'The structure and role of proteins in cell membranes.'

The first 200 words of this essay...

'The structure and role of proteins in cell membranes.'

Cells are the building blocks of which all living organisms are composed. There are lots of different types of cells that make up living organisms but they are all similar in structure. All cells are surrounded by a cell membrane (or plasma membrane), which controls the movement of substances into and out of the cell. Cell membranes are described as partially permeable. It is also structural and keeps the cell contents together and separate from other cells. Furthermore it allows communication between cells and allows recognition of other external substances. Membranes that surround cell organelles are also very similar to the cell membrane. Membranes are composed of phospholipids, which form the bulk of the membrane, proteins, which are scattered around in the membrane. There may also be some molecules of carbohydrates and cholesterol present.

Phospholipids are a special type of lipid. Phospholipids have two fatty acid chains; these form a tail, which is hydrophobic. Fatty acid tails do not have a charge, so they are non-polar and insoluble in water. The phosphate group (head of the phospholipids) is hydrophilic because it has a positive charge and