The processing requirements include successful completion of: 1  The application process, which includes a background and polygraph examination, a medical examination, a physical fitness evaluation, and a written examination; 2  24-26 weeks of intensive Academy training.
The cell membrane, being exposed to the outside environment, is an important site of cell-cell communication. As such, a large variety of protein receptors and identification proteins, such as antigens, are present on the surface of the membrane.
cell. How can a cell make sense of all these signals? Cells have receptors. A receptor is a protein that detects a signal and acts because of it. Only certain molecules will bind to a receptor. A cell responds to a signal only if it has a receptor for that signal. When a receptor binds to a signal, it changes shape. As a result,