Afeature that distinguishes ribose from deoxyribose is the absence of an oh at the:

The difference between ribose and deoxyribose is that in ribose the second carbon atom carries hydroxyl group while in deoxyribose, the second carbon atom contains only hydrogen atom. Ribose and Deoxyribose make up the backbone of RNA and DNA respectively. 

Pro insulin undergoes extensive posttranslational modification along the production pathway .