Membrane Carbohydrates—The Cell “Glycocalyx.”

 Membrane Carbohydrates—The Cell “Glycocalyx.”

 Membrane  carbohydrates occur  almost  invariably in  combination with proteins or lipids in the form of glycoprotein  or  glycolipids,  the entire outside surface of the cell often has a loose carbohydrate coat called the glycocalyx. The carbohydrate  moieties attached to

the outer surface of the cell have several important functions:

(1) Many of them have a negative electrical charge, which gives most cells an overall negative surface charge that repels other negative objects. (2) The glycocalyx  of some cells attaches to the glycocalyx of other cells, thus attaching cells to one another.

(3) Many of the carbohydrates act as receptor substances for binding hormones, such as insulin.

(4) Some carbohydrate moieties enter into immune reactions.