Re: How many atoms are in a cell?

Dear Paul,

Thanks for your question. 
I hope my explanation is clear enough for you to understand it.

You probably know all living organisms are made of cells. Some cells are 
complete organisms, such as bacteria and others, such as muscle cells, are 
specialized components of multicelular organisms.

Cells vary greately in their composition and size. For example: the 
smallest bacteria is about 0.1 micrometres in diameter (thatīs 
the 10,000,000 of a meter) and egg yolks of ostriches are about 8 cm (0.08 m) 
in diameter (really big, donīt you think!?)Although cells might differ 
widely in size, appearence and functions, they are all composed primarily 
by 4 different types of atoms: Oxygen, Hydrogen, Carbon and Nitrogen.  
These four elements make up the majority of organic compounds. The most 
important organic compounds in a cell are: 

1.Proteins

They are very large molecules, ranging in molecular weight from a few 
thousand to more than a million, and they are specific for each species and 
for each organ of each species. Humans have an estimated 30,000 different 
proteins. 

Proteins are composed of units of about 20 different amino acids, which, in 
turn, are composed of carbon, hydrogen, oxygen, nitrogen, and often 
sulfur. In a protein molecule these amino acids form peptide bonds. The 
almost numberless combinations in which the acids line up, and the helical 
and globular shapes into which the strands coil, help to explain the great 
diversity of tasks that proteins perform in living matter.


2.Nucleic Acids

Nucleic acids have at least two functions: to pass on hereditary 
characteristics from one generation to the next, and to trigger the 
manufacture of specific proteins. All living cells contain the genetic 
materials DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). One cell 
has about one meter of DNA. The complete set of genes in each of your cells 
is 3 billon base pairs. (thatīs about 150 billon atoms)

3.Lipids (oil)

Lipids are distinguished from other classes of organic compounds in that 
they do not dissolve in water but are soluble in organic solvents.
Among the most important lipids are the phospholipids, which are major 
components of the cell membrane. (1 single fatty acid is made of 
aproximately 50 atoms)

4.Polysaccharides (sugar)

Compounds in the carbohydrate group that are readily soluble in water; are 
colorless, odorless, and usually crystallizable; and are more or less sweet 
in taste.


Water makes up to 60-65% of an average cell, because itīs a favourable 
environment for biochemical reactions.


Well, as you can see, cells are quite complex tiny structures. You canīt 
possibly know the exact number of atoms in a cell but letīs say you can 
find as many atoms in a cell as stars in the sky...:)

Hope my answer will help.

Just in case you want to know more about cells:

http://library.advanced.org/3564/
http://www.mblab.gla.ac.uk/dictionary/
or if you have Microsoftīs Encarta Encyclopedia 98-99 you can look for the 
information given under cell.

Talia Arcari
State University
Montevideo
Uruguay