L3 - Control of intracellular pH Flashcards
What scale is pH measure on
Logarithmic
Decrease in pH means
An increase in acidity
High pH
Low acidity
High alkalinity
Low pH
High acidity
Low alkalinity
pH =
-log[H+]
Why should we worry about a change in pH
Can have profound physiological effects
What compensation must be made when pH increase
Remove H+
Alkalinisation
What compensation must be made when pH decreases
Increase H+
Acidify
How can pH IC be measure
Two electrodes inserted containing a H+ sensitive resin
and difference measures
Graph of pH vs voltage
Linear with a negative gradient
Equation to calculate V
= (slope x pH) + offset
Equation to calculate pH from graph
(V - offset) / slope
How may flourescent indicators be used to measure intracellular pH
Cells loaded with a lipid soluble, inactive form of the indicator
Indicator converted to active form inside of the cell
Indicator is excited with light of a specific wavelength and ammount of light emitted at the second wavelength is measured
FLOURESCENCE IS PROPORTIONAL TO THE INTRACELLULAR PH
Indicator is calibrated inside of the cell
Membrane permeablised with proton ionophore, pH of bath = ph IC
3 factors involved in pH IC regualtion
Buffering
Acid extrusion
Acid loading
What is a pH buffer
Any system which moderates the effect of an acid/alkali load by reversibly consuming or relaseing protons
Buffer systems act to
Minimise pH changes
What is buffering power
The ammount of a strong base that must be added to raise the pH by given ammount
What do buffers NOT prevent
Changes in pH
Merely acts to minimise the magnitude of the change
Can buffers reverse pH changes
No
COOH is a
Proton donor
NH2 (amino group) is a
Proton reciever
What does acid extrusion mean
Getting acid out of a cell
What transport protein is needed for acid extrusion
NHE
Sodium proton exchanger
What does acid extrusion rely on
The inward Na gradient created by the Na/K ATPase
