CELL HOMEOSTASIS Flashcards
(20 cards)
Under normal conditions what is the approximate [EC] sodium ions?
145mM
Under normal conditions what is the approximate [IC] sodium ions?
15mM
Why is it important to keep a large gradient of sodium ions between the EC and IC compartment?
A large electrochecmical gradient allows fast action potential to develop and higher conductivity.
What is a key transporter that keeps sodium homeostasis?
Sodium/Potassium ATPase
How does the Na/K ATPase work?
Extrudes 3 sodium ions and takes in 2 potassium ions coupled by the hydrolysis of ATP.
2
How can the rate of transport of the ATPase be affected ?
[Na]
[K]
[ATP]
What can inhibit the the Na/K ATPase?
Cardiac glycosides such as ouabain and digoxin.
What is the order of hierarchy in terms of concentrations?
Mole
Millimole
Micromole
Nanomole
Under normal conditions, what is the [EC] Calcium ions?
1mM (1000000nM)
Under normal conditions, what is the [IC] Calcium ions?
0.0001mM (100nM)
What is the concentration difference between the outside and the inside of the cell in terms of calcium ions?
10,000 fold difference
What are the two mechansims of calcium control?
Na/Ca exchanger
Ca ATPase
How does the Na/Ca function?
The exchanger exchanges extracellular Na ions for Ca ions in a ration of 3 to 1 respectively.
How is is possible to keep the intracellular concentration of calcium ions so low when there is only a 10 fold concentration difference in sodium ions?
By transporting 3 sodium ions at a time, the sodium gradient is effectively cubed.
What family does the Na/Ca exchanger fall into?
SLC8 gene family, a part of the CaCA family. In mammals, 3 forms exist: NCX1-3
What are the Ca ATPases?
Cells contain three types of Ca ATPases:
PMCA - plasma membrane
SERCA - endoplasmic reticulum
SPCA - golgi apparatus
Calcium is an important second messenger. What are the plasma membrane pathways used in calcium signalling for influx into the cytoplasm?
- Voltage operated calcium channels (VOCC)
- Receptor operated calcium channels (ROCC)
- Mechanically activated calcium channels (MACC)
- Store operated calcium channels (SOCC)
What are examples of SOCC?
- IP3 receptors - channels activated by IP3 binding
2. Ryanodine receptors - low concentrations of ryanodine activate the channels and higher concentrations inhibit.
Caffeine and cADP ribose are examples of activators of what receptors?
Ryanodine
What is STIM1
A calcium binding protein that forms a physical link between depleted calcium stores and plasma membrane calcium channels to physically open the channel and refill the stores.
