List the major steps of the cAMP, cGMP and IP3 path. Discuss the key parts of a simple endocrine system. Explain why the same hormone may have different responses at different cells or no response at all. Discuss the importance of Calcium as a second messenger. Introduction We now turn from the single cell environment to multicellular communication.
Multicellular interaction is evident even in typically independent unicellular organisms.
Yeast, for example, signal each other specifically during mating cycles. Within the cells of animals, communication is via hundreds of signaling molecules including proteins, peptides and amino acids, nucleotides and even dissolved gases such as nitric oxide and carbon dioxide. These signals, interpreted by complex cellular machinery, enables the cell to determine its specialized position and role within the 75 trillion cell human body. The resulting cancer may well be incompatible with the life. It was another billion years before the fossil record shows any sign of multicellular life.