Calcium Flashcards
How much calcium does the body contain and where is it most likely to be found?
The body contains over a kilogram of calcium and more than 99% of it is found in the bones of the skeleton.
What is the blood serum level of calcium?
2mM (8-10mg/dL) of which over 50% is free calcium
How is whole body calcium homeostasis regulated?
Intestinal Ca2+ uptake,
Ca2+ reabsorbtion in the kidneys
Bone calcium regulations
How are these processes regulated?
They are under endocrine control:
You have Ca2+ receptors in the parathyroid gland.
Parathyroid hormone (increased blood calcium)
1,25 dihydroxyvitamin D3
Calcitonin (decrease level of calcium, opposing effect if parathyroid)
What is the concentration of Calcium
Extracellularly?
In the cytoplasm?
In the ER/SER?
Extracellular: 1-2 x 10-3
Cytoplasmic: 1 x 10-7
ER/SER: 2-3 x 10-4
What are changes in intracellular calcium responsible for?
Muscle contraction Neurotransmission / stimulus-secretion coupling Fertilisation Cell death (apoptosis / necrosis) Regulation of metabolism Learning and memory Gene Transcription
How are Calcium concentration gradients set up and maintained?
The plasma membrane is relatively impermeable to Calcium so it doesn’t go in or out unless directed to.
Pumps and transporters that move Ca out of the cytoplasm (see a different card for different types and explanation)
Calcium buffer proteins (calcium binding proteins). These regulate the amount of free calcium in the cytosol.
What mechanisms move Calcium out of the cytoplasm?
PMCA- Plasma Membrane Calcium ATPase. Which moves calcium across the plasma membrane and out of the cell.
SERA- Sarcoplasmic Endoplasmic Reticulum Calcium ATPase. Which moves calcium into the endoplasmic / sarcoplasmic reticulum.
NCX- Sodium Calcium Exchanger. This moves calcium out of the cell while sodium moves in.
What mechanisms increase the concentration of calcium?
Calcium moves across the plasma membrane via:
Voltage gated Calcium channels
Ligand Gated Ion channels (neurotransmitters activated)
Calcium induced calcium release (CICR) = ryanodine receptors. These channels are regulated by calcium and allow the calcium to move from ER/SR to cytoplasm.
Inositol 1,4,5-triphosphate. Receptor (IP3R). These are naturally occurring, ligand gated ion channels that allow Calcium to move out of ER/SR.
What do changed in the calcium concentration of a cell look like?
Changes in Calcium do not jut go up and down. It is also regarding the frequency and amplitude modifications (how quickly the levels if calcium change and how much by). It is also about where in the cell these changes occur.
Changes in Calcium concentration are usually 2-10 fold over basal but changes in micro domains can be much greater.
Complex patters in the change of calcium concentration can be seen including oscillatory, and peak#plateau responses. In addition, these changes in concentration might be restricted and not uniform across the cell.
