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Wize University Biology Textbook > Energy & Metabolism

ATP Energy and the Proton Motive Force (PMF)

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ATP and the Proton Motive Force (PMF)

Adenosine TriPhosphate is an energy storage molecule. It stores potential energy (PE) between the negative charges of the phosphate groups.
Photo by OpenStax College / CC BY

Wize Tip
Keeping those negatively charged phosphates next to one another is like keeping three people who really hate each other locked in a small closet.


ATP hydrolysis releases free energy (negative ΔG).
ATP(aq)+H2O(l)→ADP(aq)+Pi(aq)ATP_{(aq)}+H2O_{(l)}\rightarrow ADP_{(aq)}+Pi_{(aq)}


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How Does the Cell Create ATP?

  • ATP is not the only way cells store energy. Another way is by generating an electrochemical gradient. Example: During cellular respiration in our cells, electron energy is used to pump H+ across the plasma membrane to generate an electrochemical gradient called the proton motive force (PMF).
  • The PMF can then be used to synthesize ATP.


The amount of energy stored across a membrane can be calculated using the formula:
ΔG=RTln([x]final/[x]initial)\varDelta G = RT ln ([x]_{final} / [x]_{initial})

R = gas constant (8.314 J/mol K)
T = temperature in K
[x]initial[x]_{initial}= molar concentration of X on the outside of the membrane
[x]final[x]_{final}= molar concentration of X on the inside of the membrane

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Example: ATP Synthesis

Sketch and estimate the Gibbs free energy required to create an ATP molecule from ADP.

If breaking down ATP releases 52 kJ/mol of energy, we have that creating a molecule of ATP from the same materials (ADP and Pi) will require that amount of energy.

See video solution for sketch of Gibbs free energy graph.

Practice: ATP Energy

Which of the following is true?
Extra Practice
High Energy Intermediates (Similar to 2018 question 3)
In high energy intermediates, how is energy stored?
Which of the following is/are false about ATP synthesis?
The large number of ATPs produced in the mitochondria are
ATP Stynthase
Which is TRUE about ATP synthase?
The inner membrane of the mitochondria is filled with cristae (folded parts). How would this aid in increasing ATP production? Explain the structure-function relationship of the inner mitochondrial membrane.
Wize Concept Check
Describe the driving forces of ATPase function. Include as many energetically favorable examples as you can.
Explain how we know ATP hydrolysis can do mechanical work. Use numbers in your answer.
Give a real-life example of an ATP coupled reaction. Write out the equations.
ATP synthesis: Similar to 2014 Question 15
Which statement is FALSE about ATP synthesis?
Which Statement is FALSE about ATP synthesis?
ATP Synthase
Explain the rotor like mechanism of ATP synthase. Use drawings to show the formation of ATP and explain how many H+ are needed to synthesize one ATP molecule.
High Energy Intermediates (Similar to 2018 question 3)
In high energy intermediates, how is energy stored?
ETC question
Oxidative phosphorylation comprises of both the ETC and
chemiosmosis
If you were to measure respiration in isolated mitochondria, which of the following additions would result in the highest proton motive force?
Why is ATP hydrolysis exergonic?
Which of the following statements is correct?
Which of the following is not an energy source for active transport?
How can energy coupling with ATP be described?
Which of the following is not a reason ATP hydrolysis is exergonic?
Which of the following is not a component of the ATP molecule?
Which of the following is not a reason Pi and ADP are more stable than ATP ?
Why are ADP + inorganic phosphate (Pi) more stable than ATP?