How many molecules are in the human body?
Here's what I get.
Scientists recently made the most precise estimate so far of the number of cells in the human body — a whopping
They then used tabulated values and some other tricks to arrive at a value of roughly 27 pg for the average mass of a cell.
About 65 % of a cell's mass is water.
Thus, an average cell contains about 18 pg of water and 9 pg of other substances.
With some judicious guesses as to the average molar masses, we can calculate the number of molecules in the cell ("we leave that as an exercise for the student …").
Note: The "other" substances in the cell are ionic substances, not molecules.
This is the number of molecules in a cell.
The number of molecules in the body is
Thus, the body consists of about
Warning! Long Answer. It depends on mass of the body. However, the body of a 57 kg teenager would consist of about
Here's a second answer. It shows how the numbers you get depend on the assumptions you make.
The body of a newborn infant will have fewer molecules than that of an overweight adult.
Let's assume that you are a teenager with a mass of 57 kg.
Scientists estimate that your body is
- 61 % water
- 16 % fat
- 16 % protein
- 6% minerals
- 1% carbohydrate
Minerals include inorganic ions such as sodium, potassium, chloride, hydrogen carbonate, and phosphate.
Thus, your body consists of
#"water"color(white)(mmmm) "34.8 kg"# #"fat"color(white)(mmmmmm) "9.12 kg"# #"protein"color(white)(mmmll) "9.12 kg"# #"minerals"color(white)(mmml) 3.4color(white)(ll) "kg"# #"carbohydrate"color(white)(ll) "0.57 kg"#
With some judicious guesses as to the average molar masses, we can calculate the number of molecules.
Minerals are not molecules, so I will omit them from the calculation
Let's assume that the average molecular masses are
#"water:"color(white)(mmmmmmm) "18.02 u"# #"fat":color(white)(mmmmmmmml)1000 color(white)(l)"u"# #"protein:"color(white)(mmmmmll)"30 000 u"# #"carbohydrate:"color(white)(m)"1 000 000 u"#
Thus, the total number of molecules in your body is
So, your body consists of