Question

multiple choice question
the main function of the rough er is ____ synthesis while the main function of the smooth er is ____ synthesis.

○ lipid; dna
○ protein; lipid
○ protein; atp
○ lipid; protein
○ protein; dna

Explanation:

To solve this, we recall the functions of rough and smooth endoplasmic reticulum (ER). The rough ER has ribosomes on its surface, which are involved in protein synthesis. The smooth ER lacks ribosomes and is mainly responsible for lipid synthesis (and also detoxification, carbohydrate metabolism, etc.). Now let's analyze the options:

• Option "lipid; DNA": Rough ER doesn't synthesize lipids, and DNA synthesis is not a function of smooth ER. Eliminate.
• Option "protein; lipid": Rough ER (with ribosomes) synthesizes proteins, smooth ER synthesizes lipids. This matches.
• Option "protein; ATP": ATP synthesis is mainly by mitochondria, not smooth ER. Eliminate.
• Option "lipid; protein": Reverse of the correct functions. Eliminate.
• Option "protein; DNA": DNA synthesis is not a function of smooth ER. Eliminate.

Answer:

B. protein; lipid (assuming the option with "protein; lipid" is labeled as such, here the second option in the list: "protein; lipid")