The glycocalyx serves a variety of functions, from allowing bacteria to adhere to objects to keeping the cornea moist. Glycocalyx is the general name for a gel-like coating that covers the outside of certain cells. The coating is made up of carbohydrates and fibrous proteins.
All bacteria have a glycocalyx, but glycocalyx coatings are also found in certain animal cells. In some bacteria, the glycocalyx may form a tightly bound outer covering called the capsule. The capsule protects the bacterial cell from being consumed by other cells because it covers up molecules used to grab the bacteria and pull it inside an attacking cell. The capsule also makes the bacterial cell sticky, so it can adhere to objects and to other cells. This helps the bacteria form colonies and resist being flushed away by currents.
Animal cells, unlike bacterial cells, do not always have a glycocalyx. In humans, cells with notable glycocalyx coatings are found in certain tissues doing various kinds of work. Within the eye, glycocalyx proteins near the cornea draw water in and keep the cornea moist. This protects the cornea from infection and from exposure to air.
The inner lining of human blood vessels also contains glycocalyx-producing cells. Here, the glycocalyx serves as an interface between blood and blood vessel, regulating the passage of hormones and nutrients to and from organs. It also modulates the number of red blood cells passing through capillaries. Finally, throughout the body, the glycocalyx is used to identify cells as the body's own and to facilitate communication between cells in the same tissue.