(a) This molecule of stearic acid has a long chain of carbon atoms. The simplest organic carbon molecule is methane (CH 4), in which four hydrogen atoms bind to a carbon atom ( Figure 2.13).įigure 2.14 These examples show three molecules (found in living organisms) that contain carbon atoms bonded in various ways to other carbon atoms and the atoms of other elements. Therefore, it can form four covalent bonds with other atoms or molecules.

Carbon BondingĬarbon contains four electrons in its outer shell. It is the bonding properties of carbon atoms that are responsible for its important role. Other elements play important roles in biological molecules, but carbon certainly qualifies as the “foundation” element for molecules in living things. It is often said that life is “carbon-based.” This means that carbon atoms, bonded to other carbon atoms or other elements, form the fundamental components of many, if not most, of the molecules found uniquely in living things.

In addition, they may contain hydrogen, oxygen, nitrogen, phosphorus, sulfur, and additional minor elements. Biological macromolecules are organic, meaning that they contain carbon (with some exceptions, like carbon dioxide). Combined, these molecules make up the majority of a cell’s dry mass. There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids), and each is an important component of the cell and performs a wide array of functions. The large molecules necessary for life that are built from smaller organic molecules are called biological macromolecules.

Understand the functions of the four major types of molecules.

Describe the four major types of biological molecules.

Explain the impact of slight changes in amino acids on organisms.

Describe the ways in which carbon is critical to life.

Learning Objectives By the end of this section, you will be able to:

Fwsim 2.3 key