Biology Chapter 11

-messengers secreted by the signaling cell-these travel only short distances-influence cells in the vicinity -one class is growth factors

-class of local regulators-consist of targets that influence nearby cells to grow and divide

-type of local signaling in animals

-more specialized type of local signaling-happens in animal nervous system-electrical signal along

-both animals and plants use these chemicals for long distance signaling -endocrine signaling-travel via the circulatory system to target cells in other parts of the body

-sometimes travel in vessels but more often reach their targets by moving through cells or diffusing through air as a gas

-when a cell encounters a molecule the molecule must be recognized by a specific receptor molecule and the signal must be changed into another form

-Sutherland's team discovered that epinephrine stimulates glycogen breakdown by somehow activating a cytosolic enzyme, glycogen phosphorylase-epinephrine can only activate glycogen phosphorylase when the hormone was added to a solution containing intact cells-epinephrine does not interact directly with the enzyme responsible for glycogen breakdown-plasma membrane is somehow involved in transmitting the epinephrine signal-reception, transduction, response

-target of cell's detection of a signaling molecule coming from outside the cell-chemical signal detected when the signaling molecule binds to a receptor protein located at the cell's surface or inside cell

-binding of the signaling molecule changes receptor protein in some way, initiating process of transduction-transduction stage converts signal to a form that can bring about a specific cellular response-sometimes occurs in a single step, but more often in a sequence of changes in a series of different molecules (signal transduction pathway)--uses relay molecules

-transduced signal finally triggers a specific cellular response -response may be almost any cellular activity, such as catalysis by an enzyme, rearrangement of the cytoskeleton, activation of specific genes in nucleus-helps ensure that crucial activities occur in the right cells at the right time and in coordination

-only certain cells detect and react to hormone -receptor protein allows cell to hear the signal and respond to it-key in a lock or substrate in catalytic site of any enzyme-signaling molecule behaves as a ligand--molecule that specifically binds to another molecule, often a larger one-most signal receptors are plasma membrane proteins w/ water soluble ligands too large to pass through plasma membrane-some receptors inside the cell

-molecule that specifically binds to another molecule, often a larger one-causes a receptor protein to undergo a change in shape -shape change directly activates the receptor, enabling it to interact with other cellular molecules -for some receptors, immediate effect of ligand binding is to cause the aggregation of two or more receptor molecules, which leads to further molecular events

-similar to allosteric binding to an enzyme-alters ability of receptor to transmit the signal

-in cytoplasm or nucleus of target cells-chemical messenger passes through target cell's plasma membrane--signaling molecules that are hydrophobic or small enough to cross phospholipid interior of membrane -steroid, thyroid, nitric oxide,