Theoretical Biology

[TheJames]

Theoretical could a biological (even synthetic) organism have only the elements Carbon, Nitrogen, hydrogen and oxygen.

 

Could the organism arrange the atoms in such a way so it could take over the role of other elements (sorry if that made little sense)

Like Diamonds carbon conducts electricity but because the four bonds on the carbon atoms are taken Diamonds do not.

 

Could replacements for NADH , ATP , DNA be made?

[zule]

If I am not mistaken, NADH, ATP and DNA have only Carbon, Nitrogen, Hydrogen, oxygen and Phosphorus.

 

Anyway, although we also included phosphorus, I do not think I can imagine a life with only those elements. I think you would need other elements, at this moment I think of sulfur for the structure of the proteins.

[Moontanman]

You might be able to substitute other elements for some of the ones that are now used, here on Earth arsenic is used to make arsenic-sugars by some life forms, replacing phosphorus. I doubt you can get away without at some trace elements along with C N O H

 

http://en.wikipedia.org/wiki/Hypothetical_types_of_biochemistry

 

Arsenic, which is chemically similar to phosphorus, while poisonous for most Earth life, is incorporated into the biochemistry of some organisms.[5] Some marine algae incorporate arsenic into complex organic molecules such as arsenosugars and arsenobetaines. Fungi and bacteria can produce volatile methylated arsenic compounds. Arsenate reduction and arsenite oxidation have been observed in microbes (Chrysiogenes arsenatis).[6] Additionally, some prokaryotes can use arsenate as a terminal electron acceptor during anaerobic growth and some can utilize arsenite as an electron donor to generate energy. It has been speculated that the earliest life on Earth may have used arsenic in place of phosphorus in the backbone of its DNA.[7]

[TheJames]

What about making molecules out of carbon oxygen e.t.c. which mimic the other elements like how carbon can be Graphite Dimonds e.t.c.

[pioneer]

I don't think arrangements of C,H,O,N can mimic other atoms, in any useful practical way. Each atom has a nucleus and is also composed of layers of electron orbitals, with the outer most orbitals the one's connected to that atom's chemistry. Although one might be able to simulate the outer most electrons of another atom, the impact of all the layers below, would be hard to simulate, since C,N,O,H don't have most of these bottom layers.

 

In the figure below C for example has 1S, 2S and 2p, with only the 1S buried below. If took an atom that had 5S at the top it may have 4F, 4D, 4P, 4S, 3D,3P 3S, 2P,2S, 1S all hidden below

 

 

For example, the chemistry of Sodium and Potassium are both based on outer S-orbitals. Both forms ions, with the same charge; Na+ and K+. But because K (potassium) has more bottom layers, than Na (sodium) the cell is able to tell the difference, and will pump out the sodium and bring in the potassium. The hidden stuff makes a difference and would be complicated to simulate. It is easier to just use the atoms, as is.

[Mr Skeptic]

Theoretical could a biological (even synthetic) organism have only the elements Carbon, Nitrogen, hydrogen and oxygen.

 

I think so... but it would be quite hard. We do use various ions which would be much harder to make with only these. Such an organism couldn't evolve since said ions are readily available in the environment (and would probably be poisonous if they weren't used). We also use sulfur for cross-linking, since it can have more than 4 bonds.

 

Osmotic balance would also be much harder.

 

Could replacements for NADH , ATP , DNA be made?

 

I don't see why not... it would be much harder though.