Thread: DNA Ester Bonds?

http://www.youtube.com/watch?v=v8nYTJf62sE

I have been recommending this YouTube video to people, which seems to be pretty well done. But I have been getting questions back, which I couldn't really answer.

I have received some comments about how the hydrogen cyanide and ammonia solution would become oxidized and would not produce adenine. But the response to that is that there was no oxygen in the earth's early atmosphere. - A good video to watch is "How the earth was made" a 2 part History channel documentary.

Question:

In DNA and RNA, where did ester bonds come from? Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. However, according to scientific theory, in the earth's early atmosphere there was no oxygen, so how could phosphodiester bonds have been formed to make up the backbone of DNA, since ester bonds require oxygen? Without these bonds, you couldn't have DNA or RNA.

There was plenty of oxygen around in the early Earth, just not atmospheric oxygen (O2). Most oxygen was bound up in CO2, CO, organic compounds, and mostly in water.

Originally Posted by i_feel_tiredsleepy

There was plenty of oxygen around in the early Earth, just not atmospheric oxygen (O2). Most oxygen was bound up in CO2, CO, organic compounds, and mostly in water.

Okay, got it. It is thought that asteroids blasted the earth and brought in most of the water from space. Then it rained for millions of years. This is estimated 4.4 billion years ago, so there would have been all the water on the earth prior to the emergence of the first single-celled organism 2 billion years ago. The break up of water molecules by UV light would have produced some atmospheric oxygen. So there was oxygen for ester bonds to form.

So then how would you counter the statement that the hydrogen cyanide, ammonia solution becoming oxidized which would not allow adenine to be produced?

Its like if you say there was oxygen, adenine couldn't have been produced. But if you say there was no oxygen, ester bonds could not have been formed. How do you address this?

Originally Posted by juantonwan

Originally Posted by i_feel_tiredsleepy

There was plenty of oxygen around in the early Earth, just not atmospheric oxygen (O2). Most oxygen was bound up in CO2, CO, organic compounds, and mostly in water.

Okay, got it. It is thought that asteroids blasted the earth and brought in most of the water from space. Then it rained for millions of years. This is estimated 4.4 billion years ago, so there would have been all the water on the earth prior to the emergence of the first single-celled organism 2 billion years ago. The break up of water molecules by UV light would have produced some atmospheric oxygen. So there was oxygen for ester bonds to form.

So then how would you counter the statement that the hydrogen cyanide, ammonia solution becoming oxidized which would not allow adenine to be produced?

Its like if you say there was oxygen, adenine couldn't have been produced. But if you say there was no oxygen, ester bonds could not have been formed. How do you address this?

Well I'm no chemist, but from my understanding early Earth conditions would have resulted in any O2 produced to react almost immediately, it's not until the "oxygen catastrophe" caused by photosynthetic organisms that the reduced metals were all oxydized and thus oxygen was able to build up.

The oxygen in organic molecules don't usually come from reaction with atmospheric oxygen, rather they usually come from reaction with CO or CO2. The Urey-Miller experiments suggest that organic acids can be produced, idk if alcohols can be too, but as long as they both exist you can get esterification.

As far as I'm aware, CO and CO2 were included in the experiments that allowed the formation of purines and pyrimidines.