Smooth endoplasmic reticulum synthesizes
A) Carbohydrates
B) Proteins
C) Steroids and lipids
D) All of the above

Hint: Smooth endoplasmic reticulum (Smooth ER) is a membrane organelle present in most eukaryotic cells. It is a branch of the endoplasmic reticulum endomembrane system.

Complete Answer:
>The smooth ER is characterised by the absence of membrane-bound ribosomes from the other areas of the endoplasmic reticulum. This organelle is often morphologically distinct, often made up of tubular structures called cisternae.
>The cells that secrete these materials, such as testicular cells, ovaries, and skin oil glands, have an abundance of smooth endoplasmic reticulum.
>Its key functions are the synthesis of lipids, steroid hormones, the detoxification of toxic metabolic by-products and the storage and metabolism of calcium ions within the cell.
>The smooth endoplasmic reticulum also applies to the metabolism of carbohydrates and steroids.
>Smooth ER is prevalent in liver cells that handle harmful chemicals, in endocrine system cells such as those that manufacture steroid hormones, and in excitable cells such as neurons and muscle cells that use $Ca_2$ + signalling.
>The smooth endoplasmic reticulum (SER) is distinguished from the rough endoplasmic reticulum ( RER), the other basic form of endoplasmic reticulum, by the lack of ribosomes, which are protein-synthesizing particles which are found attached to the outer surface of the RER to give the membrane its "rough" appearance. SER occurs in both animal and plant cells.
>The function of the SER can differ depending on the type of cell. In certain cells, such as the adrenal gland and some other endocrine glands.
>In the liver, SER enzymes catalyse reactions that make medicines, metabolic waste and toxic chemicals water-soluble, thus leading to their detoxification or elimination from the body.

Hence the correct answer is option (C) Steroids and Lipids.

Note:The smooth endoplasmic reticulum network enables an expanded surface area to be dedicated to the storage of key enzymes.