1. (Biochemistry) the sum total of the chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material, etc. 2. (Biochemistry) the sum total of the chemical processes affecting a particular substance in the body: carbohydrate metabolism; iodine metabolism.
It is found only in cultivation, where it is the most commonly grown of all plants in the Nicotiana genus, and its leaves are commercially grown in many countries to be processed into tobacco.It grows to heights between 1 to 2 metres.he concentration of nicotine increases with the age of the plant. Tobacco leaves contain 2 to 8% nicotine combined as malate or citrate. The distribution of the nicotine in the mature plant is widely variable: 64% of the total nicotine exists in the leaves, 18% in the stem, 13% in the root, and 5% in the flowers.
What's in a Cigarette & Disease: Chemicals, Cancer and Heart Disease. The main ingredient in cigarettes is tobacco. Tobacco is a green, leafy plant that is grown in warm climates. Farmers use many chemicals to grow tobacco. They use fertilizers to make the soil rich and insecticides to kill the insects that eat the tobacco plant. After the tobacco plants are picked, they are dried, and machines break up the leaves into small pieces.