Another Contribution To Life's Origin Story

[hazelm]

https://www.sciencedaily.com/releases/2018/06/180613101933.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Ftop_news%2Ftop_science+%28ScienceDaily%3A+Top+Science+News%29

 

Polymers form from monomers.  On early Earth this would have been difficult without the help of  the then missing enzymes.   A possible solution?  A simple chemical process.  Large polymers could have formed from alpha hydroxy acids before the presence of enzymes on Earth.

 

 

[exchemist]

https://www.sciencedaily.com/releases/2018/06/180613101933.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+sciencedaily%2Ftop_news%2Ftop_science+%28ScienceDaily%3A+Top+Science+News%29

 

Polymers form from monomers.  On early Earth this would have been difficult without the help of  the then missing enzymes.   A possible solution?  A simple chemical process.  Large polymers could have formed from alpha hydroxy acids before the presence of enzymes on Earth.

Yes polyesters. Esters are very easy to make from alcohols and fatty acids: all you need is a bit of acidity or alkalinity as a catalyst.

 

Making amides from amines and fatty acids is harder. (Normally we make amides by reacting amines with acid chlorides, eliminating HCl, rather than from the acids themselves, by elimination of H2O.) 

 

But this does not go very far. All it shows is that, surprise surprise, you can get a lot of combinations of polyester molecules. But as polyesters today play little role in biochemistry, this does not really seem to help all that much in explaining how polyamides became so important (e.g proteins). 

[hazelm]

Yes polyesters. Esters are very easy to make from alcohols and fatty acids: all you need is a bit of acidity or alkalinity as a catalyst.

 

Making amides from amines and fatty acids is harder. (Normally we make amides by reacting amines with acid chlorides, eliminating HCl, rather than from the acids themselves, by elimination of H2O.) 

 

But this does not go very far. All it shows is that, surprise surprise, you can get a lot of combinations of polyester molecules. But as polyesters today play little role in biochemistry, this does not really seem to help all that much in explaining how polyamides became so important (e.g proteins). 

Are you saying that polyesters are the same as polymers?  Please remind me what HCI stands for.  I know what I thought but  I am obviously wrong.  Thank you.

[exchemist]

Are you saying that polyesters are the same as polymers?  Please remind me what HCI stands for.  I know what I thought but  I am obviously wrong.  Thank you.

A polyester is one type of polymer. HCl is hydrochloric acid. 

 

An ester is an organic compound made by a so-called "condensation" reaction between an organic acid (a.k.a. "carboxylic acid" or "fatty acid") and an alcohol. The acid has a group of atoms like this on the end" -OC-OH and the alcohol has a group like this HO- . An ester is an acid and an alcohol joined by making a link between these two that looks like this -OC-O-, releasing a molecule of water (H2O) in the process. If you count the atoms you will see this.  

 

If you have a "hydroxy acid", you have a molecule with BOTH an HO- and a -OC-OH group on it, which will look like this:

 

HO-R-OC-OH (R stands for a hydrocarbon chain of some kind).

 

You can think of the -OC-OH as a "hook" and the HO- as an "eye. So then you have molecules with a hook on one side and an eye on the other, enabling you to link the hook of one with the eye of the next indefinitely, in a long chain:

.........-O-R-OC-O-R-OC-O-R-OC-O.R-......

 

That is a polyester, because the links in the chain consist of a lot of ester groups: -OC-O-.  

 

In a protein you have something a bit different, involving an acid as before -OC-OH and an amine H2N- i.e with a nitrogen atom and 2 hydrogens, instead of an alcohol with an oxygen atom and one hydrogen.   You can make a similar kind of hook and eye linkage, which looks like this -OC-NH- instead of -OC-O-. A molecule containing this type of link is called an amide. Amino acids, the building block of proteins, have an acid "hook" and an amine "eye". So proteins are polyamides:

 

....-NH-R-OC-NH-R-OC-NH-R-...

 

So this is why polyesters and polyamides could be relevant to compare, in the context we have been talking about. But, as the authors say, making the amide links is harder than making ester links.  

Edited June 16, 2018 by exchemist

[hazelm]

A polyester is one type of polymer. HCl is hydrochloric acid. 

 

An ester is an organic compound made by a so-called "condensation" reaction between an organic acid (a.k.a. "carboxylic acid" or "fatty acid") and an alcohol. The acid has a group of atoms like this on the end" -OC-OH and the alcohol has a group like this HO- . An ester is an acid and an alcohol joined by making a link between these two that looks like this -OC-O-, releasing a molecule of water (H2O) in the process. If you count the atoms you will see this.  

 

If you have a "hydroxy acid", you have a molecule with BOTH an HO- and a -OC-OH group on it, which will look like this. HO-R-OC-OH (R stands for a hydrocarbon chain of some kind). You can think of the -OC-OH as a "hook" and the HO- as an "eye. So then you have molecules with a hook on one side and an eye on the other, enabling you to link the hook of one with the eye of the next indefinitely, in a long chain: .........-O-R-OC-O-R-OC-O-R-OC-O.R-...

 

That is a polyester, because the links in the chain consist of a lot of ester groups: -OC-O-.  

 

In a protein you have something a bit different, involving an acid as before -OC-OH and an amine H2N- i.e with a nitrogen atom and 2 hydrogens, instead of an alcohol with an oxygen atom and one hydrogen.   You can make a similar kind of hook and eye linkage, which looks like this -OC-NH- instead of -OC-O-. A molecule containing this type of link is called an amide. Amino acids, the building block of proteins, have an acid "hook" and an amine "eye". So proteins are polyamides: ....-NH-R-OC-NH-R-OC-NH-R-...

 

So this is why polyesters and polyamides could be relevant to compare, in the context we have been talking about. But, as the authors say, making the amide links is harder than making ester links.  

Thank you, I think.  The vocabulary is different from the article and that takes some thinking.   Give me a few hours.  It really is a fascinating article where they say they've bypassed what was thought to be a barrier to the start of life. 

[exchemist]

Thank you, I think.  The vocabulary is different from the article and that takes some thinking.   Give me a few hours.  It really is a fascinating article where they say they've bypassed what was thought to be a barrier to the start of life. 

Sorry Hazel there may be rather more chemistry in my reply than you wanted. Polyesters are one type of polymer. Polyamides, which is what biological polymers such as proteins are, are another. Both are made from molecules with a molecular "hook" on one side and a molecular "eye" on the other. 

[hazelm]

Sorry Hazel there may be rather more chemistry in my reply than you wanted. Polyesters are one type of polymer. Polyamides, which is what biological polymers such as proteins are, are another. Both are made from molecules with a molecular "hook" on one side and a molecular "eye" on the other. 

No problem at all, exchemist.  There are a number of new (to me) terms which does not mean "I pass" but means "I want to see what these mean".  I didn't get a chance yesterday because I was overwhelmed with other things.  Today is clear and - given the temperature outside - I have plenty of time to get that job done. 

 

I am almost sure those terms will be synonyms (or near so) of the terms in the article.  If I ran into them once here, I'll be running into them again somewhere.  Better plunge in.

[hazelm]

All right.  Am I making sense here?  In your descriptions of polyesters (a polymer form?) and/or proteins, there are no enzymes present?   Or is what you posted additional information to flesh out the story and when polymers can form and when they can not?

 

I had another question but I cannot, for the life of me, find where you posted what I remember.  Maybe later.

 

Thanks much.

[exchemist]

All right.  Am I making sense here?  In your descriptions of polyesters (a polymer form?) and/or proteins, there are no enzymes present?   Or is what you posted additional information to flesh out the story and when polymers can form and when they can not?

 

I had another question but I cannot, for the life of me, find where you posted what I remember.  Maybe later.

 

Thanks much.

Yes. The formation of polyesters can be done without an enzyme, using just simple inorganic acids or bases as the catalyst. 

 

The formation of amide links from amino acids, however, can't be catalysed this way. You need an enzyme. (In the organic chemistry lab we make amides another way, but that requires first of all converting the fatty acid group to something else, using very strong reagents which would wreck the machinery of a living or proto-living cell. So that route is a non-starter as a natural process.) 

 

The extra information I posted is about what the links are that join molecules together in a polyester and in a polyamide (protein).  

[hazelm]

Yes. The formation of polyesters can be done without an enzyme, using just simple inorganic acids or bases as the catalyst. 

 

The formation of amide links from amino acids, however, can't be catalysed this way. You need an enzyme. (In the organic chemistry lab we make amides another way, but that requires first of all converting the fatty acid group to something else, using very strong reagents which would wreck the machinery of a living or proto-living cell. So that route is a non-starter as a natural process.) 

 

The extra information I posted is about what the links are that join molecules together in a polyester and in a polyamide (protein).  

Ah, that's what I wanted - where/when enzymes are called for.  Thanks.  One of these days one of these hypotheses is going to prove correct and matters will be settled -- until someone comes up with a better idea.  Or at least a new argument pro/con.   We humans are good at that, too.  Yes?