One of the additional functions of Smooth Endoplasmic Reticulum (SER) is

The Endoplasmic Reticulum (ER) is a vital eukaryotic organelle divided into rough and smooth types based on the presence of ribosomes. While the Rough ER is primarily responsible for protein synthesis, the Smooth Endoplasmic Reticulum (SER) lacks ribosomes and performs several specialized metabolic functions. These include the synthesis of lipids, phospholipids, and steroid hormones. Crucially, the SER plays a major role in the detoxification of drugs, poisons, and toxic substances, particularly within liver cells where it contains specific enzymes to facilitate this process. Additionally, the SER is involved in carbohydrate metabolism and the storage of calcium ions, which are essential for muscle contraction. While lipid synthesis is a primary function, detoxification is frequently highlighted as a critical 'additional' or specialized function in biological contexts, making option 4 the most comprehensive answer for specialized SER roles.

Sources

1. [1] https://www.sciencedirect.com/topics/immunology-and-microbiology/smooth-endoplasmic-reticulum