Carbon compounds that come from living organisms include carbon dioxide, carbohydrates and hydrocarbons. Organic chemistry is the study of carbon compounds, many of which are necessary for life.
Carbohydrates are abundant in foods made from living things, such as bread, milk and cereals. Plants are largely made out of carbohydrates. Carbohydrates are compounds that are made of carbon, hydrogen and oxygen. Some of these molecules are small, such as those that make up simple sugars. Others come in long, complex chains, such as those that make up starches. Carbohydrates are easily digested by human beings and serve as fuel for the body.
Animals also inhale oxygen and exhale carbon dioxide as a waste product. Plants take in carbon dioxide and release oxygen as a waste product.
Hydrocarbons are molecules made of hydrogen and carbon. Many fossil fuels are hydrocarbons, including natural gas, crude oil and coal. These are created over millions of years from dead plants and animals. Peat is also a fuel made from vegetative matter.
The edible oils, such as fish oil and vegetable oil, are also types of hydrocarbons.
Seashells are made of calcium carbonate, and much of the limestone used in building and other industries comes from crushed and pulverized seashells.