Methane, ethane, propane, and gasoline are hydrocarbons. Biological molecules form many types of functional groups , such as those in Fig. These groups and carbon's four bonds allow organic compounds to be very large. Some examples are shown in Fig. 3.3 biological macromolecules These molecules are built by enzymes, proteins that can catalyze reactions.
Sugars are the best-known carbohydrates.
The simplest are monosaccharides , and have four to six carbons and form in a ring. Their sweetness is related to the ring structure. They can also be chained to form starches or cellulose. The two are identical except for the way the sugars are attached. Carbohydrates often contain oxygen, which is a polar or charged atom.