lab midterm #2

Question 1

You measure the membrane potential of a cell and find that it is -60mV. What does this mean?

Answer 1

This means that the inside of the cell is 60 millivolts more negative than the outside.

Question 2

Ion X has an equilibrium potential of -94mV. Use one or two sentences to explain what this really means.

Answer 2

Ion X’s equilibrium potential of -94 mV indicates that there is no movement across the membrane, since the 2 driving forces (chemical and electrical) are balanced.

Question 3

If the concentration of sodium in the extracellular fluid increased, then the equilibrium potential would (become more positive / become less positive / remain the same)?

Answer 3

If the concentration of sodium increased, it would become more positive

Question 4

Assuming that for Na+ (higher concentration outside cell) , ENa+ = +60 mV and VM is -70 mV, what is the direction of the electrochemical gradient?

Answer 4

The electrochemical gradient would move into the cell

Question 5

Anion Q has an equilibrium potential of -60 mV. Q is located in greater concentration (inside / outside) the cell. When a cell is at rest (-70 mV), the direction of the electrochemical force acting on Q is to move it (into / out of) the cell? If channels for Q suddenly opened, the membrane potential would become (more negative / less negative / or not change)?

Answer 5

Q has a greater concentration inside the cell. The electrochemical force will therefore move Q out of the cell and if the channels opened the membrane potential would become less negative.

Question 6

If a negatively charged ion is more concentrated outside the cell, the forces required to balance the chemical gradient would be directed ________. Thus, the equilibrium potential for this ion would be ________ charged.
a) outward : positively
b) outward : negatively
c) outward : neutrally
d) inward : negatively
e) inward : positively

Answer 6

outward, positively

Question 7

An anion is found in greater concentration inside the cell than outside. Which of the following statements best describes forces acting on the anion at the resting membrane potential (-70 mV)?
a) Both the chemical and electrical forces are directed out of the cell.
b) The chemical force is directed out of the cell and the electrical force is directed into the cell.
c) Both the chemical and electrical forces are directed into the cell.
d) There is insufficient information to answer this question.
e) The chemical force is directed into the cell and the electrical force is directed out of the cell.

Answer 7

the chemical force is directed out of the cell and the electrical force is directed into the cell