Final answer:
Antioxidants are substances that protect cells from damage caused by free radicals, which are unstable molecules produced by the body. They include vitamins A, C, E, beta-carotene, and selenium, and can act both within the body and as food additives to preserve food by preventing oxidation.
Step-by-step explanation:
Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a reaction to environmental and other pressures. Antioxidant defense mechanisms, such as detoxification within the peroxisome, are essential for neutralizing these potentially harmful molecules. Important dietary antioxidants include vitamins C and E, beta-carotene, and selenium, which are found primarily in fruits and vegetables.
Vitamins as Antioxidants: The 'big three' vitamin antioxidants are vitamins E, A, and C. They work by being oxidized themselves, which halts the destructive reaction cascades initiated by free radicals. For instance, vitamin C (ascorbic acid) can reduce potentially damaging oxidation of living cells by being oxidized to dehydroascorbic acid, while vitamin E (tocopherol) acts to prevent fats from becoming rancid due to oxidation.
Some antioxidants, such as Vitamin A and E, work locally in specific regions of the body, whereas others like selenium and vitamin C have a more global effect. In addition to their roles within the body, antioxidants like ascorbic acid and tocopherols are also used as food additives to preserve the quality and extend the shelf life of foodstuffs by protecting them against oxidation.