# Number of atoms in a cell

1. May 20, 2004

### mee

I know there are trillions of cells in an adult human body but how many atoms are in each cell?

2. May 20, 2004

### Monique

Staff Emeritus
Very crude: What does the average adult weigh, devide by the number of cells. What are the most common atoms in a cell and what are their relative abundancies, what do they weigh on average. Divide the weight of a cell by the average weight of the atoms represented in a cell.. and there you get your number :)

Maybe someone already figured it out and you can find it on Google :)

3. May 21, 2004

### arildno

Even cruder, but it should be an upper bound on the number of atoms in a cell:
Let V be the average volume of a cell.
Then we should have the inequality for the number n atoms in a cell:
$$n\leq\frac{V}{\frac{4}{3}\pi{R}^{3}}$$

Where R is an average value for an atomic radius

4. May 21, 2004

### Monique

Staff Emeritus
But how much space is taken up by the 3D structure of a molecule, and how much space is there between molecules..

5. May 21, 2004

### arildno

That's why it's such an awfully crude upper bound