The smallest complete unit of a substance that can exist independently and still retain the characteristic properties of that substance. Almost all molecules consist of 2 or more atoms that are bonded together. Molecules that consist of only one atom are known as monatomic molecules.
The smallest possible amount of a substance comprising two or more linked atoms which retains the chemical characteristics of that substance. Molecules vary greatly in their size and complexity, ranging from oxygen (two linked oxygen atoms) and water (two hydrogen atoms and one oxygen) to large complex molecules such as deoxyribonucleic acid (DNA) comprising thousands of atoms of carbon, hydrogen, oxygen, nitrogen and phosphorus that form the double-helix structure which helps to form GENES, the basic building blocks of the hereditary material of living things.
molecules on the surface of cell membranes that are responsible for most cellular functions directly related to their immediate environment. Many have very precise functions of adhesion (see adhesion molecules), metabolic exchange, hormone reception, respiration, and immune reactions. Cell-to-cell exchanges involve specialized surface structures (junctions), which form a communicating nexus.... cell-surface molecules
Health Encyclopedia