Control of Intracellular pH Flashcards
What is the scale of pH
logarithmic
What is the normal range of pH inside cells
7 - 7.1
What can buffer pH changes
proteins, acid extrusion, acid loading
How do proteins buffer pH changes
Accept and donate protons from their charged residues
True or False - protons and pH are important primary messengers in cells
False - they are secondary messengers
What is the effect of increasing proton concentration on pH
pH becomes more acidic - decreases
How do cells compensate for an acidic pH
remove excess protons
What two methods can measure intracellular pH
microelectrodes and fluorescent indicators
Describe the two microelectrodes
V1 has a proton sensitive resin tip, V2 is normal
What does V2 measure
total membrane potential
What does V1 measure
membrane potential of everything except protons
What is a disadvantage of using electrodes to measure pH
They are large so may damage small cells
How do fluorescence indicators measure pH
pH inside the cell will be proportional to the fluorescence intensity
Describe the inactive form of pH indicators
lipid soluble so passes through the cell membrane
What is an ionophore bath used for
to make the pH inside the cell the same as the pH outside the cell.
What is the effect of protein ionophore on the membrane
makes the membrane freely permeable to protons
Which approach to measure pH is best for small cells
Fluorescence indicators and ionophore bath
What is a limit of buffering
Cant reverse pH change
Definition of buffering
amount of strong base that must be added to a solution in order to raise the pH by a given amount
Which protein group increases pH
NH2
how does NH2 increase pH
receives protons
Which protein group decreases pH
COOH
What is the function of the COOH group in regard to pH
Release H+ to decrease pH
What is an example of an acid extrusion protein
Na/H exchanger
Describe the movements by the sodium hydrogen exchanger
moves sodium in and protons out
What type of transporter is the NHE
secondary active transporter
What does NHE rely on
gradient set up by the sodium potassium ATPase
When does the sodium proton exchanger become active
under acidic pH conditions
What is allosteric modification
more than one proton binds to the NHE exchanger
What is the effect of allosteric modification on the NHE
increases activity of protein by a conformational change
What are the functions of NHE
pH regulation and control of cell volume
What inhibits NHE
low concentrations of amiloride
Where is NHE found
basolateral membrane of epithelial cells
What is the function of the C terminus in NHE
major regulation site
What is the effect of calcium carmodulin on NHE
Causes an alkali shift in the set point
Name an acid loading exchanger
Cl/HCO3 exchanger (AE)
Describe the transport of the AE
moves bicarbonate out and chloride in
What is the effect of bicarbonate moving out of the cell by the AE on pH
free protons left inside the cell decrease pH
When is the Cl/HCO3 exchanger activated
alkaline pH
What inhibits the AE family
stillbene drugs
Which transporter is independant of sodium
Cl- HCO3 exchanger
When does the resting intracellular pH occur
during NO NET movement of protons
