Early in his presidency, Theodore Roosevelt sparked a scandal when he invited the African-American educator Booker T. Washington to dine with him and his family; he was the first president ever to entertain a black man in the White House. In 1886, Roosevelt ran unsuccessfully for mayor of New York City. Two years later, President Benjamin Harrison rewarded Rooseveltâs service to the Republican Party with a job on the U.S. Civil Service Commission; he was reappointed by Harrisonâs successor, Grover Cleveland.
1 Signaling involves a receptor, the transduction of information from the cell surface to inside the cell, and subcellular systems that make a response. 2  Receptors are proteins with specific binding sites for signaling molecules called ligands. All cells are equipped with elaborate systems for receiving signals from their environment. 2  The mechanisms involved in cell signaling are particularly crucial for understanding multi-cellular organisms, and are an important in many diseases.
Signal transduction occurs when an extracellular signaling molecule activates a specific receptor located on the cell surface or inside the cell.In turn, this receptor triggers a biochemical chain of events inside the cell, creating a response.Depending on the cell, the response alters the cell's metabolism, shape, gene expression, or ability to divide. The signal can be amplified at any step. Thus, one signaling molecule can cause many responses.his may occur independent of signal transduction stimulation by other molecules, as is the case for the toll-like receptor. It may occur with help from stimulatory molecules located at the cell surface of other cells, as with T-cell receptor signaling.