<P> Simplified Theoretical Reaction: C H O → (\ displaystyle \ to) 2C H O + 2 ATP (120 kJ) Lactic Acid Fermentation is commonly known as the process by which mammalian muscle cells produce energy in anaerobic environments, as in instances of great physical exertion, and is the simplest type of fermentation . It starts along the same pathway as aerobic respiration, but once glucose is converted to pyruvate proceeds down one of two pathways and produces only two molecules of ATP from each molecule of glucose . In the homolactic pathway, it produces lactic acid as waste . In the heterolactic pathway, it produces lactic acid as well as ethanol and carbon dioxide . Lactic acid fermentation is relatively inefficient . The waste products lactic acid and ethanol have not been fully oxidized and still contain energy, but it requires the addition of oxygen to extract this energy . </P> <P> Generally, lactic acid fermentation occurs only when aerobic cells are lacking oxygen . However, some aerobic mammalian cells will preferentially use lactic acid fermentation over aerobic respiration . This phenomenon is called the Warburg effect and is found primarily in cancer cells . Muscles cells under great exertion will also use lactic acid fermentation to supplement aerobic respiration . Lactic acid fermentation is somewhat faster, although less efficient, than aerobic respiration, so in activities like sprinting it can help quickly provide needed energy to muscles . </P> <P> Cellular respiration takes place in the cristae of the mitochondria within cells . Depending on the pathways followed, the products are dealt with in different ways . </P> <P> CO is excreted from the cell via diffusion into the blood stream, where it is transported in three ways: </P>

Where is most of the carbon dioxide given off in cellular respiration made