MadSci Network: Cell Biology

Re: How is it that we know 10 million ATP molecules are formed per second?

Date: Tue May 30 12:20:56 2000
Posted By: Sarah Tegen, Grad student, Molecular and Cell Biology, UC-Berkeley
Area of science: Cell Biology
ID: 959042163.Cb

Hi John,
Your question about how much ATP we make each day is an interesting one!  
Here's what I've found out.  An adult woman needs to burn about 1600 kcal of 
fuel each day, and our body's fuel is ATP.  Each mole of ATP releases about 
8 kcal of energy and we can assume that we MAKE just enough ATP to get by in 
a day.  (Let me quickly try to describe what a mole is.  A mole of molecules 
is the number of molecules it takes to convert from atomic mass units to 
grams.  For instance, the weight of one molecule of water is 18 amu, but if 
you have 6.02 x 10^23 molecules of water, it would weigh 18 grams.  So 6.02 
x 10^23 molecules of anything converts the weight from amus to grams.  If 
this doesn't make sense, you'll learn about it in chemistry).  

So, doing the math we get:  1600 kcal/day/8 kcal/mol=  200 mol ATP/day.  
Then we can convert from moles of ATP per day to molecules of ATP/second.

200 mol/day/86400 sec/day= 2.3 x 10^-3 mol ATP /sec

Then converting from moles to molecules:

2.3 x 10^-3 mol/sec x 6.02 x 10^23 molecules/mol= 1.4 x 10^21 molecules/sec.

This is a lot bigger than the number that you gave me.  But I think the math 
is correct.  The references I used are: Biochemistry by Voet and Voet 
copyright 1990. p. 554.  There is also an article in Scientific American 
about this.  Scienctific American 238(3) p.104-123 (1978)

Admin note: With approximately 10^14 cells in the human body, the rate would come 
to about 10^7 (10 million) ATP molecules/sec per cell.

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