How many atoms in a human cell?

  1. How many atoms could fit inside a human cell?

    "A person's body is actually made up of trillions of cells (source: Science Concepts - Cells by Silverstein)", but how many atoms could fit inside a human cell?

    125 million atoms could fit inside the period at the end of this sentence. But how many atoms could fit inside a single (prokaryote, eukaryote, animal, human, or plant) cell?
    Last edited: Jun 4, 2006
  2. jcsd
  3. Gokul43201

    Gokul43201 11,046
    Staff Emeritus
    Science Advisor
    Gold Member

    A typical human cheek cell has a volume of about 10-13m³. With some assumptions and approximations, I have 1016 atoms, give or take a couple of orders of magnitude.
  4. DaveC426913

    DaveC426913 16,346
    Gold Member

    "125 million atoms could fit inside the period at the end of this sentence."

    This seems conservative in the extreme.
  5. Pengwuino

    Pengwuino 6,949
    Gold Member

    Maybe he meant with room to spare :biggrin:
  6. Gokul43201

    Gokul43201 11,046
    Staff Emeritus
    Science Advisor
    Gold Member

    If you consider the period to be two dimensional, I'd imagine that estimate being conservative by only a couple or so orders of magnitude.
  7. 125 million atoms in the period at the end of this sentence would seem accurate though all you would see off the computer screen would be light. So actually there would be no mass therefore no atoms(excluding the flowing electrons in the computer screen). Otherwise a palpable ink dot would most likely contain 125,000,000 atoms
  8. DaveC426913

    DaveC426913 16,346
    Gold Member

    How do you back this up?
  9. alxm

    alxm 1,845
    Science Advisor

    Re: How many atoms could fit inside a human cell?

    And most of the cells in the human body aren't human. Which is pretty indicative of the vast difference in size between human cells and bacterial ones. And there's a big difference between different human cells.

    E-Coli has 5.44 million base pairs in its DNA. Reckoning ~30 atoms per nucleotide, 125 million atoms wouldn't even cover half the atoms in its DNA.
  10. Andy Resnick

    Andy Resnick 6,087
    Science Advisor
    Education Advisor

    estimating the volume of a cell as 10 cubic microns, and a density 1.3 times that of water, gives 4.5*10^11 atoms/cell.

    A dot of ink, 1 micron thick and 0.5 mm in diameter has a volume of 7*10^5 cubic microns.
  11. Re: How many atoms could fit inside a human cell?

    On November 2, 2009, according to the National Geographic, "Each cell in the human body contains about 100 times as many atoms as there are stars in the Milky Way. As we all know, the Milky Way has ~ 200 Billion stars. SOOooo, 200,000,000,000 X 100 = 2.0 × 1013. Long story short, it's about, 200 trillion. Now, that's magnificent isn't it!

    Hold your horses my little stem cells, Science NetLinks, a resource for science teachers, stated that there are approximately "ten to the 14th power" (that's 100 trillion) cells in the human body. SOOOooo, 200 trillion atoms in 1 human cell X 100 trillion cells in the average human body = a whopping, 200 septillion. That's a 2 with 24 zeros following it! Are you conceptualizing this! We have 100 times more atoms in out body than stars in the universe! [Please see footnote "A"

    Let's not stop there shall we? How about 200 septillion atoms in the average human body X, as of November 2, 2009, the Earth's population is estimated by the United States Census Bureau to be, 6.794 billion = 13.588 X 10 34 ! GULP! I better go make breakfast. (:smile:)

    The One and Only!
    Even if I have 2 Z's in my registration name. Oops...

    Footnote A The total number of stars in the universe is roughly 100 billion x 100 billion.

    That's 10,000,000,000,000,000,000,000 stars, 10 thousand, billion, billion. Properly known as 10 sextillion. And that's a very conservative estimate.
  12. Last edited: Nov 2, 2009
  13. Are there any authoritative sources for how much individual somatic cells mass?

    I've read that there's about ~10 trillion nucleated somatic & white-blood cells in an average adult, about 25 trillion denucleated red blood cells and about 40 trillion bacteria of all stripes.

    As humans - and most animals AFAIK - float, then the average density must be less than water. Most of the molecules in our bodies numbers-, if not mass-, wise are probably good old H2O, then there's the CHON that makes up most of the carbs, lipids and proteins in our bodies... so, elementally, we're probably mostly oxygen. If an average human masses ~75 kg & they're roughly 8/9ths oxygen, then we contain roughly 4200 moles of oxygen. About 2.52E+27 atoms of oxygen - and the 35 trillion human cells contain about 72 trillion oxygen atoms each.
  14. According to this source... Ed Uthman, MD site ...there's 43 kg of oxygen in a 70 kg human. So I should have said ~3/5 oxygen instead of ~8/9. Oh well. You can do all the figuring you like off the neat breakdown presented on the page. I suspected there was more oxygen because we're 70% water to start with and then oxygen is present in sugars/carbohydrates, bone, and other odds and ends. Oh well.
  15. After throwing the data into a spread-sheet it's interesting to see how much hydrogen dominates in terms of numbers of atoms...

    hydrogen 62.2%
    oxygen 24.1%
    carbon 12%
    nitrogen 1.2%
    phosphorus 0.2%
    calcium 0.2%

    ...we're still mostly "star-stuff" especially if you count white-dwarf star-stuff ;-)
  16. DaveC426913

    DaveC426913 16,346
    Gold Member

    True, though not in volume or mass.


  17. Pretty pics Dave! Where'd you find that periodic table template?
  18. DaveC426913

    DaveC426913 16,346
    Gold Member

    Thanks. I don't recall where I got the original PTotE. I just Googled until I found one that suited my purpose.
  19. lisab

    Staff: Mentor

    Awesome, Dave :approve:.
  20. To answer the original question, there's 6.72E+27 atoms in 70 kg of human, of which 2.54E+27 are not hydrogen. Thus in 35 trillion cells there's an average of ~192 trllion atoms per cell, ignoring the bacteria that mostly live in the gut and don't mass too much.
  21. Danger

    Danger 9,663
    Gold Member

    I know that I have at least 6 cells in my brain, because I have binocular vision and can see the 3 main colours with each eye. I assume that there are a couple of others that control my typing fingers. Beyond that, I haven't a clue.
Know someone interested in this topic? Share this thead via email, Google+, Twitter, or Facebook

Have something to add?