This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous System, Subject name: Physiology
Steroid synthesis occurs in which organelle? 
Select and explain. 
A. Lysosome, B. Smooth endoplasmic reticulum, C. Rough endoplasmic reticulum, D. Lysozyme
B: Smooth endoplasmic reticulum
Answer: B: Smooth endoplasmic reticulum 
Explanation: Ans. B Smooth endoplasmic reticulum* The smooth endoplasmic reticulum is continuous with the rough endoplasmic reticulum and does not contain any ribosomes. Although it has several functions, the sER is specialized for the production of steroid hormones in cells of the adrenal cortex.* Remember that cholesterol is the main precursor for steroid hormones produced in the adrenal cortex and the gonads.