Figure 8-1 Complex Molecules and Carbon (a) Atoms that can bond to only two other atoms, like the atoms denoted X shown here, can form a chain of atoms called a linear molecule. The chain stops where we introduce an atom, such as those labeled Y and Z that can bond to only one other atom. (b) A carbon atom (denoted C) can bond with up to four other atoms. Hence, carbon atoms can form more complex, nonlinear molecules like glucose. All organic molecules that are found in living organisms have backbones of carbon atoms.