A Level Biology Practice Exam

What is the primary function of the smooth endoplasmic reticulum?

1. Protein synthesis

2. Lipid and carbohydrate synthesis

3. DNA replication

4. Ribosome production

The correct answer is: Lipid and carbohydrate synthesis

The primary function of the smooth endoplasmic reticulum (SER) is indeed lipid and carbohydrate synthesis. The smooth endoplasmic reticulum lacks ribosomes on its surface, distinguishing it from the rough endoplasmic reticulum which is directly involved in protein synthesis. Instead, the smooth ER plays a crucial role in the metabolism of lipids, including the synthesis of cholesterol, phospholipids, and steroid hormones. Additionally, it is involved in carbohydrate metabolism, such as the conversion of glucose-6-phosphate to glucose, which is important for energy production and storage. The smooth ER also functions in detoxification processes, such as the breakdown of drugs and poisons in liver cells, further highlighting its importance in maintaining cellular health and function. This diverse role in lipid and carbohydrate synthesis makes the smooth endoplasmic reticulum essential for various physiological processes in cells.