signal sequence is cleaved. 5. Protein synthesis begins in the cytosol. 6. Translation pauses. a) 5 → 1 → 6 → 3 → 2 → 4
b) 5 → 6 → 1 → 3 → 2 → 4
c) 3 → 6 → 1 → 2 → 4 → 5

A) 5 → 1 → 6 → 3 → 2 → 4

Explanation:

The protein synthesis takes place in the ribosome which is either attached to the endoplasmic reticulum or they float freely in the cytosol.

The proteins are targeted to different components of the cells depending on the signal molecules they bind.

The proteins which are transported to the ER forms signal sequences composed of hydrophobic amino acid. This signal sequence then is recognised by the Signal recognition particle which directs the protein to ER. The binding of SRP to sequence slows down the process of translation.

The SRP then binds to its receptor present on the ER which allows the translation to again resume. The growing protein then enters the lumen of the ER and then the signal sequence cleaves.

Thus, Option-A is the correct answer.

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