Cellular component refers to the unique, highly organized substances of which cells, and thus living organisms, are composed.Cells are the structural and functional units of life. The smallest organisms are composed of only a single cell while the largest are made up of billions of cells. DNA is found in nearly all living cells, however each Cell consists of its own unique DNA sequence in its chromosome. Examples include membranes, organelles, proteins, and nucleic acids. Whilst the majority of cellular components are located within the cell itself, some may exist in extracellular areas of an organism.