F) Catalysis of one mole of ATP molecules yields -30.5kJ of energy. How many ATP
ID: 1376372 • Letter: F
Question
F) Catalysis of one mole of ATP molecules yields -30.5kJ of energy. How many ATP molecules must the Na+/K+ ATPases break down in order to restore the above loss in the electrical energy? Assume all of the energy liberated from the catalysis of ATP is available for work. Excitable cells (such as neurons and muscles) have voltage-gated sodium channels, which open in response to changes in the membrane potential. When these channels open, the membrane resistance to sodium ions drops from 4.5 x 10^8 omega to 3.38 x 10^6 omega . Then, positively charged sodium ions in the extracellular space flow into the cell (because the cell interior is at a lower potential), thereby increasing the potential inside the cell. This sodium influx ceases when the membrane potential finally becomes +58mV, the equilibrium potential for sodium. Therefore, the potential difference that drives sodium current is 125mV (the difference between +58mV and -67mV ). #9 There is a potential difference between the interior and exterior of all animal cells, and this potential difference is called 'resting membrane potential'. It has a magnitude of -67mV (the cytoplasm being electrically negative compared to the extracellular space), and is maintained by the sodium-potassium pump (also called Na+/K+ ATPase), which pumps out three sodium ions and takes in two potassium ions in each cycle, thereby resulting in translocation of one net positive charge out of cell each time.Explanation / Answer
Potential difference V = 125 mV
= 125 x 10 -3 V
Loss in energy E = 30.5 kJ
= 30.5 x 10 3 J
In problem negative sign indicates loss
We know E = ( 1/2) CV 2
= qV / 2 Since q = CV
From this charge q = 2E / V
= 488000 coulomb
Number of ATP molecules N = q / e
Where e = charge of electron
= 1.6 x 10 -19 coulomb
Substitue values you get N = 3.05 x 10 24
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