Smooth endoplasmic reticulum (SER) is a network of tubules and vesicles within a cell that lacks ribosomes on its surface. Its main functions include lipid synthesis, detoxification, and calcium storage.

Option 1: Transport of materials is a function carried out by the smooth endoplasmic reticulum. SER helps in the transport of lipids and proteins between different parts of the cell.

Option 2: The synthesis of lipids is a primary function of the smooth endoplasmic reticulum. SER is involved in the production of various lipids, including phospholipids and cholesterol.

Option 3: The synthesis of proteins is NOT carried out by the smooth endoplasmic reticulum. Protein synthesis primarily occurs in the rough endoplasmic reticulum (RER), which has ribosomes attached to its surface.

Option 4: The synthesis of steroid hormones is also a function of the smooth endoplasmic reticulum. SER is responsible for the synthesis of important steroid hormones, including estrogen and testosterone.

In conclusion, the correct answer is option 3 - Synthesis of protein. The synthesis of proteins is primarily carried out by the rough endoplasmic reticulum, not the