pH And Cell Volume Control

Question 1

Normal (extracellular) pH range

Answer 1

7.35 to 7.45
Human tissue survival limits are 6.8 to 7.8

Question 2

What bonds does a change in pH NOT disrupt?

Answer 2

Covalent bonds.
However, does affect electrostatic interactions and H bonds - so alters protein structure and function as well as altering the binding of substrates and ligands

Question 3

What is the normal cytoplasmic pH?

Answer 3

Normally 7.2, but varies widely across other organelles

Question 4

What are the primary buffer systems for pH?

Answer 4

Bicarbonate buffer system
Phosphate buffer system
Proteins - contain numerous H+ binding sites

Question 5

Describe the NA+/H+ exchanger

Answer 5

Exchanges extracellular NA+ for intracellular H+
Electroneutral 1:1 exchange.
Regulates intracellular pH
Regulates cell volume
Activated by growth factors
Inhibited by amiloride
Antiport

Question 6

What does the NBC do?

Answer 6

Alkalinises cell

Question 7

What does the anion exchanger do?

Answer 7

Acidifies cell

Question 8

How does the activity of the Na+/H+ transporter change with pH?

Answer 8

Activity increased as intracellular pH decreases.
The opposite is true for Cl/HCO3- exchange

Question 9

Give some examples of molecules that influence the movement of water into and out of cells?

Answer 9

Ions - e.g. Na+, Cl-, K+
Organic osmolytes (amino acids)

Question 10

What is efflux?

Answer 10

Movement out
Efflux and influx of ions drive the action of transporters