[Ah Beng]

Dexoyribose (C5 H10 04) and Ribose (C5 H10 O5) are the 'pentose sugars' present in DNA and RNA respectively. By definition, sugars are a subset of carbohydrates. By definition, carbohydrates (= hydrated carbons) always have their ratio of hydrogen to oxygen as 2:1, as in water.

So are Deoxyribose and Ribose, not carbohydrates?

[Yggdrasil]

I would classify ribose and deoxyribose as carbohydrates.  Biology is a very inexact science.  Although classifying all compounds with the formula C_n(H₂O)_n as carbohydrates is a good general rule there are many exceptions.  Derivatives of compounds which follow this rule that are classified as carbohydrates. For example, N-acetylglucosamine (C₈H₁₆O₆N₂) is an important monosaccharide and it is considered a carbohydrate because it is a derivative of glucose.

[Ah Beng]

Thanks very much, Yggdrasil!