This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Translation, Subject name: Biochemistry
Ribosomes are attached to - 
Select and explain. 
A. Nucleus, B. RER, C. Smooth ER, D. Mitochondria
B: RER
Answer: B: RER 
Explanation: Ans. is 'b' i.e., RER Ribosomeso Ribosomes are the actual sites of protein synthesis. The ribosomes are small granules of RNAs. Ribosomes are usually occur in clusters called polyribosomes attached to one mRNA molecule, an arrangement that increases the rate of polypeptide synthesis. There are two types of polyribosomes : -Free (cytosolic) : - Present free in cytosol.Bound polyribosome : - Present on rough ER.