Molecules of Life
Molecules of life are classified as - carbohydrates, Lipids, proteins and nucleic Acids. 20 to 25 percent of living matter consist of these macromolecules.
Water, inorganic ions and a large array of relatively small organic molecules (e.g. sugars, vitamins, fatty acids) account for 75−80 percent of living matter by weight. Of these small molecules, water is by far the most abundant. Each type of small molecule has unique properties arising from the orderly arrangement of its atoms. Small organic molecules are joined inside cells, forming larger molecules called macromolecules.
The four main classes of large biological molecules are carbohydrates, lipids, proteins and nucleic acids. 20−25 percent of living matter consists of macromolecules, including proteins, polysaccharides and DNA. Though all of these groups are organized around carbon, each group has its own special structure and function. Cells acquire and use these macromolecules in fundamentally different ways.
Ions, water and many small organic molecules are imported into the cell. Cells also make and alter many small organic molecules by a series of different chemical reactions. In contrast, cells can obtain macromolecules only by making them. Their synthesis entails linking together a specific set of small molecules (monomers) to form polymers through repetition of a single type of chemical−linkage reaction.