Cell membrane Proteins

In the cell membrane, there are a wide composition of proteins present. The most common protein you'll find in the membranes are receptors and channels. They are the messenger of cells. Receptor senses whats going on outside the cells and sends signal down to adjust accordingly. On the other hand, channels are like doors for your cells. They allow passage of nutrients and biochemicals. The most common type of channels you might find in a cell are aquaporins. The clever amongst you may have already realised what this channel/transporter do. It allows movement of water molecule through the membrane. Whilst water is a polar molecule and can move through the membrane bi-layer, it predominately uses this transporter for efficient and fast transport of water molecules. Down below is an actual X-ray crystallography picture of aquaporin channel.

This is a top down view of the channel. Its made up of four sub-units.