Biophysics

Question 1

What is the membrane potential

Answer 1

The difference between the electrical potential in the cytoplasm and the electrical potential in the extracellular space.

Question 2

How is the membrane potential measured

Answer 2

An intracellular electrode is used to measure the transmembrane potential with respect to the electrical potential of the extracellular solution

Question 3

What is the extracellular concentration of K, Na, Ca, Cl and HCO3 respectively

Answer 3

4.5, 145, 1.0, 116,24

Question 4

What is the intracellular concentration of K, Na, Ca, Cl and HCO3 respectively

Answer 4

120, 15, 0.0001, 20, 15

Question 5

Is the Na K pump electronegic and what does this mean

Answer 5

Yes, displacement of charge generates an electrical current

Question 6

What 3 channel types are associated with maintaining the resting Vm

Answer 6

Na/KATPase - Loss of positive charge, contributes 20% of -70mV
K channels - 80% of resting Vm - Movement of K out removes positive charge from inside the cell creating a potential difference across the membrane
Na channels - Cell at rest has low permeability to Na - however influx of Na into the cell leads to repulsion of other Na ions - K channels are leaky and let a few Na ions through