 Each of these types of biomolecules are polymers that are assembled from single units called monomers.

Biomolecule Carbohydrates Lipids Proteins Nucleic acids Monomer ( building blocks) Monosaccharide Not always polymers; Hydrocarbon chains Amino acids Nucleotides

In condensation reactions (also called  dehydration reaction), a molecule water is removed from two monomers and they are connected together.

Strengths of Bonds Common in Biomolecules

Versatility of carbon bonding. Carbon can form covalent single, double, and triple bonds (in red), particularly with other carbon atoms. Triple bonds are rare in biomolecules.

- The four single bonds that can be formed by a carbon atom are arranged tetrahedrally, with an angle of about between any two bonds (Fig.) and an average length of nm. - There is free rotation around each single bond, unless very large or highly charged groups are attached to both carbon atoms, in which case rotation may be restricted. - A double bond is shorter (about nm) and rigid and allows little rotation about its axis. - Thus organic molecules with many single bonds can assume a number of different shapes, called conformation, depending on the degree to which each single bond is rotated.

Geometry of carbon bonding. (a) Carbon atoms have a characteristic tetrahedral arrangement of their four single bonds. (b) Carbon–carbon single bonds have freedom of rotation, as shown for the compound ethane (CH3OCH3). (c) Double bonds are shorter and do not allow free rotation. The two doubly bonded carbons and the atoms designated A, B, X, and Y all lie in the same rigid plane.

To these carbon skeletons are added groups of other atoms, called functional groups, which confer specific chemical properties on the molecule. In the following figure : R is used to represent “any substituent.” It may be as simple as a hydrogen atom, but typically it is a carbon-containing moiety. When two or more substituents are shown in a molecule, we designate them R1, R2, and so forth.