Liloandstitch24
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We got given this maths questions in a biology question and the explanation the teacher gave didn’t make much sense so I was wondering if anyone could help explain how it is worked out ‘the hydrolysis of 1 dm3 of a 1moldm-3 solution releases 30500j of energy. 60% of the energy released during the hydrolysis of 1moldm-3 of ATP is released as heat; the rest is used for muscle contraction. The student added 0.05cm3 of ATP solution to slide D (conc of ATP solution on slide D is 8x10-6 Moldm-3). Calculate the energy available from ATP for contraction of muscle on this slide.’
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macpatgh-Sheldon
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(Original post by Liloandstitch24)
We got given this maths questions in a biology question and the explanation the teacher gave didn’t make much sense so I was wondering if anyone could help explain how it is worked out ‘the hydrolysis of 1 dm3 of a 1moldm-3 solution releases 30500j of energy. 60% of the energy released during the hydrolysis of 1moldm-3 of ATP is released as heat; the rest is used for muscle contraction. The student added 0.05cm3 of ATP solution to slide D (conc of ATP solution on slide D is 8x10-6 Moldm-3). Calculate the energy available from ATP for contraction of muscle on this slide.’
"‘the hydrolysis of 1 dm3 of a 1moldm-3 solution releases 30500j of energy...…………." Assuming this solution (in bold) is a solution containing ATP, then let us go step by step, OK?

30500 joules of energy corresponds to one mole of ATP (there is one mole of ATP in 1 dm3 of a 1M (1 Molar) solution of ATP (info given).

So how much is 40% (not lost as heat) of this? Of course, 30500 X 0.4 = 12200 joules is given by one mole of ATP, yeah?

OK next step:-
They tell you that 0.05 cm3 of soln was used - so how much ATP in it?
Yes do it bit by bit...…………… well done! 0.05 cm3 = 0.05/1000 dm3 = 5 X 10-5 dm3
Conc-n given = 8 X 10-6 M
So, actual MOLES of ATP in it = (8 X 10-6) X (5 X 10-5) = 40 X 10-11 = 4 X 10-10 moles

Last step:
FROM italics above,
one mole of ATP gives 12200 joules of energy
So how much will underlined amount give?

YES: 4 X 10-10 X 12200 = 12.2 X 4 X 10-7 = 48.8 X 10-7 joules = 4.88 X 10-6 joules (ANSWER).

Hope this is correct!

M (specialist biology tutor)
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User148
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(Original post by macpatgh-Sheldon)
"‘the hydrolysis of 1 dm3 of a 1moldm-3 solution releases 30500j of energy...…………." Assuming this solution (in bold) is a solution containing ATP, then let us go step by step, OK?

30500 joules of energy corresponds to one mole of ATP (there is one mole of ATP in 1 dm3 of a 1M (1 Molar) solution of ATP (info given).

So how much is 40% (not lost as heat) of this? Of course, 30500 X 0.4 = 12200 joules is given by one mole of ATP, yeah?

OK next step:-
They tell you that 0.05 cm3 of soln was used - so how much ATP in it?
Yes do it bit by bit...…………… well done! 0.05 cm3 = 0.05/1000 dm3 = 5 X 10-5 dm3
Conc-n given = 8 X 10-6 M
So, actual MOLES of ATP in it = (8 X 10-6) X (5 X 10-5) = 40 X 10-11 = 4 X 10-10 moles

Last step:
FROM italics above,
one mole of ATP gives 12200 joules of energy
So how much will underlined amount give?

YES: 4 X 10-10 X 12200 = 12.2 X 4 X 10-7 = 48.8 X 10-7 joules = 4.88 X 10-6 joules (ANSWER).

Hope this is correct!

M (specialist biology tutor)
Thanks for the answer! There was a bit I was confused on though...

Why do you times (8x10-6) with (5x10-5)? Is there a particular formula to find moles that you used? Does this mean the amount of ATP that occupies the volume? I just wanted to understand the logic behind it!
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Dr. NotYet
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(Original post by User148)
Thanks for the answer! There was a bit I was confused on though...

Why do you times (8x10-6) with (5x10-5)? Is there a particular formula to find moles that you used? Does this mean the amount of ATP that occupies the volume? I just wanted to understand the logic behind it!
conc x vol = mol as

conc is in mol/dm3 and vol is dm3 which cancel to give mol
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User148
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h

(Original post by Dr. NotYet)
conc x vol = mol as

conc is in mol/dm3 and vol is dm3 which cancel to give mol
thank you!
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