Cellular Transport

There are several types of transport that are used to shuttle the substances so vital to life in the biological cell used in animals and plants. These accomplish a myriad of tasks, ranging from simple movement of substances needed to survive, to the balancing of compounds to keep the cell in a stable environment.

Three types of cellular transport exists, and are utlized by the cell with respect to its selectively permeable phospholipid bilayer. Paswsive diffusion is the simple movement of substances through the principle of diffusion. It occurs straight on through the phospolipid bilayer, with substances moving from a region of higher concentration to a lower concentration, down their concentration gradient. The principle of osmosis comes into play with this as well, with water traveling from areas of lower solute concentration (more water) to locations of higher solute concentration (less water).

The second type of transport to be discussed here is facilitated transport. Here, this process, also known as passive transport, occurs when carrier molecules, often embedded proteins, assist substances in moving down their gradient from higher to lower concentration graident.

Both passive and facilitated diffusion fall under the category of passive transport, as no energy (ATP) is required to cause this to occur. Both are also passive in the sense that they occur down, and not against, their gradients. Thus, they both are passive types of transport, one simply the following the flow of a natural process, the other utilizing a carrier molecule to help assist in the process of diffusion and osmosis.

Finally, the last type of transport is active transport. Here, substances are carried against their concentration gradient, with the help of a carrier substance or molecule. Unlike the previous two types of transport, this does require energy, as the substance that is to be moved is being moved against the natural flow of diffusion and osmosis. Proteins are often the type of carrier molucule used to accomplish this feat, and this transport is often used to keep the important membrane potential in some cell.