Could someone explain the complete process of how a lipophilic hormone (steroid) enters a cell and thus signals the cell to carry out a response?
Conversely could someone also explain in contrast how a Hyrdophillic hormone (amino acid/peptide) accomplishes the same thing?
Much appreciated.
You don't really need to know these things exactly, but the basic mechanisms.
LipophillicMakes its way through the membrane and into the cell where it associates with a chaperone. This chaperone brings it into the nucleus, where it acts in a biochemical pathway that up regulates or down regulates transcription. In general, lipophillic hormones act as transcription factors.
HydrophillicBinds to a receptor on the membrane. These can be a number of different types.
If the receptor is attached to a protein channel, this can cause an influx or outflux of ions. Neurotransmitters are an example of this.
The receptor can also be a G-protein, which undergoes a conformational change and interacts with a secondary messenger that amplifies the signal in the cell. Essentially, that one binding causes the transmembrane protein to stimulate heaps of proteins in the cell so the biochemical effect of the signalling is amplified. That's the signal cascade.
Those are fairly basic concepts, but that should be well more than enough.