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.
Extracellular molecules such as: hormones; neurotransmitters; cytokines; growth factors; cell recognition molecules; nutrients; or waste products; all react with the archetypical receptor to induce changes in the metabolism and activity of a cell.he seven-transmembrane Î±-helix structure of a G-protein-coupled receptor. Cell surface receptors (membrane receptors, transmembrane receptors) are specialized integral membrane proteins which communicate signals between the cell and the outside world.