Cell Homeostasis Flashcards
What are the normal intracellular and extracellular conditions for sodium
high extracellular, low intracellular
What is the function of the thick ascending limb in the loop of Henle
reabsorption of Na+ and Cl-
What are the properties of the apical membrane of the thick ascending limb
impermeable to water, ammonia and protons
What does the reabsorption of NaCl across the TAL create
trans-epithelial osmotic gradient
What is the trans-epithelial osmotic gradient responsible for
counter current multiplication
Activity of what transporter depends on the inward Na gradient
NKCC
What happens if intracellular sodium levels rise
diuresis, increased sodium and chloride in the urine
Describe the normal chemical and electrical gradient for sodium movement
very large for sodium to move into the cell
What problems occur if the sodium chemical and electrical gradient are reduced
action potential propagation problems, slower action potentials
What controls intracellular Na+
Na/K ATPase pump
What does Na/K ATPase require for its action
ATP phosphorylation
What happens to the Na/K ATPase when 3 sodiums bind
phosphorylation
What does phosphorylation of the Na/K ATPase pump trigger
conformational change
What is the effect of this conformational change on the Na/K ATPase
shifts the binding domain from intracellular to extracellular side - moving Na+ out
What does the function of the sodium potassium ATPase pump depend on
ATP, intracellular sodium and extracellular potassium
What is the Na/K+ ATPase inhibited by
cardiac glycolysis, ouabain and digoxin
What is the net effect on the membrane potential of the Na/K ATPase
makes inside of the cell more negative
What does accumulation of K inside the cell create
driving force for potassium to leave the cell - making the cell more negative
What are the normal intracellular and extracellular conditions for calcium
high extracellular calcium, low intracellular calcium
Why is calcium regulation important
calcium is an important second messenger
How does the cell maintain low intracellular calcium
Na/Ca exchanger, Ca ATPase
What does the Na/Ca exchanger transport
exchanges extracellular sodium for intracellular calcium
True or False - the Na/Ca exchanger is electrogenic
True
What is the SLC8
solute co transporter type 8
How many transmembrane spanning domains does the SLC8 have
10
What is the Na/Ca exchanger a member of
SLC8 gene family
How does the SLC8 gene family allow different functions in different cell types
changing its splice variant
What family is the Ca ATPase a member of
P-Type ATPase family
How many types of ATPases are there
2
What are PMCAs
plasma membrane calcium pumps
What is the function of PMCAs
pump Ca2+ across the plasma membrane out of the cell
What is the function of SERCA
pump Ca2+ out of cytoplasm into organelles
What is SERCA
calcium pumps found on sacroplasmic or ER membranes
What are SPCA
Ca2+ pumps on golgi apparatus
How does calcium signalling move calcium
across PM into cytoplasm, or out of storage organelle into cytoplasm
Where are voltage operated Ca chanels found (VOCC)
excitable cells
What are VOCCs activated by
depolarisation
Where are receptor operated Ca channels (ROCC) found
secretory cells and nerve terminals
What are ROCCs activated by
binding of agonist
Example of a ROCC
NMDA receptor
Where are mechanically activated Ca channels found
many cells
What do mechanically activated Ca channels respond to
cell deformation
What is an example of mechanically activated Ca channels
stretch activated channels
What activates store operated calcium channels
depletion of calcium stores
What are the two classes of calcium channels in store membranes
IP3 receptors, ryanodine receptors
What receptors involved in calcium signalling are associated with excitable cells
ryanodine
Which receptor involved in calcium signalling is biphasic
ryanodine
What happens to the SOCCs when IP3 is formed
open and calcium moves out into the cytoplasm
How are the calcium levels restored
SOCCs open and allow calcium to move in and refill the store
Name another protein involved with calcium movement
Stim and Orai channels