MadSci Network: Biochemistry

Re: How many kilocalories are present in one gram of a mouse?

Date: Mon Mar 22 21:33:00 1999
Posted By: Chris Larson, Post-doc/Fellow Laboratory of Genetics
Area of science: Biochemistry
ID: 920839153.Bc

	Sorry about the delay on this one.  I think what you are asking about 
here is the reverse of the enthalpy of formation of one gram of a mouse, or 
roughly the amount of heat released by the conversion of all the compounds 
in one gram of a mouse into their corresponding free elements in their most 
stable states.  I will admit right now that their is no way I am going to 
calculate this out for you!  However, I can show you the steps to an 
approximation, and you could extend that to the actual calculation if you 
	You are right that most mammalian bodies are seventy percent water by 
weight.  If we assume that the remaining thirty percent is composed of 
various hydrocarbon compounds, then we could approximate those hydrocarbons 
as methane (since that's the best one in the table that I have in front of 
me!).  The molar enthalpy of formation of water is -285 kJ/mole, and the 
molar enthalpy of formation of gaseous methane (sorry, another 
approximation) is -75 kJ/mole.  The minus sign means that heat is released 
upon their formation.  Now you just have to figure out how many moles of 
water and hydrocarbon/methane there are in one gram of a mouse and 
calculate how much heat would be released or consumed by their formation, 
and the reverse of that is how many kJ there are in one gram of a mouse 
(approximately).  Of course, you have to convert from joules to calories, 

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