Cell signalling Flashcards
How many cells are in our bodies?
100 trillion cells
How are the first messengers produced and released?
They are produced in one cell and released by diffusion or exocytosis
How are these first messengers detected in target cells?
They are detected in target cell by surface or intracellular receptors
What binds to receptors that triggers a cellular response?
Ligands are signalling molecules that bind to receptors, triggering a cellular response
What properties make a biochemical signal useful and effective? (5)
- Unique enough to relay a defined signal and to only be detected by correct receptors
- Most signal molecules have no biochemical function (except to bind to a receptor)
- Usually, small enough to trave easily
- Synthesised, altered, or released quickly so that signalling can be switched on rapidly (ON)
- Degraded or re-sequestered quickly to cease signalling (OFF)
First messengers are given different names depending on the signalling process involved. What are the names for the first messengers in endocrine and paracrine signalling?
- Hormones in endocrine (long distance) signalling
- Local mediators in paracrine (short-distance) signalling
Same signal can induce different responses in different target cells. Give me one example of this
Adrenaline is produced in the adrenal gland and can travel to either the heart cell or liver cell to increase heart rate or breakdown liver glycogen
Give me 3 hormones that uses endocrine signalling
Adrenaline (epinephrine)
Insulin
Testosterone/ oestrogen
Give me 2 local mediators that uses paracrine signalling
Histamine and Acetylcholine
What is specificity?
Recognition of specific target ligand
What is affinity?
Binding strength
Biochemical signals are detected by what different classes of receptors?
- Ligand gated ion channels
- Enzymic receptors
-G-protein coupled receptors
What are the main features of ligand gated ion channels?
- Multi- subunit, transmembrane protein forming a pore through which specific ions can pass
- Frequently present at neuronal synapses, rapidly responding to neurotransmitter ligands
What are protein kinases?
Protein kinases are enzymes that add phosphate groups to other molecules to activate or deactivate target molecule
What does ligand binding lead to?
Receptor dimerisation
What does RTK stand for?
Receptor tyrosine kinase (RTK)
What do adapter proteins do?
They recognise and bind phosphorylated tyrosine residues
What does the Ras GTPase switch do?
It can switch a GTP bound active or inactive
Ras-GTP activates specific kinases which lead to cell proliferation
Ras is an important__?
Ras is an important oncogene
What is PLC?
Phospholipase C
What does Phospholipase C do?
-Generates 2nd messenger IP3
- IP3 binds to ion channel receptors on endoplasmic reticulum and releases calcium
- Increased calcium ion concentration activates downstream events
Give me 3 features of G-protein-coupled receptors
- 7 Transmembrane domain structure
- Activated GPCR interacts with a heterotrimeric G protein, leading to dissociation of G-protein subunits
- Release G protein subunits to activate various intracellular signalling pathways
What do many GPCRs do?
They activate cAMP production
What can the activation of GPCR lead to?
It may lead to adenylate cyclase activation and cAMP production
What do cAMP do?
It activates particular protein kinases
What do second messengers do?
They generate responses within a cell (e.g. cAMP, IP3)
What does receptor activation generally regulate?
- Cellular metabolism
- Transcription of specific genes in nucleus
- Cell differentiation / division
- Changes in the cytoskeleton
