deoxyribose

Ribose is a five carbon monosaccharide (similar to that of glucose) that is most known in its de-oxygenated state 'deoxyribose' as a component of DNA. In the case of deoxyribose, a hydroxyl group has been replaced with a single hydrogen atom. Deoxyribose has the chemical formula C₅H₁₀O₄.

  H H H
  | |/
  O-C5  O     OH
    | /   \  /
  H-C4     1C-H
     \ 3 2 /
    H-C - C-H
      |   |
     HO   H

The bold hydrogen atom above (lower right corner) is what makes this deoxyribose. In ribose, that is another hydroxyl group (OH). Traditionally, the carbon atoms are numbered starting in the upper right as 1 and then progressing clockwise around. The formal name of this sugar is 2-deoxy-D-ribose indicating that the de-oxygenated segment occurs on the second carbon atom. The strands of DNA use this numbering to indicate the orientation - there is the 3 end and the 5 end.

This sugar makes up the backbone of DNA along with phosphate groups. Below is a diagram which shows the bonds within DNA. The top oxygen atom bonds to carbon atom number 3.

     |
     O
(-)  |
 O - P = O
     |
     O H H
      \|/
       C   O     (nucleic acid)
       | /   \  /
     H-C       C-H
        \     /
       H-C - C-H
         |   |
         O   H
         |