1. Cells have the ability to extract stored energy from sugar molecules. Energy release begins with the common sugar called glucose. Cells use a process called glycolysis breaks glucose down to pyruvate with release of energy ("glycolysis" refers to taking apart sugars). Glycolysis produces energy in the form of ATP and NADH.
2. The product of glycolysis is a three carbon sugar, pyruvate. Further breakdown occurs in a process called the Krebs cycle. The ultimate result of the Krebs cycle is to breakdown the sugar to CO2 with release of ATP and much more NADH.
3. NADH is a molecule that carries electrons. These electrons can be used to generate many more molecules of ATP. Electrons released in the Krebs cycle are transfered to proteins called coenzymes. As they pass from one coenzyme to another they are used to generate ATP molecules.

Pages in this unit:

1. There are three types of energy releasing pathways.
2. Glycolysis
3. Aerobic respiration and electron transport phosphorylation
4. Anaerobic respiration