Question

Which of the following is correct about the endoplasmic reticulum?

• A. The smooth endoplasmic reticulum is involved in glycosylating the proteins
• B. The rough endoplasmic reticulum is involved in synthesis of proteins that will either be inserted into cellular membranes or be secreted from the cell
• C. The lumen of rough endoplasmic reticulum is highly reducing in nature
• D. The smooth endoplasmic reticulum synthesizes globular proteins and rough endoplasmic reticulum synthesizes fibrillar proteins

Hint:

• RER → Protein synthesis (secretory/membrane proteins)
• SER → Lipid synthesis, detox
• ER lumen → Oxidizing environment

Answer 1

The Correct Option is B

Concept: The endoplasmic reticulum (ER) has two types:
• Rough ER (RER): Studded with ribosomes, involved in protein synthesis.
• Smooth ER (SER): Lacks ribosomes, involved in lipid synthesis and detoxification.

Step 1: Analyzing each statement.

• (A): Incorrect — Glycosylation mainly occurs in ER lumen and Golgi, not specifically by SER.
• (B): Correct — RER synthesizes proteins destined for secretion or membrane insertion.
• (C): Incorrect — ER lumen is oxidizing, not reducing (important for disulfide bonds).
• (D): Incorrect — SER does not synthesize proteins; ribosomes (RER) do.

Step 2: Selecting the correct answer.
Only statement (B) is correct.