AKA blood sugar, and corn sugar.
Glucose is our body's primary source of energy. When we digest carbohydrates, our stomach breaks them down into glucose, which is carried throughout the body by our blood stream. Insulin binds with the glucose, making it available for our cells to use; what is not used immediately is stored in the liver as glycogen. (If your body cannot regulate your blood sugar levels correctly, this may result in diabetes.)
Every carbohydrate is originally formed through photosynthesis. The most common model of photosynthesis is:
6 (CO2) + 12 (H2O) + light energy = 1 (C6H12O6) + 6 (O2) + 6 (H2O)
The glucose (C6H12O6) then stores the energy (Chemical energy at this point) in the plant until it is needed. It may be stored as a simple sugar or as a starch, or even used as a structural component of the plant, such as cellulose. It is then broken down, releasing the energy. Humans use glucose and other forms of sugar coming from plants to provide all of their energy. As only plants (and some protists) make glucose, they are the base of all food chains.
Glucose is also used as a component in the synthesis of some amino acids and fatty acids.
See ATP.
Some isomers of glucose include dextrose, galactose, fructose, and mannose.