Naturally occurring polymers include the macromolecules that can be found in the human body. These macromolecules, or biopolymers, include lipids, polysaccharides, proteins, and nucleic acids.
What these biopolymers have in common is that they are all composed of monomers that have one or more carbon atoms joined with covalent bonds to other carbon atoms, or to hydrogen and oxygen atoms.
Carbon Bonding
Because of the hybridization of its bonding orbitals, carbon's outermost three p-orbitals and one s-orbital are combined to give four equivalent sp3 -orbitals.
Carbon orbital hybridization has the result that each carbon atom can form four covalent bonds. When carbon is covalently bonded to four equivalent atoms, the shape of the molecule is a tetrahedron.