Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 6

Ion Gradients and ATP Synthesis. The ion gradients maintained across the plasma membranes of most cells play a significant role in cellular energetics. Ion gradients are often either generated by the hydrolysis of ATP or used to make ATP by the phosphorylation of ADP.
(a)Cite an example in which ATP is used to generate and maintain an ion gradient. What is another way that an ion gradient can be generated and maintained
(b)Cite an example in which an ion gradient is used to make ATP. What is another use for ion gradients
(c)Assume that the sodium ion concentration is 12 mM inside a cell and 145 m M outside the cell and that the membrane potential is -90 mV. Can a cell use ATP hydrolysis to drive the outward transport of sodium ions on a 2:1 basis (two sodium ions transported per ATP hydrolyzed)if the ATP/ADP ratio is 5:1, the inorganic phosphate concentration is 50 rnM, and the temperature is 37°C What about on a 3:1 basis Explain your answers.
(d)Assume that a bacterial cell maintains a proton gradient across its plasma membrane such that the pH inside the cell is 8.0 when the outside pH is 7.0. Can the cell use the proton gradient to drive ATP synthesis on a 1:1 basis (one ATP synthesized per proton transported)if the membrane potential is +180 mV, the temperature is 25°C, and the ATP, ADP, and inorganic phosphate concentrations are as in part c What about on a 1:2 basis Explain your answers.