HBIO 320 EXAM QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS GRADED A++ LATEST UPDATE
Distribution of Ions can create a difference in
Electrical Potential
- measured in Volts (usually mV for physiology)
Electrochemical Gradient
The diffusion gradient of an ion, which is affected by both the concentration difference of
an ion across a membrane (a chemical force) and the ion's tendency to move relative to
the membrane potential (an electrical force).
t • Ions have two gradients • Chemical gradient Maintained by
Na+ /K+ ATPase
Electrical gradient three characteristics
1. Opposites attract; same charges oppose
2. Inside of the cell is negative
3. The stronger gradient will drive ion movement
Potassium gradient
chemical gradient = wants to move out of cell
electrical gradient = wants to move into cell
Sodium, chloride, and calcium concentration
higher outside the cell
Potassium concentration
, higher inside the cell
Equilibrium potential
mV value where the chemical gradient has the same strength as the electrical gradient
equilibrium potential is specific to a
certain ion
e.g. EP for potassium is -90mV •
Example: if cell is -80 mV, then potassium would
leave the cell until the cell becomes -90mV(ish)
Cell's electrical potential would match Potassium's equilibrium potential if
cell is permeable to ONLY Potassium
Membrane Potential
Cell's maintenance electrical disequilibrium (-70)
The ion with the greatest permeability has the
greatest influence on the cell's membrane potential.
Because Potassium is more permeable than the other ions, the cell's membrane
potential will be
closer to Potassium's equilibrium potential.
Cell membrane potential won't be -90 mV, because
the other ions make it more positive
(but because they are not as permeable, it is still closer to - 90 mV than any other ion's
equilibrium potential)
COMPLETE SOLUTIONS GRADED A++ LATEST UPDATE
Distribution of Ions can create a difference in
Electrical Potential
- measured in Volts (usually mV for physiology)
Electrochemical Gradient
The diffusion gradient of an ion, which is affected by both the concentration difference of
an ion across a membrane (a chemical force) and the ion's tendency to move relative to
the membrane potential (an electrical force).
t • Ions have two gradients • Chemical gradient Maintained by
Na+ /K+ ATPase
Electrical gradient three characteristics
1. Opposites attract; same charges oppose
2. Inside of the cell is negative
3. The stronger gradient will drive ion movement
Potassium gradient
chemical gradient = wants to move out of cell
electrical gradient = wants to move into cell
Sodium, chloride, and calcium concentration
higher outside the cell
Potassium concentration
, higher inside the cell
Equilibrium potential
mV value where the chemical gradient has the same strength as the electrical gradient
equilibrium potential is specific to a
certain ion
e.g. EP for potassium is -90mV •
Example: if cell is -80 mV, then potassium would
leave the cell until the cell becomes -90mV(ish)
Cell's electrical potential would match Potassium's equilibrium potential if
cell is permeable to ONLY Potassium
Membrane Potential
Cell's maintenance electrical disequilibrium (-70)
The ion with the greatest permeability has the
greatest influence on the cell's membrane potential.
Because Potassium is more permeable than the other ions, the cell's membrane
potential will be
closer to Potassium's equilibrium potential.
Cell membrane potential won't be -90 mV, because
the other ions make it more positive
(but because they are not as permeable, it is still closer to - 90 mV than any other ion's
equilibrium potential)
