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Homework Help: Biochemistry-Double check my answers please

  1. Oct 10, 2007 #1
    Biochemistry--Double check my answers please

    1. The problem statement, all variables and given/known data

    Part 1: 32 kJ/mol of free energy is needed to synthesize ATP from ADP and Pi when all reactants are at standard conditions (1M). In a human hepatocyte (liver cell), concentrations are far less. Calculate the actual free energy of the synthesis of ATP when concentrations are [ATP]=3.5 mM, [ADP]=1.50mM and [Pi]=5.0mM.

    Part 2: A 150 lb human adult requires ~2000 kcal of caloric intake per day. Assuming that efficiency of metabolism is only 50%, calculate the mass of ATP used by a human adult in 24 hours. Use number obtained in #4 for your calculation. (Note: 1 calorie = 4.184 Joules)

    2. Relevant equations

    delta G= standard G + RT ln (products/reactants)

    3. The attempt at a solution

    For part 1, I did:

    Delta G= 32,000 J/mol + (8.315 J/(mol*K))(298K) ln (ATP/(ADP*Pi))
    Delta G= 32,000 J/mol + (2477.87 J/mol) ln (3.5x10^-3)/(1.5x10^-3 x 5x10^-3)
    Delta G= 32,000 J/mol + (2477.87 J/mol) ln (466.667)
    Delta G= 47228 J/mol

    For part 2, I did:

    [(0.5)*(2000 x 10^3 cal)*(4.184 J)*(503 g/mol ATP)] all divided by 47228 J and got 44561.5 g ATP

    Thanks for your help!
    Last edited: Oct 10, 2007
  2. jcsd
  3. Jan 29, 2017 #2


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    Science Advisor
    Gold Member

    This all looks fine. I want to point out that, yes, in fact your body does use on the order of 40-50 kg of ATP per day, due to the massive amount of recycling that goes on in your cells.
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