Review Question - QID 100086

The smooth endoplasmic reticulum (ER) is involved in steroid synthesis, chemical detoxification, lipid metabolism and gluconeogenesis.

High concentrations of smooth ER are found in hepatocytes, kidney, adrenal cortex, and corpus luteum. In muscle a modified smooth ER called the sarcoplasmic reticulum releases calcium for muscle contraction.

Kirk et al. review ACTH stimulation of cells with prominent smooth ER in the adrenal cortex results in secretion of the cholesterol-derived steroid hormones: mineralocorticoids, glucocorticoids, and androgens. Overstimulation of adrenal cells due to increased ACTH production is one cause of Cushing's syndrome. Other causes, symptoms, and treatments for Cushing's syndrome are reviewed in this article.

Takamura et al. present a case study of a 60-year old woman with Cushing syndrome due to a functioning adrenal mass. On microscopy, cells in the mass were found to have well-developed smooth ER, corresponding to their role in steroidogenesis.

Illustration A is a diagram showing the relative locations of smooth and rough ER in the cell.
Illustration B compares appearance of smooth ER to rough ER on electron microscopy.

Incorrect Answers:
Answer 1: The main function of the rough ER is the ribosome-mediated synthesis of proteins.
Answer 2: The golgi apparatus is a site for the trafficking of proteins and lipids.
Answer 3: Peroxisomes contain several enzymes necessary for oxidative processes.
Answer 5: The nucleolus plays a role in the formation of ribosomes.