Control of intracellular pH Flashcards
How do you measure pH using electrodes
Two electrodes are used
Electrode 1 is a normal microelectrode measuring Vm
Electrode 2 has a small amount of proline - a H+ sensitive resin in the tip
This measures the Vm for everything apart from proton movement
1-2 gives the change in voltage due to protons which is = to the change in pH
Calibration of electrodes using pH standards
y = mx + c
y = Voltage, X = pH
How do you measure pH using fluorescent indicators
Cell is loaded with an inactive form of a charged molecule
Naturally occurring enzymes cleave the inactive form
Indicator excited with specific wavelength of light and the amount of light emitted at a second wavelength is measured
Fluorescence is pH dependant
Define a buffer
A system that modulates the effects of acid or alkali load by reversibly consuming or releasing protons
What channel is involved in acid loading and how does it work
Cl-/HCO3- exchanger
Inward movement of chloride ions and the removal of bicarbonate from inside the cell - this leaves behind a proton inside the cell causing acidification
What chemical inhibits AE1
DIDS
What channel is involved in acid extrusion
Na/H exchanger - Relies on the function of Na/KATPase to create a concentration gradient for Na to move into the cell.
What is allosteric modification present in NHE1
Protons other than the one being transported bind to the channel at an allosteric site and produce a conformational change in the channel making it more active than before
How do CaM and PKC modulate NHE1
They change the set point of the channel making the exchanger more active at more alkali levels
They bind on the long C-terminus
How many transmembrane domains does NHE1 have
12
What is a role of NHE1
Found on the basolateral membrane of epithelial cells - linked to cell vol control
When is resting pH achieved
When the rate of acid extrusion is equal to that of acid loading
