Which statement about Smooth endoplasmic reticulum is true?

• A. Contains Many Ribosomes for Protein Synthesis
• B. Site of Protein Modification, Glycogen, Lipid Synthesis, and Chemical Redox
• C. Produces Mitochondrial DNA
• D. Primary Site of Photosynthesis

Answer: (B)

Smooth endoplasmic reticulum lacks ribosomes, so it isn’t the main site of protein synthesis. Its roles center on lipid synthesis, carbohydrate metabolism (in some cells like liver cells it supports glycogen-related processes via enzymes such as glucose-6-phosphatase), and detoxification that involves redox chemistry (for example, cytochrome P450 enzymes perform oxidation reactions to make compounds more water-soluble). These functions align with the statement that describes lipid synthesis, glycogen-related carbohydrate metabolism, and chemical redox. The other options point to functions of other organelles (ribosome-rich rough ER for protein synthesis, mitochondrial DNA handling in mitochondria, and chloroplasts for photosynthesis), so they don’t fit the smooth ER as well.