MCAT® ExamBiological and Biochemical Foundations of Living SystemsEasy
A patient is diagnosed with a rare genetic disorder characterized by the inability to properly synthesize certain steroid hormones. Further investigation reveals a defect in the smooth endoplasmic reticulum (SER) of their adrenal cortical cells. Which of the following functions of the SER is most likely impaired in this patient?
- AProtein synthesis and modification
- BLipid and steroid hormone synthesis
- CStorage and release of calcium ions
- DDetoxification of drugs and poisons
Show answer & explanationAnswer & explanation
Correct answer: B. Lipid and steroid hormone synthesis
The smooth endoplasmic reticulum is primarily responsible for the synthesis of lipids, including steroid hormones, and also for detoxification and calcium storage. A defect in steroid hormone synthesis directly points to an impairment in the SER's lipid synthesis function.
Why the other options are wrong
- A. Protein synthesis and modification primarily occur in the rough endoplasmic reticulum and ribosomes.
- C. The SER does store and release calcium ions, but this function is not directly linked to the synthesis of steroid hormones mentioned in the patient's symptoms.
- D. While the SER is involved in detoxification, the primary symptom described is related to steroid hormone synthesis, not detoxification.
Smooth Endoplasmic Reticulum (SER)
A network of membranes involved in various metabolic processes, including lipid synthesis, detoxification, and calcium storage, but lacking ribosomes.
- Lacks ribosomes, hence 'smooth'.
- Synthesizes lipids, phospholipids, and steroids.
- Metabolizes carbohydrates.
- Detoxifies drugs and poisons.
- Stores calcium ions.
Memory trick: Smooth SER: Steroids, Storage, Synthesis, and S-Detox (Smooth Detox)