Cells signal to each other to survive, even bacteria.
Target Cell: The cell that is being communicated to.
Ligand: The signal
Receptor: The thing that receives the signal and gives it to the target cell.
Autocrine (auto = self):
A cell communicates with itself 🙁
Paracrine (para = nearby):
Nearby cells are communicated with.
Juxtracrine (juxta = beside, next to, touching):
Touching cells communicate.
Endocrine (endo = within):
Usually, the ligand travels through the bloodstream
There are many different kinds of ligands and receptors:
Certain ligands and receptors do different things, that is just how it is.
The Pathway of converting external signals into responses with the cell:
- RECEPTION: The ligand activates the receptor
- TRANSDUCTION (Protein Modification): The receptor phosphorylates (gives ATP) the transduction enzymes so it changes into something that can be used.
- RESPONSE: The enzyme then activates a transcription factor, that then creates some mRNA, which creates protein.
Can turn on/off genes, etc.
If a G-protein is used it activates a protein which then activates another protein, which is a secondary messenger in a way.
Steroids go RIGHT THROUGH into the nucleus, whereas proteins need a MEMBRANE RECEPTOR.
Transduction / Phosphorylation cascade:
They use ATP for the enzymes that amplify the protein, so it works better for the response.
Programmed/planed cell death (so it doesn’t become cancer or be taken over by a virus.
Cell Proliferation: cell division