glucose
In food chemistry, the substances known as antioxidants are reducing agents. Ascorbic acid vitamin C; C6H8O6 is thought to retard potentially damaging oxidation of living cells. In the process, it is oxidized to dehydroascorbic acid C6H6O6 . In the stomach, ascorbic acid reduces the nitrite ion NO2 to nitric oxide NO : C6H8O6 + 2H+ + 2NO2 C6H6O6 + 2H2O + 2NO If this reaction did not occur, nitrite ions from foods would oxidize the iron in hemoglobin, destroying its ability to carry oxygen. Tocopherol vitamin E is also an antioxidant. In the body, vitamin E is thought to act by scavenging harmful by-products of metabolism, such as the highly reactive molecular fragments called free radicals. In foods, vitamin E acts to prevent fats from being oxidized and thus becoming rancid. Vitamin C is also a good antioxidant. Finally, and of greatest importance, green plants carry out the redox reaction that makes possible almost all life on Earth. They do this through a process calledphotosynthesis, in which carbon dioxide and water are converted to glucose C6H12O6 . The synthesis of glucose requires a variety of proteins called enzymes and a green pigment called chlorophyll that converts sunlight into chemical energy Figure 5.7 "Life on Earth" . The overall change that occurs is as follows:.