A nerve cell is shaped like a cylinder. The membrane wall of…
A nerve cell is shaped like a cylinder. The membrane wall of the cylinder has a +0.07-V potential difference from the inside to the outside of the wall. To help maintain this potential difference, sodium ions with a charge of +e are pumped from inside the cell to the outside. For a typical cell, 109 ions are pumped each second. (e=1.602×10-19 C) a. How large is the surface of a nerve cell compared to a sodium ion? Does the cell’s shape matter? (2 marks) b. Determine the change in chemical energy each second required to produce this increase in electric potential energy. (4 marks) c. If there are roughly 7×1011 of these cells in the body, how much chemical energy is used in pumping sodium ions each second? (2 marks) d. Estimate the fraction of a person’s metabolic rate used to pump these ions. Use 100 W as an average metabolic rate. (2 marks)