Cell Signalling Flashcards
Why do cells communicate?
Essential for survival:
-blood glucose
-infection
-wounding
-time to contract
-time to divide
-time to die
What are ligands
Signalling molecules-> hormones, neurotransmitters, cytokines, chemokines etc
5 different types of cell signalling:
- direct signalling
- paarcrine signalling
- endocrine signalling
- synaptic signalling
- autocrine signalling
What is direct signalling?
Cells can share molecules between each other
(Plasma membrane- gap junctions)
What is paracrine signalling?
Signalling molecule is released by a cell to an adjacent cell (immune system cell, eg. Vascular endothelial growth factor)
What is endocrine signalling?
Gland secretes hormone directly into the blood, travels through the blood to an organ further away, target organ responds to stimuli (testosterone)
What is synaptic signalling?
Nerve cell releases a neurotransmitter, acetylcholine travels across synaptic gap and binds to receptors
What is autocrine signalling?
Cell will release a hormone/signal, and binds to receptors on itself. Immune cell releases cytokines- binds to receptors on itself as well as surrounding cells. Leads to changes within the cell itself
What are the four receptor classes that a signal binds to:
- steroid receptor
- G-protein coupled receptor
- Ligand-gated ion channels
- Enzyme linked
What are the responses to cell signalling?
Change protein production
Change protein activity
What does changing protein production do?
Switch genes on and off
What does changing protein activity do?
Turn enzymes on and off
Reorganise the cytoskeleton
Outline steroids (testosterone)
-all come from cholesterol
-steroid binds to enhancer regions within the DNA
-made up of carbon rings
-hydrophobic
-lyophilic (can pass through cell membrane)
Outline steroid receptors:
- when steroids bind to steroid receptors-> localised to the nucleus
- steroid receptors act as transcription factors-> move to nucleus-> turn on genes-> bind to enhancer region on DNA-> promotes formation of RNA polymerase complex-> production of mRNA
- leads to synthesis of proteins
Outline G-protein coupled receptors:
-found in cell membrane
-1 in 20 human genes code for a GPCR/ 800-1000 receptors
-40% of pharmaceuticals bind to GPCRS
-serpentine receptors-> span the membrane 7 times
-heterotrimeric-> 3 different subunits
Outline what adrenergic is
Contrasting effects on different receptors depending on the tissue - coupled with GTP- binding proteins
Beta receptors on the heart
Alpha one receptors found in the gut + sympathetic target tissues
Alpha two receptors mainly on the digestive organs
Outline kinases role:
-kinases add phosphate to macromolecules
-phosphorylase specific amino acids within the protein- serine,threonine
-change activity of target proteins and lead to an effect in the cell
- tyrosine phosphotases are a subset of serine/threonine protein phosphotases
How signals are turned off
cAMP gets broke down by enzyme called phosphodiesterase into AMP
Inhibit phosphodiesterase by enzyme PD3, switch processes off
Outline ligand gated ion channels
Ligands bind to their receptor that has a pore/channel, when activated ions rush in.
All cells have a resting membrane potential due to ions travelling through pores through this membrane
In a gradient potential how many sodium ad potassium ions are pumped in and out
3 sodium out
2 potassium in
Outline enzyme linked receptors
Receptors signal for kinase cascades- enzymes that phosphorylase macromolecule, altered activity in the protein, add a phosphate group onto a transcription factor -> synthesis of a new protein
