Describe the differences between hydrophobic and hydrophilic signalling.

Hydrophobic signalling molecules can pass through the lipid bilayer of the membrane due to both being hydrphobic. Once within the cell, the molecule can bind to a receptor or transcription factor to inhibit or enable transcription. Hydrophilic signalling molecules cannot pass through the membrane, instead they must bind to receptors on the extracellular side of the cell membrane. These receptors can be ligand gated channels which open when the molecule binds or they can be G-coupled protein receptors which change shape slightly when the signal binds thus releasing another molecule within the cell which can then bind to a transcription factor like with hydrophibic signalling or can open other channels.