The Cell


  • The cell is the basic functional unit of the body's organs.
  • It can be divided into three principal parts:


Cell Membrane: The selectively permeable cell membrane surrounds the cell, gives it form and separates the internal structures fromthe extracellular environment.


Cytoplasm and Organelles: Cytoplasm is the aqueous content of the cell and the cell contents except the nucleus.


Nucleus: Is a large spheroidal largest organelle of the cell. The nucleus contains the majoprity of the genetic information for the production of the proteins produced by the cell.


The Cell Membrane
  • The cell membrane is a semipermeable membrane that acts as a barrier between the external environment and the internal environment of the cell.
  • It is composed of a bilipid layer of phospholipids. These orient themselves in such a way that the hydrophobic ends are withinthe internal part of the bilipid structure.
  • Apart from the phospholipids, a number of proteins are also found in the cell membrane. Some proteins are found partially submerged on each side of the membrane, whilst others span the membrane.
  • Proteins and lipiods are free to move accross the membrane and hence the strucutre is called the fluid-mosaic model.
  • The proteins found in the cell membrane have various functions including support, transport of molecules, signalling and enzymatic actions.
  • In addition to lipids and proteins, the cell membrane has a number of carbohydrates atatched either to the phospholipids (glycolipids) opr ot the proteins (glycoproteins). These carbohydrates act as signalling structures between cells.
  • Another important aspect of the cell membrane is the fact that it can act as a semipermeable membrane. A semi-permeable membrane, as the name implies, is a membrane that is permeable to some solutes but not to others. Osmosis and osmotic pressure is an important aspect of semi-permable membranes.