This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Major site of protein glycosylation is 
Select and explain. 
A. ER and golgi body, B. Ribosome and golgi body, C. ER and ribosome, D. Ribosome and cytoplasm
A: ER and golgi body
Answer: A: ER and golgi body 
Explanation: Because many glycosylation reactions occur within the lumen of the Golgi apparatus, carrier systems (permeases and transpoers) are required to transpo nucleotide sugars across the Golgi membrane.Ref: Harpers Illustrated Biochemistry, 30th edition, page no: 572