Calcium Homeostasis Flashcards
What is the normal extra cellular Ca2+ Concentration and how much is free?
2.5 x 10^-3 M
Free: 1 x 10^-3 M
What is the normal intracellular cytoplasmic Ca2+ concentration
1 x 10^-7 M
What is the main channels for Ca2+ to move from the extra cellular space to the cytoplasm
- Voltage Gated Channels (VGCC)
- Ligand Gated Channels (LGCC)
- Store Operated Channels (SOC)
What are the main channels to move Ca+ into the extra cellular environment
- PMCA ( Plasma Membrane Ca2+ ATPase)
- NCX (Na-Ca2+ Exchange)
Describe how the NCX works
- Uses the Na concentration gradient (Secondary Active transport)
- Moves 3 Na in and Ca2+ out
- Intracellular Na balances with Na/K-ATPase
Describe how the PMCA works
- Uses one molecule of ATP to transport ONE molecule of Ca2+ out
Describe what usually binds to LGCC
Neurotransmitters
What channels move Ca2+ from the SR/SER into the cytoplasm
- IP3 receptors
- Ryanodine Receptors
What process does Ryanodine receptors use to change concentrations of cellular Ca2+
Calcium Induced Calcium Release
How are Ryanodine receptors different in ‘Skeletal muscle’ than in ‘Cardiac and Smooth Muscle’
They are physically coupled with the GPCR
When the GPCR is activated, the Ryanodine receptor opens to
What channel transports Ca2+ from the cytoplasm into the SR/SER
SERCA (Smooth Endoplasmic Reticulum Ca2+ ATPase)
Where are the main stores of Ca2+
- Extracellularly
- Smooth Endoplasmic Reticulum / Sarcoplasmic Reticulum
- Mitochondria
What is the intracellular concentration of Ca2+ in the SER / SR
Up to 1 x 10^-3 M
Where does Calcium bind on proteins
Over exposed oxygen atoms
How can the affinity of PMCA to Ca2+ be further optimised
By binding to Calmodulin
