Cell Biology
The word cell comes from the latin cellula, meaning, a small room. The descriptive name for the smallest living biological structure was chosen by Robert Hooke in a book he published in 1665 when he compared the cork cells he saw through his microscope to the small rooms monks lived in. A cell is the fundamental, structural, and functional unit of living organisms. All cells contain certain types of complex chemicals components: Proteins, Nucleic acids, lipids and polysaccharides. Collectively, these are called macromolecules. Because these chemical components are common throughout the living world. It is thought that all cells have descended from a single common ancestor, the universal ancestor. Each cell is at least somewhat self-contained and self-maintaining: it can take in nutrients, convert these nutrients into energy, carry out specialized functions, and reproduce as necessary. Each cell stores its own set of instructions for carrying out each of these activities
We may distinguish two general types of cells:
- Bacteria are the Prokaryotes, organisms in which nominally there is only a single cell compartment, bounded by a membrane or membranes that give security against the outside world ( Prokaryote cells DO NOT have a cell membrane around their nucleus). There are two kinds of prokaryotes, bacteria and archaea, but these are similar in the overall structures of their cells
- Eukaryotes are defined by the division of each cell into a nucleus that contains the genetic material, surrounded by a cytoplasm which in turn is bounded by the plasma membrane that marks the periphery of the cell. The cytoplasm contains other discrete compartments, also bounded by membranes. Eukaryotic cells usually are 10 times larger than Prokaryotic cells.
These two types of cells are structurally very different. A major structural difference between prokaryotes and eukaryotes, other than size is the arrangement of DNA within the cell. Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.
References:
- Garrett and Grisham. BIOCHEMISTRY. Saunders College Publishing. Harcourt Brace College Publishers
- M.T. Madigan et al. Biology of Microorganisms. Prentice Hall. International Inc