The K+ concentration inside a nerve cell is found to be 20x higher outside the cell...

The K+ concentration inside a nerve cell is found to be 20x higher outside the cell than inside the cell, while the Na+ concentration is 20x higher inside versus outside. A. If the membrane potential Em (Ein-Eout) is -77.6 mV, identify the ion that must be transported actively versus the ion that is near equilibrium (assuming ideal conditions). B. The NA+ -K+ -ATPase (or sodium-potassium pump), moves three sodium ions from inside to outside, and two potassium ions from outside to inside while simultaneously hydrolyzing ATP to ADP + Pi. If ATP/ADP is 40 and [Pi] is 25mM, estimate the change in potential (∆µ kJ/mol) for the sodium transport, potassium transport and ATP to ADP + Pi separately (assuming ideal conditions). C. A researcher proposes that perhaps a single ATP hydrolysis is sufficient for two rounds of Na+ /K+ exchange (i.e., move 6 Na+ atoms out and 4 K+ atoms in). Is the hydrolysis of a single ATP sufficient to account for the active transport of ions for a single cycle? For two? Assume ideal conditions & Justify your answer. D. Now imagine we are in non-ideal conditions, and the ionic strength on the inside of the cell is much higher than outside the cell. Considering only the sodium export, will this export be more or less favored when compared to the ideal scenario (Justify your answer)

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Expert Solution

Answer-

A. The concentration of sodium ion is more in extracellular side i.e outer isde of cell membrane . So while Na+ enter into i.e from out side to inside cell it does not need any ATP

In similar way, if K+ passes out from the cell it goes from higher to lower concentration.

B. When Na+ need to move out and K+ ion need to move in against the concentration gradient, it needs ATP/ energy . So sodium-potassium pump helps in moving sodium ions out ans potassium ions in.

The potential difference becomes - 70mV to 40mV and comes back to the normal stage soon after the passing of ions.i.e cell membane stay in resting state at- 70mV potential outside.

C. Na+ - K+ pump or sodium potassium ATPase enzyme is a solute pump that pumps sodium out of cells while pumping potassium into cells, both against their concentration gradients. This pumping is active (i.e. it uses energy from ATP) for moving Na+ to outside the cell and K+ to inside the cell.

The process of moving sodium and potassium ions across the cell membrance is an active transport process involving the hydrolysis of ATP to provide the necessary energy. It involves an enzyme referred to as Na⁺/K⁺-ATPase.

For every adenosine triphosphate molecule i.e ATP molecule that the pump uses, three sodium ions are exported, while two potassium are imported; there is hence a net export of a single positive charge per pump cycle.

D. If higher concentration of ionic strength will be more inside the cell that outside the cells . The cell will not mainin its equilibrium and nerve cell can not maintain the resting potential.

Hence action potential or nerve transmission will not happen .

gladiator answered 1 year ago

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