a. Local signaling is when cells communicate in direct contact like through cell junctions that allow molecules to pass readily between adjacent cells without crossing plasma membranes or cell to cell recognition where two cells communication by interaction between molecules protruding from their surfaces. Long distance signaling is communication without direct contact like the release of hormones into the circulatory system to other parts of the body where they can reach the target cells throughout out the body that can respond to the hormone without direct contact. In both local and long distance signaling, only specific target cells that can recognized a given signaling molecule will respond to it. The two specific type of local signaling is paracrine signaling and synaptic signaling. Paracrine signaling is when the messenger cell secretes messenger molecules that travel only short distance called local regulations into the extracellular fluid to influence cells close by. On the other hand, synaptic signaling happens in the animal nervous systems. An electrical signal along a nerve cell triggers the secretion of neurotransmitter molecules carrying a chemical signal which will diffuse across the synapse (narrow space between nerve cells and its target cells) to trigger a response in target cell.
b. Cell signaling is specific means that the ability of a cell to respond is determined by the specific receptor molecule that can bind to the signaling. So a signal can only affect the target cells that contains that receptor to bind to the signal and none other, making cell signals to be effective only to selective target cells to trigger specific effects and not affecting other cells.
c. The three parts of cell signaling is reception, transduction and response. Reception is the target cell's detection of a signaling molecule coming form the outside of the cell. The signal can be detected when the signaling molecule binds to a receptor protein...
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