Sugars are carbohydrates - organic molecules with the empirical formula Cx
- that are used as energy sources and structural components by all life on earth. Simple sugars contain one sugar unit, or saccharide. Other carbohydrates may contain 2 to several tens of thousands of saccharides.
Sugars in Nucleic Acids
The backbone of nucleic acids contains alternating sugar and phosphate units. RNA contains the sugar ribose, while DNA contains the sugar 2'-deoxyribose. The latter differs in the absence of an -OH group at the 2' position of the ring.
Simple sugars can be represented as a straight chain a form 5-or 6-membered ring. These two forms are equivalent and interchangeable, but in solution the ring form predominates. Additionally, there are several projections - or ways of drawing a sugar. The linear form is typically shown as a Fischer projection
, while the ring form is shown as a Haworth projection