EVERYDAY SCIENCE

Detailed explanation-1: -Smooth endoplasmic reticulum (sER) is (a part of) endoplasmic reticulum that is tubular in form and lacks ribosomes. It is present in eukaryotic cells and is associated with lipid synthesis, carbohydrate metabolism, regulation of calcium concentration, and drug detoxification.

Detailed explanation-2: -The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells. The main function of the SR is to store calcium ions (Ca2+).

Detailed explanation-3: -The endoplasmic reticulum (ER) plays a central role in calcium signaling as a source of calcium that is released into the cytosol upon cell activation [2].

Detailed explanation-4: -The SER is a storage site for calcium within cells. Calcium is pumped into the SER by active transport and released in response to hormonal signals. This is particularly important in muscle cells where the SER is so prominent it has a special name, the sarcoplasmic reticulum.

Detailed explanation-5: -The recent demonstration that the IP3 receptor, which has similarities with the calcium release channel in the SR is also localised in the ER membrane suggests that calcium stored in the ER is important for intracellular signalling.