Lactic Acid Guide
Why Is Lactic Acid Produced?
To understand why lactic acid is produced we need to first understand the process by which cells produce energy. Cells can use several different substrates (fats, sugars, proteins) to make energy but for the purposes talked about here, sugars such as glucose or glycogen are the most important. This is done via a process called glycolysis.
Glycolysis is one of the most fundamental pathways in cellular metabolism. It is a process by which a substrate, glucose, is converted into pyruvate, and it yields the high-energy molecule ATP, which is the universal currency of energy in the body.
Glycolysis actually occurs outside of mitochondria, which are the main furnaces of many cells, and does not require oxygen to occur. This is important as everything needed to carry out glycolysis is waiting in the cells and the reaction can be initiated at a moments notice, thus providing instant energy to the cells.
The reaction in glycolysis goes as follows
Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O
As you can no doubt see, one molecule of glucose produces 2 molecules of pyruvate and 2 x ATP (energy molecules). The important molecule here when it comes to lactate is the pyruvate.
But it doesn’t end here……
Pyruvate is by no means the end product of the production of ATP from glucose. In well-oxygenated muscle cells in low demand conditions, the pyruvate then enters the mitochondria and is converted to carbon dioxide in a sustainable reaction (as long as there is a continuous supply of oxygen to meet demand).
If however there is not enough oxygen to meet demand, or if the energy requirements of the cell exceed production via oxidative phosphorylation, then the pyruvate can be converted to lactate, thus removing the build up of pyruvate and allowing glycolysis to continue occurring.