ABSTRACT
This chapter introduces to the idea that lipid and water solubility is a major foundation stone of biochemistry. Cell membranes, being composed mainly of lipids, provide a barrier to the chemicals, and therefore there must be special (bio)chemical mechanisms for the nutrients or signals to pass across the cell membrane. By contrast, the blood also needs to be able to transport lipids or lipid-soluble substances, and again there is a (bio)chemical process that enables this to happen. A cell is more than a lipid bag containing water, it is really an outer lipid bag or cell membrane containing several smaller lipid bags or compartments. In addition to the functions carried out by the subcellular compartments, cells have a particular shape. They can also change their shape and move when required. The shape of a cell and its ability to move comes from a group of structural chemicals called cytoskeletal proteins.
