Question

Smooth endoplasmic reticulum ____________.

• A. is a site for the synthesis of carbohydrates
• B. has ribosomes attached to its surface
• C. is the major site for the synthesis of lipids
• D. is actively involved in protein synthesis

Hint:

Remember this clear division of labor for the Endoplasmic Reticulum: \[ \text{\textbf{R}ough ER (\textbf{R}ibosomes Present)} \quad \Longrightarrow \quad \text{\textbf{P}rotein Synthesis} \] \[ \text{\textbf{S}mooth ER (\textbf{S}no Ribosomes)} \quad \Longrightarrow \quad \text{\textbf{L}ipid \& Steroid Hormone Synthesis} \]

Answer 1

The Correct Option is C

Step 1: Recall the two kinds of ER.
The endoplasmic reticulum exists as rough ER and smooth ER, differing by ribosomes.
Step 2: Describe rough ER.
Rough ER has ribosomes on its surface and handles protein synthesis and folding.
Step 3: Describe smooth ER.
Smooth ER lacks surface ribosomes, giving it a smooth tubular look.
Step 4: State the main SER function.
The smooth ER is the major site for synthesis of lipids such as phospholipids, fatty acids, and steroids. So this is the answer.
Step 5: Reject the protein and ribosome options.
Having attached ribosomes and doing protein synthesis are features of rough ER, not smooth ER.
Step 6: Reject carbohydrate synthesis and conclude.
Complex carbohydrate processing mainly happens in the Golgi, not the SER. Therefore the smooth ER is the major site for lipid synthesis.
\[ \boxed{\text{is the major site for the synthesis of lipids}} \]