Cell membranes

Cell membranes

• The membrane is made up of a 'sea' of phospholipids with protein molecules 'floating' in between the phospholipids. Some of these proteins span the whole width of the membrane.Because the membrane is fluid, and because of the mosaic arrangement of the protein molecules, the structure of the membrane is called the fluid mosaic model.
• All cells in nature are surrounded by Biological Membranes, which all have the same basic structure. Some organelles found in Eukaryotic Cells also have membranes.
• Membranes separate their contents from the environment and organelle membranes separate the organelle contents from their environment.
• Membranes regulate the movement of materials through them. For example, cell membranes might not allow starch molecules to leave the cell.
• Cell membranes are also involved in cell communication and recognition, and in holding some components of metabolic reactions in place.

• Phospholipids - arranged in two layers (a bilayer); the phosphate heads are polar molecules and so are water-soluble. The lipid tails are non-polar and not water-soluble. This means that the phospholipids are arranged with the heads in contact with the cytoplasm or extra-cellular fluid, both of which are watery environments. The…