Cell signalling – signalling modes and signal transduction pathways
BiologyCell BiologyAges 15–16
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Sign in to playCompare direct contact, paracrine and endocrine signalling and quorum sensing in bacteria: drag a target cell nearer or further away to see the ligand concentration fall with distance and the response change, and remove its receptors to see it ignore the signal. On the pathway screen, adrenaline binds a G-protein-coupled receptor that activates adenylyl cyclase, cAMP and a protein kinase cascade; insulin binds a receptor tyrosine kinase; a steroid hormone binds an intracellular receptor that acts as a transcription factor; acetylcholine opens a ligand-gated ion channel. Vary the ligand dose, mutate the receptor or block a step with a drug or cholera toxin, and read the amplification factor and the response.
Lesson: Cell communication: signalling modes, reception, transduction and response, signal amplification
What it shows
Cells communicate with chemical signals (ligands) that bind specific receptors. Signals can pass by direct contact between touching cells, diffuse a short distance to nearby cells (paracrine), or travel in the blood to the whole body (endocrine); bacteria detect their own density by quorum sensing. A response needs reception, transduction and response. Hydrophilic ligands bind cell-surface receptors such as G-protein-coupled receptors, receptor tyrosine kinases and ligand-gated ion channels; steroid hormones cross the membrane and bind intracellular receptors that act as transcription factors. Cascades of second messengers and protein kinases amplify the signal enormously.
How to use
On Signalling modes, pick Direct contact, Paracrine, Endocrine or Quorum sensing, drag the target cell, change Signal release rate and untick Target cell has receptors. On Transduction pathway, choose a pathway, move Ligand concentration, pick a Drug / mutation, and press Wash out ligand or Add ligand to watch the signal switch off and on.
Parameters you can change
- Starting screen Signalling modes, Signal transduction pathway
- Signalling mode Direct contact, Paracrine, Endocrine, Quorum sensing in bacteria
- Signal release rate 10–100 %
- Target cell has receptors
- Bacterial density (log₁₀ cells per mL) 5–11
- Pathway Adrenaline – G-protein-coupled receptor, Insulin – receptor tyrosine kinase, Steroid hormone – intracellular receptor, Acetylcholine – ligand-gated ion channel
- Ligand dose (log₁₀ of concentration) -3–2
- Drug or mutation None, Mutant receptor (cannot bind), Receptor blocker (antagonist), Cholera toxin (G protein stays on), Caffeine (phosphodiesterase inhibitor), Protein kinase inhibitor
Questions to explore
- Why does adrenaline reach every cell in the body but only change the activity of some of them?
- How can one adrenaline molecule lead to the release of millions of glucose molecules from a liver cell?
- Why does cholera toxin cause a response even when no adrenaline is present?
