L4 - Control of Intracellular pH

Question 1

What scale is pH?

Answer 1

Logarithmic - pH = -log10[H+]

Question 2

What are acid extruders?

Answer 2

• Substances that remove H+ from or add HCO-3 to a cell
• The Rate of acid extrusion is Je

Question 3

What are acid loaders?

Answer 3

• Removes HCO-3 from a cell.
• The rate of acid loading is measured JL

Question 4

What are the factors involved in the control of intracellular pH?

Answer 4

• Buffering
• Acid Extrusion
• Acid Loading

Question 5

Buffering

Answer 5

• A pH buffer is any system that moderates the effects of an acid or alkali load, by reversible consuming or releasing protons.
• Work to minimise pH changes to protect the cell from damage.

Question 6

What does buffering by proteins rely on?

Answer 6

The ability of COOH and NH2 groups on amino acids to donate or receive protons.

Question 7

What is the set point of NHE (Na/H exchanger)?

Answer 7

• When the pH is more alkaline than the set point the exchanger is inactive.
• Activity of the exchanger is stimulated at acidic pH.

Question 8

What is allosteric modification?

Answer 8

Protons other than the one being transported bind to the NHE protein leading to conformational change increasing the activity of the proton.

Question 9

NHE1

Answer 9

• Has roles in regulation of intracellular pH and control of cell volume.
• Inhibited by low levels of amiloride and EIPA.
• Found in the basolateral membrane of epithelial cells.

Question 10

AE1

Answer 10

Predominantly found in Red blood cells, there are some in the kidney responsible for the chloride/hamburger shift.