Cellular respiration is the process of oxidizing food molecules such as glucose to carbon dioxide and water (Kimball).
Energy is released in the form of ATP, which is used for all the energy consuming processes of the cell.
Glycolysis, the Krebs Cycle, and Electron Transport Phosphorylation
There are two stages to the process: glycolysis, which is the breakdown of glucose from the diet to pyruvic acid and the complete oxidation of pyruvic acid to carbon dioxide and water. In eukaryotes, glycolysis takes place in the cytosol and the remaining processes take place in the mitochondria. The outer membrane of mitochondria contains complexes of integral membrane proteins which form channels through which a variety of molecules enter and leave. The inner membrane contains five complexes of integral membrane proteins: NADH dehydrogenase, succinate dehydrogenase, cytochrome c reductase, cytochrome c oxidase, and ATP synthase. The matrix contains a mixture of soluble enzymes that catalyze the respiration of pyruvic acid and other small organic molecules.
In glycolysis, there are two separate phases: the first is the chemical priming phase requiring energy in the form of ATP, and the second is the energy-yielding phase (Devlin; King). In the first phase, 2 equivalents of ATP are used to convert glucose to fructose 1,6-bisphosphate. In the second phase, the fructose 1,6- bisphosphate is degraded to pyruvate with the production of 4 equivalents of ATP and 2 equivalents of NADH. The ATP-dependent phosphorylation of glucose to form glucose 6-phosphate is the first reaction of glycolysis and is catalyzed by tissue-specific isoenzymes called hexokinases. The second reaction is an isomerization in which glucose 6-phosphate is converted to fructose 6-phosphate by phosphohexose isomerase. Next, a second ATP molecule converts fructose 6-phosphate to fructose 1,6-bisphosphate using the enzyme 6-phosphofructo-1-kinase. In the secon...