<prompt> The cellular component of protein synthesis is :Smooth endoplasmic reticulumRough endoplasmic reticulumRibosomesMitochondria  <response>: Ribosomes Rough endoplasmic reticulum Rough ER is that ER on which ribosomes are attached and protein synthesis occurs in ribosomes. So, best answer here is 3. Fig.: Free ribosomes present in cytoplasm not attached to ER Fig.: Ribosomes attached to cytosolic side of ER BUT SER is responsible for the synthesis of lipids, in detoxification and Ca sequestration release. 