Being able to draw fructose is an important step to understanding important chemical reactions inside of living cells such as Glycolysis or Gluconeogenesis. Fructose is also an important source of energy for cells in many different organisms that range from bacteria to mammals. Being able to easily draw fructose is a fundamental step to learning higher level chemistry or biology.
Fructose is an isomer of glucose because they share the same empirical formula. The empirical formula of fructose is C6H12O6. The empirical formula tell you that every time you draw fructose there should be:
- 6 Carbon atoms
- 6 Oxygen atoms
- 12 hydrogen atoms.
Since carbon is the backbone of organic molecules I suggest counting Carbon atoms first, then oxygen, and placing hydrogen in any free locations. If you know how many Carbon and Oxygen atoms are in glucose then remembering where the 12 hydrogen atoms go is like filling in the free space.
The Open Chain Structure
An easy way to draw the open chain structure of fructose is to follow these 3 steps:
You should only need to remember which side of the chain the oxygen atoms are. If you count the number of bonds on each carbon, and count the number of bonds of each oxygen atom, you can fill in the rest of the structure with hydrogen atoms.
The Cyclic (ring) Structure
When drawing the ring structure of fructose, most of the 4 of the 6 carbons atoms are represented by a bent line. The other two carbons are in positions that allow fructose to attach chemical groups such as phosphate during glycolysis. Just for technical purposes I am showing the alpha-D-fructose molecule below. This is the form of glucose that should be studied in most biology courses.
[gn_note color=”#21ab2f”]The OH groups always bonds to the ring from the oxygen atom. -OH and HO- are correct but -HO is not. Remember the bonding rules above[/gn_note].