Signal transduction pathways

Topic Description

A) you can see here, the epinephrine binds to a protein receptor called B adrenergic receptor protein on the membrane of a liver cell. A)The receptor then changes shape and activates a specific membrane protein called a G-protein receptor because it binds to guanine nucleotides such as GTP. G-proteins are like a molecular switch that can turn on a chemical pathway. When the G-protein is activated it in turn activates the enzyme adenylyl cyclase. This then triggers the process of transduction. A)Notice that adenylyl cyclase begins the process of transduction by converting ATP to cyclic AMP. Cyclic AMP, which is often abbreviated as cAMP, is a modified ATP molecule that only has one phosphate group. cAMP is called a second messenger because it takes the message from the signal molecule epinephrine in to the cell. Many cyclic AMP molecules may be produced at once. This process is called amplification because one signal molecule may trigger a cascade of reactions in the cell. This will allow many molecules of glycogen to be broken down as the result of one molecule of epinephrine binding to the liver cell. As you can see, the Cyclic AMP molecules will now activate protein kinase molecules. Protein kinases are enzyme that have the ability to phosphorylate, And therefore provide energy to, other molecules. In our example, protein kinase will phosphorylate the enzyme glycogen phosphorylase that will break the covalent bonds within glycogen so that a lot of glucose molecules can be released quickly by your liver cells. This is the response part of the signal transduction pathway. The glucose can then travel through your bloodstream so that your brain and muscles have the necessary quick energy to help your body respond to your first Skydiving experience and you can land safely