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Nicotine molecules are made up of carbon, hydrogen, nitrogen and sometimes oxygen.

Nicotine (C10H14N2) is a naturally occurring liquid alkaloid. An alkaloid is an organic compound made out of carbon, hydrogen, nitrogen and sometimes oxygen. These chemicals have potent effects on the human body. For example, many people regularly enjoy the stimulating effects of another alkaloid, caffeine, as they quaff a cup or two of coffee in the morning.

Nicotine normally makes up about 5 percent of a tobacco plant, by weight. Cigarettes contain 8 to 20 milligrams (mg) of nicotine (depending on the brand), but only approximately 1 mg is actually absorbed by your body when you smoke a cigarette.