Released from carrier protein to diffuse across cell

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Unformatted text preview: Released from carrier protein to diffuse across cell membrane into target cells. Act by binding to intracellular protein receptors . Signal transduction pathways via second messengers Act as cofactors/coenzymes to modulate intracellular enzyme activity Signal molecule ( first messenger ) – Do not enter target cells. Act as ligand by binding to protein receptor on cell surface. 1. Since the signal molecule (first messenger) does not enter the cell, the receptor/ ligand complex causes a second messenger to be produced or released within the cell. 2. This second messenger acts as a coenzyme/cofactor to regulate cellular enzymes fi change the activity of the cell. Heyer Receptor Activated relay molecule ( second messenger ) Inactive enzyme Active enzyme 2 Coordination of Body Functions Intracellular Receptors for Lipophilic Signal Molecules 1. Steroid diffuses across membrane into cell 2. Intracellular receptor/steroid complex binds to DNA 3. Transcription factor — turns genes on/off 4....
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