W2 - Cell to Cell Signalling Flashcards
(55 cards)
What is trans autophosphorylation?
The molecule phosphorylates itself and then passes that phosphate on
What happens once a GPCR is activated?
GTP replaces GDP bound to alpha subunit, alpa/beta/gamma heterotrimer dissociates and alpha dissociates from this
Where does the GTP alpha go after it dissociates and what does this do?
Goes to effector protein and activates a cascade to reach target
What are the two forms of direct signalling?
Gap junction signalling and juxtacrine signalling
What are the four indirect forms of signalling?
Autocrine, paracrine, endocrine and neuronal signalling
In what instance would membrane bound receptors be typically used?
When the signal is hydrophilic (except gases)
What happens after transduction if there’s no 2nd messenger or if it’s there but is inactive?
Not there - enzyme is activated to produce 2nd M, is there but inactive - changes conformation of enzyme/messenger to activate 2nd M
Ligand and receptor interactions can be fast and/slow, give examples of these?
Fast - altering protein function (act/deact), Slow - altering gene expression (takes longer due to transc/transl)
What determines what the head and tail is in a fruit fly?
The protein gradients formed by bicoid and nanos proteins
What type of signalling is involved in the formation of chicken limbs?
Paracrine
What does the ZPA do?
Sends out signals which instruct the developing limb bud on how to form along the posterior/anterior axis
What would give more reference points in terms of ‘decisions made’ by what/how much morphogen are present and why?
Having multiple morphogens can give many more combinations to instruct what to produce (e.g. neurons from SC)
How to test French Flag hypothesis
Have normal ZPA working and observe, cut ZPA from one embryo using eyelash and add to opposite side (to current ZPA) of another to alter gradients
Wolpert’s conclusion is…
A morphogen produces a signalling gradient and this gives identities at thresholds
What is on the X and Y axis of Wolpert’s graph?
X - distance from morphogen source, Y - conc of morphogen
What is the difference when writing bicoid mRNA or bicoid protein?
mRNA - lowercase and italics, protein - capital letter and upright
What is special about the specificity of serine + threonine kinases and why?
Either kinase can phosphorylate either aa because their side chains are similar
Why can kinases only phosphorylate serine/threonine/tyrosine?
It requires a polar hydroxyl group on side chain
Why does phosphorylation increase hydrophilicity in serine/threonine/tyrosine?
Adds -ve charge so makes side chain charged
What does phosphorylation of tyr/thr/ser do to the structure of protein, allowing it to alter activity of another protein?
Conformational change
What enzymes are required for dephosphorylation?
Phosphatase enzymes
Are molecules always activated once phosphorylated?
No they can be inactivated too
What is the key steps of amplification?
One activated receptor activates many 2nd messengers, the 2nd messengers activate multiple kinases until they’re removed from cytosol/metabolised, each kinase can activate multiple targets
Amplification can be big or small, is it ever not there?
No
