Overview of transport proteins in eukaryotes.

             One of the most integral building blocks of life is the transport protein. These proteins can be found in the membranes of cells and their subcellular organelles, and are responsible for facilitating some of the most essential physiological processes. All of the information regarding transport proteins in this overview was found in Molecular Cell Biology 3rd Ed. by Lodish et al. (1995). .

             Some of the processes transport membranes enable cells to carry out include maintaining cytosolic pH, transporting glucose across the intestinal epithelium, the accumulation of sucrose and salts in plant-cell vacuoles and the directed flow of water in both plants and animals. Transport proteins in differing combinations can allow for a wide variety functions, so each type of transport protein can be used for very different purposes. .

             There are three major types of transport proteins that are found in membranes, ATP powered pumps, channel proteins, and transporters. ATP powered pumps are ATPases. They use ATP hydrolysis to move ions across a membrane against their concentration gradient. Channel proteins open for ions to cross the membrane down their concentration gradient, and can be gated. Transporters can change their structure in order for molecules to pass through. These can work both along a concentration gradient, as uniporters, and against a concentration gradient, as symporters and antiporters.

             ATP powered pumps can be divided into three classes, P, V and F. It is the V class that maintains the low pH level in plant vacuoles, lysosomes and in some vesicles in animal cells. It does so by using the energy made available from the ATP hydrolysis to pump protons up the electrochemical gradient and to the exoplasmic side of the membrane. This is just one example of how protein pumps play an active role eukaryotic cells. The jobs these, and the other types of transport proteins do, enables life to proceed efficiently.