Organic Molecules of Life

Living systems are composed of various types of molecules. There are two main types: Organic and Inorganic molecules. All organic molecules contain carbon and those that don't are classified as Inorganic molecules. Organisms maintain reserves of small organic molecules that they can assemble into complex Macromolecules such as carbohydrates, lipids, proteins, and nucleic acids. These are the building blocks of the living organisms.

How are macromolecules formed?

Small molecules common to all organisms are ordered into unique macromolecules.
Many macromolecules consist of polymers. A polymer is a large molecule built up from smaller building block molecules, called monomers. Monomers (subunits) are the building block molecules. The inherent differences between human siblings reflect variations in polymers, particularly DNA and proteins. Macromolecules that make up living organisms are formed via polymerization.
Polymerization is the linking together of monomers to form polymers. Large organic molecules are often built from smaller ones by condensation, a process in which an enzyme covalently bonds two molecules together. A condensation reaction occurs via the loss of a small molecule, usually from two different substances, resulting in the formation of a bond. Polymerization in biological systems typical occurs via dehydration synthesis. Dehydration reaction is synonymous with condensation reaction except that dehydration reaction is limited to those condensations in which the small molecule is water. Dehydration synthesis is synonymous with dehydration reaction.

 

 Figure: Condensation reaction. Three boxes represent molecules attached to each other that have free hydrogen and hydroxyl group. These groups can be utilized to form a bond via dehydration reaction, removing H2O.

Energy is expended to polymerize so all condensation/dehydration reactions require an input of energy in order to move forward!!! Energy is expended to make polymers!