A chemical compound is a molecule that consists of two or more than two different atoms combined in a fixed proportion. For example water is a chemical compound consisting of two atoms of hydrogen chemically combined with one atom of oxygen.
Chemical compounds can be classified into two broad groups, organic and inorganic compounds. Inorganic compounds are relatively simple, small compounds such as water, salt, simple acid like hydrochloric acid, and simple base like ammonia. These substances are required for fluid balance and for many activities of cell such as transporting materials through the cell membrane. Organic compounds are large, complex compounds containing carbon. These are the chemical building blocks of the body and also serve as fuel molecules that provide energy for body activities. Organic compounds also regulate and participate in thousands of chemical reactions necessary for life.
Four important group of organic compounds are carbohydrates, lipids, proteins, and nucleic acid.
- Carbohydrates are sugars and starches. They are used as fuel by the body and to store energy. Glucose is a simple sugar that is a main source of energy for the body. The liver and muscles can link glucose molecule into long chains, producing glycogen, a large molecule that can be stored.
- Lipids include fats, compounds that store energy; phospholipids, which are components of cell membrane; and steroids, which include several hormones.
- Proteins are complex, and large compounds composed of subunits called amino acids. Some proteins serve as enzymes, catalyst that regulate chemical reactions. Other proteins are the structural components of cells and tissues. The kind and amount of proteins in a cell determine to a large extent what a cell looks like and how it functions. For example, muscle cells have large amounts of the proteins myosin and actin, which are responsible for their appearance and their ability to work.
- Nucleic acid are also large and complex compounds. Two very important nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) . DNA makes up genes (the hereditary material) . It contains the instructions for making all the proteins needed by the cell. RNA is important in the process of manufacturing proteins.