Week 2 - Membrane Potentials

Question 1

If you measured the difference in electrical charge between your left and right hands this would be known as?

Answer 1

A potential difference

Question 2

If you measured the difference in electrical charge between the inside and outside of an epithelial cell this would be known as?

Answer 2

A membrane potential

Question 3

If the leads of a voltmeter were connected to the opposite ends of a small battery and read 0.025 volts, how many millivolts (mV) would this be?

Answer 3

25mV

Question 4

Sodium is an example of which of the following?

monovalent cation

divalent cation

monovalent anion

divalent cation

monovalent prion

Answer 4

A monovalent cation

Question 5

With reference to the diagram opposite, if the blue ion channel opened, making the membrane selectively permeable to X-, which of the following statements would be TRUE?

1. Anions would enter the cell.
2. Cations would leave the cell.
3. The membrane potential would become more negative.

Answer 5

None of these statements is TRUE.

Question 6

With reference to the diagram opposite, if the blue ion channel was selectively permeable to Cl- the equilibrium potential for Cl- would be?

Answer 6

-46.6 mV (using the Nernst Equation)

Question 7

What is meant by the term potential difference, what are its units and how you would measure it?

Answer 7

Potential difference is the difference in the amount of energy that charge carriers have between two points in a circuit. **Measured in Volts: or millivolts in physiology

Question 8

What is a membrane potential and how would you measure it?

Answer 8

the difference in electrical charge between the inside and the outside of the neuron. This is measured using two electrodes. A reference electrode is placed in the extracellular solution. The recording electrode is inserted into the cell body of the neuron

Question 9

The difference between anions and cations and the terms monovalent and divalent?

Answer 9

monovalent elements can remove or gain one electron in order to become stable, whereas divalent elements can remove or gain two electrons in order to become stable.

Question 10

How the membrane potential can be modified by movement of ions across the membrane.

Answer 10

if the membrane is selectively permeable to potassium, these positively charged ions can diffuse down the concentration gradient to the outside of the cell, leaving behind uncompensated negative charges. This separation of charges is what causes the membrane potential

Question 11

T/F: If a membrane is selectively permeable to one ion, the magnitude of the membrane potential is directly proportional to the concentration gradient of the ion across the membrane.

Answer 11

True

Question 12

What is meant by the term equilibrium potential?

Answer 12

The electrical potential difference across the cell membrane that exactly balances the concentration gradient for an ion

Question 13

What is the Nernst Equation and how it can be used?

Answer 13

The Nernst equation relates the effective concentrations ( activities ) of the components of a cell reaction to the standard cell potential

Used to determine equilibrium potential of the ICF of a cell