Calcium Flashcards
What effect does the big difference in intracellular and extracellular concentrations in calcium have?
It means that very small changes in concentration have large effects inside the cell
Why are there very low calcium levels inside the cell?
High calcium levels are toxic to the cell and result in cell death. It causes ossification of tissue as it calcifies the cells.
What is the extracellular concentration of calcium?
1mM
What are the 6 methods of moving calcium into the intracellular space?
- Store Operated Channels (SOC)
- Voltage Gated Calcium Ion Channels (VGCC)
- Ligand Gated Ion Channels (LGIC)
- Sodium Calcium Exchanger (NCX)
- GPCR in plasma membrane
- Ryanodine Receptors
What are the 3 methods of moving calcium out of the cytosol?
- PMCA
- NCX
- SERCA
How does the sodium calcium exchange work?
The pump utilises the electrochemical gradient set up by the Na/K ATPase which provides a large conc of Na outside the cell. Therefore the cell moves 3 sodium ions in and 1 calcium Ion out. The pump has a low affinity for calcium
How does the Plasma Membrane Calcium ATPase work?
Using one molecule of ATP to transfer one ion of calcium out of the cell. This has a high affinity for calcium and a low capacity
How do Store Operated Channels work?
A sensing protein in the ER detects when calcium levels inside the cell are low and activated the Channels to open.
How do voltage Gated Calcium Channels work?
The Channels open in response to depolarisation
How to ligand Gated Ion Channels work?
Open when ligands bind to them, as they cause a conformational change
How is the NCX able to transport calcium both into and out of the cell?
When the cell is depolarised the Exchanger can change direction to pump calcium in and sodium out to try and counteract the depolarisation as it has a net change in charge as it attempts to repolarise the cell
How does the SERCA work?
Works the same as the PMCA but on the SER/ER membrane. It uses 1 molecule of ATP to transport calcium into the ER from the cytosol.
How do GPCR receptor increase intracellular calcium levels?
Activation of the GPCR by an agonist causes the production of IP3 which binds to the IP3 receptor on the ER membrane (therefore acting as a LGIC) which then open allowing calcium ions to move out.
How do Ryanodine receptors work?
After depolarisation VGCCs open and the calcium ions that move into the cytosol bind to the RyR receptors opening them, allowing the release of calcium ions from the ER (POSITIVE FEEDBACK)
What is the name given to the type of CALCIUM RELEASE by the Ryanodine receptors?
CALCIUM INDUCED CALCIUM RELEASE