Cytoplasm 多 B lood plasma Triiodothyronine Plasma membrane Receptor mRNA nuClEUs FIGURE 53.6 The mechanism of thyroxine action. Thyroxine contains four iodines. When it enters the target cell, thyroxine is changed into triiodothyronine, with three iodines. This hormone moves into the nucleus and hinds to nuclear receptors. The hormone-receptor mplex then binds to regions of the DNA and stimulates gene transcription
Introduction hormon New Ribosome RNA Nucleus mRNA Hormone-receptc DNA complex Steroid hormones act in a very different way than peptides. Since they are fat-soluble, they can cross the membranes of their target cells. They bind to receptors in the cytoplasm or nucleus and the hormone-receptor complex triggers transcription of certain gen