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.
An activation barrier, representing the transition state
Rate enhancement by entropy reduction
Some of the many small molecules found in cells
Situations Causing Changes in Respiratory Rate
Arctic Oscillation and North Atlantic Oscillation
The basic structure of an antibody molecule. Two heavy chains are joined by two light chains. The ...