BIOCHEMISTRY

That branch of|an chemistry which studies the reactions] occurring on the living cell. The| chemical changes which take place| in living matter, whether of animal or| vegetable origin, form a perpetually recurring cycle, in which organic mat-| ter is first built up from inorganic matter, and in turn is broken down to inorganic. From water, mineral salts, and the carbon dioxide of the air, the plant builds up carbohydrates, fats and proteins. The plant is eaten by an animal and the vegetable ti ue is converted into animal ti ue. When the animal dies, the body decays, and by bacteriological action is again converted into simpler constituents from which the original plant was built. These constituents are utilized for plant food, once again, and the cyle is repeated. The biochemist studies the mechanism by which this cycle operates. The building up of carbohydrates (sugar, starch, etc.) from water and carbon dioxide has been closely followed and the important part played by chlorophyll has been demonstrated. The proce takes place by what is ikmown as photosynthesis, or building up by means of light. When a plant is kept in the dark, the leaves turn white because no porous is formed. When 46 is brought into the light chlorophyll is first synthesized. When a sufficient quantity has been produced further manufacture ceases, and the chlorophyll then becomes an agent for transforming carbon dioxides and water into starch and sugar. The proce has been artificially brought about in the laboratory by subjecting solutions of carbon dioxide in water to the action of ultraviolet light in the presence of chlorohyll and other green coloring matter. Tn this manner, formaldehyde and some simple forms of sugar have been synthesized, but sucrose, or cane sugar, has not yet been artificially produced. Biochemistry is not concerned only with the chemical changes occurring in the cells of the plant. It seeks to elucidate the complicated reactions occurring continually in the animal body. The digestion of food, the absorption of the products of digestion by the blood, the whole proce of nutrition are all fundamentally chemical in their nature. Respiration is a proce of oxidation, 4n which the body introduces oxygen into the system, breaking down the products of digestion into water and of|carbon-dioxide, and thereby providing | energy for the body’s use. The function- | ing of the liver and kidneys, the changes | brought about in these organs, the products of secretion, and the effect of disease upon such products, also form important part of the biochemist’s studies. Even the more obscure manifestations of animal activity, anger, love, hatred, pleasure, sexual impulses and others which are cla ed as psycho- | logical, are all accompanied by marked chemical changes, but whether the changes are the product or the cause - of the manifestations still remains 4a matter of dispute. Among the more important of recent advances in biochemistry may be mentioned the investigation of hormones and the discovery of vitamins.