The action of the hormone epinephrine on muscle cells in mammals. The hormone's effect on muscle cells is a rise in intracellular glucose concentration providing energy in antissipation of increased mucle activity. This becomes necessary for example when sudden flight seems required. 1. Epinephrine (the first messenger, also called adrenaline) is excreted from specialized cells, carried with the blood stream and eventually arrives at the muscle cells. 2. Here it binds to its specific receptor (Fig. 13.12). The epinephrine receptor belongs to a large family of cell-surface receptors called G protein-coupled receptors . When activated they all transmit their signal via the activation of the small guanosine nucleotide-binding protein called G protein . G protein in its inactive state has bound a GDP. The activated epinephrine receptor exchanges the GDP in the G protein for a GTP. This causes the G protein to undergo transformation into its active state. 3. In muscle cells (Fig. 13.11) the
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This document was uploaded on 11/03/2011 for the course BIOLOGY MCB2010 at Broward College.