Control Of Intracellular PH Flashcards
What is important to note about blood and intracellular pH?
They are different
Intracellular pH is the pH in the cell. This may DIFFER to the pH in the blood
What is the equation for pH?
PH = -log10 [h+]
How do proteins act as buffers for pH changes inside of the cell? What is an important feature of proteins in cells?
Proteins inside of cells have charged residues. I.e. charged carboxyl and amino groups
When there is a pH change, proteins inside of the cell act as buffers. They buffer the pH. This causes their charges to change.
How does a change in the charge of a protein affect its function?
Other proteins can’t bind to the proteins which have had their charges altered. Their functions have also altered.
What if there is a small change in pH? What happens to protein concentration inside of the cell?
There is a large increase in protein concentration to buffer the change.
What do bronchial proteins inside of the cell do?
They regulate pH
They specifically respond to an alkaline shift.
Once activated their charge is changed - the charge reflects that of an acid and helps make the cell a little more acidic in the presence of the alkaline
How does temperature affect proton concentration (H+) and thus pH of the INSIDE of the cell?
An increase in temperature causes the concentration of protons in the cell to increase, thus alkalinity goes down
A decrease in temperature in the cell causes transporters to be activated which remove excess protons from the cell - causing alkalisation.
How do you measure the pH of the cell?
This is basically the same principles you use for testing the intracellular voltage of the cell with microelectrodes
However in this instance
One microelectrode has a tip sensitive to protons and another electrode this is linked to is normal
You the measure the potential of the cell in comparison to the normal electrode. This tells you the pH
To calibrate the electrode (proton tip one) put the in solutions of pH standards 6 and 8 and measure the voltage each time. Then plot this on a graph.
What is significant about the tip on the microelectrode of the proton sensitive one?
The tip is quite large and thus may damage small cells. Better to use on bigger cells.
How to measure pH from a graph you plotted with taking measurements from the intracellular pH of the cell and the the pH of a pH 6 and 8 solution?
PH = voltage offset / slope of the graph
2nd type of technique (so doesnt use microelectrodes) to tell you the intracellular pH?
PH indicators which are made fluorescent. This gives off green light when a light is shone on it, telling you pH. The indicator is thus excited and is charged when a specific wavelength of light hits it.
What is the issue with using a fluorescent indicator to measure pH?
Its hard to get an ACTIVE fluorescent indicator into the cell
Once you get the ACTIVE flourescent indicator into the cell its hard to get it back out (this is the active form)
How do you get the fluorescent indicator into the cell?
Get the indicator into the cell in the inactive form. This form is lipid soluble
You then have lateral enzymes which cleave the indicator to give you an active form. This form gets trapped inside of the cell.
The level of fluorescence shown by the indicator tells you PH
What is flourscence of a pH indicator equivalent to?
Intracellular pH
How do we find out the precise pH using a fluorescent indicator?
We expose the cell to a proton ionophore. This makes the membrane permeable to protons. PH of the cell becomes the same inside and outside. You then measure fluorescence.
