Oestrogen is a steroid hormone that plays a key role in the menstrual cycle. How is oestrogen transported through the blood to the cells of the endometrium, and how does it enter these target cells to initiate transcription?
Transported dissolved directly in the blood plasma; it enters target cells by facilitated diffusion through channel proteins.
Transported bound to carrier proteins in the blood plasma; it enters target cells by simple diffusion directly through the phospholipid bilayer.
Transported inside the cytoplasm of red blood cells; it enters target cells by active transport using ATP-driven carrier proteins.
Transported via the lymphatic system; it enters target cells by endocytosis (pinocytosis) of the hormone-receptor complex.
