Question

The smooth endoplasmic reticulum is a major site for the synthesis of
(a)Proteins
(b)Lipids
(c)Carbohydrates
(d)Vitamins

Answer 1

Hint: Smooth Endoplasmic Reticulum secretes Cholesterol which are steroid precursors, cells in organs with the higher secretion of cholesterol derivatives like testes, ovaries, sebaceous glands have been seen with excess SER in them.

Complete answer:
Smooth Endoplasmic Reticulum (SER) is a fine membranous meshwork of tubular vesicles in the cytoplasm of a Eukaryotic cell. The main function of SER is the synthesis and storage of Lipids, Phospholipids, and cholesterol which take part in the production of the cell membrane as well as membranes of various other cell organelles

Additional Information: The function of SER varies with variation in the cell type and the organ of which it is a part.
-In Endocrine glands, it forms the Steroid hormones which are derivatives of Cholesterol.
-In the liver, the SER secretes certain enzymes that convert insoluble metabolites, drugs, and harmful chemicals into soluble compounds helping in the removal of substances from the body. Another role of SER is to catalyze the conversion of glycogen to glucose in the liver.
- In the cells of Skeletal muscles SER is a specialized membrane structure called the sarcoplasmic reticulum Which is a storage site for calcium ions that are taken up from the cytoplasm of the cells. When the muscle cell is triggered by nerve stimuli, the calcium ions are secreted into the cell thus resulting in muscle contraction. Thus the sarcoplasmic reticulum acts in maintaining the calcium ion concentrations in the cytoplasm of skeletal muscle cells in order to undergo proper excitation-contraction of the muscles. The calcium ion channels are the main components of skeletal muscle functioning.
So, the correct answer is 'Lipids'

Note: The Rough Endoplasmic Reticulum is also another continuous membrane organelle in the cytoplasm of the cell. It differs from the SER due to the presence of small round organelles called the ribosomes attached to their surface. The function of the ribosomes is the production of protein.