ATP-Dependant Pumps and Ion Exchangers Flashcards
What is the main function of the sodium potassium ATPase?
Essential for making the sodium potassium gradient which allows electrical excitability to drive secondary active transport to…
- control pH
- regulate cell volume
- absorption of Na+ in epithelia
- nutrient uptake from small intestines
What is the problem with high intracellular calcium?
It is toxic to cells
Why are calcium levels kept low intracellularly?
To prevent calcium phosphate forming which will stop ossification occurring in all cells
Why is a low baseline of calcium useful?
It enables us to use very slight rises in calcium to produce cell signals.
Which 3 mechanisms are involved in controlling resting calcium levels?
- Na+ K+ ATPase
- Na+ Ca+ exchanger - this swaps 1 Ca+ out for 3Na+
- works has a low affinity for calcium but a high capacity, this works as it acts when high Ca+ concentration (so affinity can be low) and high capacity allows lots of calcium to be pumped out
- Ca2+ ATPase - this takes the calcium out at lower concentration so has a higher affinity and lower capacity (Ca2+ pumped out and H+ pumped in)
How do calcium ions enter the mitochondria?
If calcium is too high in the cytoplasm, calcium uniporters can transport calcium across the mitochondria membrane due to the electrical potential created by protons being driven out of the mitochondria, as this leaves a negative charge.
What is the SERCA?
Is the sarco endoplasmic reticulum Ca2+ ATPase which can transfer Ca2+ into intracellular stores, to remove them from the cytoplasm.
What happens to the calcium sodium exchanger if the cell becomes depolarised?
It will reverse the direction of the pump (calcium into the cell and sodium out) this is when the charge is positive inside the cell
What happens in ischaemia?
ATP levels are low whcih affects the sodium potassium pump, so the cell becomes less polarised so the calcium sodium pump reverses direction and the calcium enters the cell
(It also affects the Ca2+ ATPase too)
Calcium levels in the cell gets too high which is dangerous
What are the 2 acid extruders?
Sodium - hydrogen exchanger
Sodium bicarbonate cotransporter (sodium dependent Cl-/HCO3- exchanger) - drives protons out and chloride and carbonate ions in
What is the anion exchanger?
(AKA. Cl-/HCO3- exchanger)
Removes carbonate ions out of the cell and chloride ions into the cell, it is a type of ‘base extruder’
What stimulates sodium hydrogen exchanger?
Activated by growth hormones
What inhibits sodium hydrogen exchanger?
Amiloride
What is essential about the combination of mechanisms for preventing cells swelling?
The mechanisms must be electro neutral to prevent a cell becoming excited
