Intreacellular signalling Flashcards
What happens when a hormone acts on a cell?
It initiates signalling events to trigger the nucleus to change the gene expression, e.g. muscle contraction
Where can signalling occur?
Internal or external
What are signalling processes facilitated by?
Protein kinases and protein phosphates, and secondary messengers acting after hormones
Protein kinase
Enzymes that can either attach or remove a phosphate to and from another protein
Where are these phosphates acquired?
ATP
Protein kinase + ATP =
Phosphorylated protein
Protein phosphotase
Removes phosphate from protein
What does phosphorylation do to a protein?
Switches a protein on or off by changing the structure of the polypeptide backbone
What can adding a phosphate to a protein also do?
Turns their charge negative, thus attracting other amino acids
- can make them more or less active
What does the phosphate replace in amino acids?
The -OH group
Serine/threonine kinase
Most protein kinases (A, B, C)
Tyrosine kinase
Growth factor and oncogenes
Explain the effect of hormones on phosphorylation.
- The hormones bind to the receptors and phosphorylate each other
- Receptors then make attract other proteins and become a docking site for other proteins = cascade of interactions
- this signals the cell but is very slow (can take minutes but last for hours)
How do Protein kinase cascades occur?
Mitogen-activated protein kinase (MAPK) used as an example.
Phosphorylation occurs through mitosis.
1. MAPK is doubly phosphorylated - it gets phosphorylated AND phosphorylates other proteins
2. MAPKinase switches on by acquiring 2 phosphates by MAPKinase kinase.
3. This process occurs twice, therefore a cascade
Why do protein kinase cascades occur?
Amplification
