Answer to Question 1
d
Answer to Question 2
Antioxidant vitamins include vitamin C, vitamin E, and beta-carotene. Antioxidants are compounds that protect other compounds (such as lipids in cell membranes) from attack by oxygen. Oxygen triggers the formation of compounds known as free radicals that can start chain reactions in cell membranes. Vitamin E and beta-carotene protect fat-soluble substances from oxidizing agents; vitamin C protects water-soluble substances the same way. By being oxidized itself, vitamin C regenerates already-oxidized substances such as iron and copper to their original, active form. In the intestines, it protects iron from oxidation and so enhances iron absorption. In the cells and body fluids, it helps to protect other molecules, including the fat-soluble compounds vitamin A, vitamin E, and the polyunsaturated fatty acids.
Like beta-carotene, vitamin E is a fat-soluble antioxidant. It protects other substances from oxidation by being oxidized itself. If there is plenty of vitamin E in the membranes of cells exposed to an oxidant, chances are this vitamin will take the brunt of any oxidative attack, protecting the lipids and other vulnerable components of the membranes. Vitamin E is especially effective in preventing the oxidation of the polyunsaturated fatty acids (PUFA), but it protects all other lipids (for example, vitamin A) as well.
Primary production is positively correlated with the evapotranspiration rate.
Cast of Isotelus rex, the largest known trilobite from the middle to upper Ordovician of North Ameri
Map of Mars from Hubble Space Telescope as seen near the 1999 opposition. (North top)
Researchers have found that science instruction can be quite effective in grades 4 to 7.
Factors That Affect Your Basal Metabolic Rate
Elephant herd drinking at water hole. Botswana