Receptors & Signalling 2.0 Flashcards
How are enzyme linked receptors activated?
By ligand binding
What is an RTK?
Group of enzyme linked receptors/ single pass transmembrane proteins - Receptor Tyrosine Kinase
What is the function of RTK’s?
important in mitogen signalling process which induces cell division
How is the signalling cascade of RTK’s triggered?
initiated by ligand induced dimerization of the RTK’s- the receptors then auto phosphorylate each other using the tyrosine kinase domain
Once the signalling cascade of RTK’s is triggered, where is the signal transferred to and what is the purpose of these?
transferred to docking sites- docking sites allow proteins that contain a phosphotyrosine binding domain to bind and act as scaffold for larger proteins to join (promotes signal inside of cell)
How are RTK signals turned off?
HINT- RAS
RAS protein contains intrinsic GTPase activity leading to autonomic deactivation
What are some other ways that RTK signalling can be turned off apart from RAS?
- calcium pumped rapidly out of cell
- receptor mediated endocytosis decreases the amount of ligand and receptors
What is Mitogenesis and what is the difference in the Mitogenesis of Unicellular vs Multicellular organisms?
Propagation of living cells
In unicellular organisms- each new division produces an additional organism
In multicellular- many cycles required to make a new individual
Which part of the Mitogenesis cycle does the cell replicate DNA?
S phase
i) The interval between Mitosis and S Phase is…
ii) The interval between end of DNA synthesis and Mitosis is…
What happens in both?
i) G1- cell monitors its environment & size
ii) G2- safety gap ensuring DNA replication is complete before Mitosis
How can we measure the cell cycle position?
By DNA Content using Flow Cytometry!
How does Flow Cytometry work?
- measures DNA content per cell in a dividing cell population through fluorescence
Low fluorescence but high cell count= G1 Phase
Intermediate number of cells but high fluorescence= G2 phase
What are the three checkpoints in the Cell Cycle and what do they check for?
Late G1- before replication, is cell big enough? is environment favourable?
Before M Phase- is all DNA replicated?
Exit of M Phase- are all chromosomes aligned on spindle?
What happens if conditions are too poor for organisms to replicate?
Unicellular- form spores which survive and enter vegetative growth when conditions improve
Multicellular- persists in G1 phase (known as G0)
What proteins control Mitogenesis? How? (3)
Anti-oncogenes (tumour suppressors)
Proto oncogenes- signal transduction
P53- type of anti-oncogene that stops cell cycle at checkpoints to allow time for repair & can also trigger apoptosis to unrepairable cells
