Glycolysis, the first series of steps in Aerobic Cellular Respiration for extracting energy from sugars. Glycolysis is considered the most ancient and fundamental metabolic pathway for the following reasons:
It is nearly universal, being found in almost all types of organisms
Occurs in the cytosol, without the help of any complex organelles
Does not require oxygen, which only became abundant 2.5 billion years ago (1.5 billion years after life began)
When the word is broken down, we see exactly what occurs during Glycolysis- Glyco: Sugar + Lysis: Splitting
Glycolysis consists of 10 individual enzyme catalyzed reactions (found on p.171). Overall, it is the cleaving of a glucose (a 6 Carbon ring) molecules into 3 carbon chains called Pyruvate, as well as the production of 2 ATP molecules and an 2 NADH modules.
These two ATP molecules contain ~62kJ, approximately 2.2% of the 2870kJ of energy found in glucose. While some of the energy is lost as heat (2nd Law of Thermodynamics), the majority of that energy is still contained in the Pyruvates and NADH molecules.
Glycolysis is divided into two sections (5 reactions each)- the Investment phase and the Payoff phase. To begin glycolysis, an investment of 2 ATP is required to begin the splitting on sugar. The end of the Payoff phase produces 4 ATP (net result - +2 ATP).
Read p.172-174. Questions p.182#1-2