Life as we know it?

[Moontanman]

Originally Posted by Donk

You're postulating a single chemical able to do all the things I posted above: defence, offence, digestion/growth, replication. I'm suggesting that a community of specialised chemicals held in place by a cell wall would be able to outcompete the single-chemical forms and would therefore supersede them over time.

No, I'm suggesting a lots of different chemicals doing everything a cell can do but outside a cell in solution. Lots of different metabolisms all doing their own thing as each uses the results of other reactions in it's own reactions. with chemosynthesis and photosynthesis operating in this solution to provide a continuous source of chemicals to feed the other reactions. This is called the metabolism first theory.

What I am suggesting is that there was no reason to expect cells to arise in this sea of chemicals. Cells would have been an oddity with no connection with the initial formation of life. Something must have given these cells some advantage over the free floating chemicals or cells were an accident that may not happen in most or any other planetary life.

The problems connected with cells would have been over whelming until cell walls that could differentiate between the chemicals that needed to come in the cell and chemicals that needed to stay out and chemicals that needed to leave and chemicals that needed to stay. Three maybe four steps away from the life soup and all of them needed to make a cell work.

Either there was some real and obvious reason cells needed to form or cells were an accident. I honestly can't think of a reason cells would be better than the living soup so that leaves accidental formation. I'm betting at the very least it took much longer to form cells than it did to form a living ocean of chemicals.

[Eclogite]

Originally Posted by Moontanman

Either there was some real and obvious reason cells needed to form or cells were an accident.

There may be a real and obvious reason.

NASA scientist Dr Jason Dworkin and his team from the SETI institute were able to create bubbles of material with the appearance of cells. They did this by taking mixtures of ices, with compositions comparable to those thought to be commonplace in interstellar space, and bombarding them with ultra-violet radiation. When immersed in water, droplets +/-10 micro-m with an inner and outer layer formed.

A team of scientists from Oxford, University of Colorado and the National Oceanic and Atmospheric Administration postulated an important role for aerosols. These tiny droplets form as water evaporates from the ocean and may remain suspended in the atmosphere indefinitely. Today there is a significant content of organic material present in such droplets. Some of this material coats the outer surface of the particle. Evaporation increases the concentration of organics, while collision with meteoric dust could provide metallic elements. The droplets are exposed to a variety of temperature and radiation conditions that might promote chemical reactions.
The size, organic coating, and salinity that differs from sea water are all features of the particles shared by the simplest, prokaryote life forms, such as bacteria.

In short, it may be that a cellular structure is a pre-requisite for providing adequate concentrations of pre-biotic chemicals to allow auto-catalytic metabolisms to emerge.

[Note: I've lifted these comments (middle two paragraphs) from a working document of mine on the Drake equation. I think they are my own words paraphrasing the original articles, but they might be condensations from popular accounts at the time.]

[HydrogenBond]

Life as we know it requires water. No enzyme, DNA or RNA can work with any other solvent, nor do any of these work very well in air. Based on these simple observations and basic logic water is essential to life as we know it. The question becomes, what is there about water that gives water special properties needed for life? It has to do with hydrogen bonding, that same variable that is also important to bio-molecules. Simple logic would say maybe there is a connection, with life evolving hydrogen bonding because it is also important to water. This seems like the smartest way to extend the unique properties of water to life.

This connection does not discount the existing mechanisms for life. But what it suggests is these mechanisms are not complete since they leave out a variable which can be shown to be essential to all biological activity. In other words, let us take an enzyme and express its mechanism. Next, we will dehydrate it to see if the enzyme still holds true to that mechanism. Obviously it won't, so this mechanism does not tell the whole story.

Let me give an analogy for biology. We have a child learning to ride a bike with their dad (water). He is helping by holding the bike. What we do is concentrate all our attention on the child and bike, and ignore the dad and try to correlate the ride of the child out of the context of the dad. Even though the child won't even get going without his dad, dad is not important. We will assume somehow the child spontaneously gets going with a certain random magic. It has nothing to due with dad helping to hold up the bike or give a push. That is common wisdom in a nut shell. To move things into the future, we need to do it the hard way and include all the variables. I realize the old way is easier, but the future way is more logical and scientific.

Once we advance the old fashion way, when questions are asked like, life as we know it, the answers will become more modern and less philosophical. Right now the theory opens the door to almost anything because of the all the unknowns, including dad.

[Moontanman]

Originally Posted by Eclogite

There may be a real and obvious reason.

NASA scientist Dr Jason Dworkin and his team from the SETI institute were able to create bubbles of material with the appearance of cells. They did this by taking mixtures of ices, with compositions comparable to those thought to be commonplace in interstellar space, and bombarding them with ultra-violet radiation. When immersed in water, droplets +/-10 micro-m with an inner and outer layer formed.

A team of scientists from Oxford, University of Colorado and the National Oceanic and Atmospheric Administration postulated an important role for aerosols. These tiny droplets form as water evaporates from the ocean and may remain suspended in the atmosphere indefinitely. Today there is a significant content of organic material present in such droplets. Some of this material coats the outer surface of the particle. Evaporation increases the concentration of organics, while collision with meteoric dust could provide metallic elements. The droplets are exposed to a variety of temperature and radiation conditions that might promote chemical reactions.
The size, organic coating, and salinity that differs from sea water are all features of the particles shared by the simplest, prokaryote life forms, such as bacteria.

In short, it may be that a cellular structure is a pre-requisite for providing adequate concentrations of pre-biotic chemicals to allow auto-catalytic metabolisms to emerge.

[Note: I've lifted these comments (middle two paragraphs) from a working document of mine on the Drake equation. I think they are my own words paraphrasing the original articles, but they might be condensations from popular accounts at the time.]

I've read another slightly less complex version of this idea that says that cell like structures form when waves like the surf break on shore and oil and water forms microscopic droplets very similar to the droplets in vinegar and oil salad dressing. They are composed of two layers and contain cell sized bubbles of water and what ever other chemicals was contained in the water. You idea is a bit more detailed and allows for more complexity. I still question how the cell wall that allows in certain chemicals and lets out certain chemicals at the same time could have formed by accident. Of course when you are talking about literally thousands of billions of such "cells" forming and possibly joining all the time it becomes far more likely.

[Eclogite]

Originally Posted by Moontanman

I still question how the cell wall that allows in certain chemicals and lets out certain chemicals at the same time could have formed by accident. Of course when you are talking about literally thousands of billions of such "cells" forming and possibly joining all the time it becomes far more likely.

I think this is the central point that the researchers were making. The proto cell wall is very general in the way it inhibits or admits the passage of material into, or out of the droplet. A chance combination of molecules within that wall may lead to a more useful concentration of chemicals within the droplet. If an autocatalytic reaction involving proto-cell wall molecules and components within the droplet gets underway you could have 'replicating' simple metabolisms.

I don't believe this is the way life began, but I believe it may have been part of the sequence.

[Moontanman]

Originally Posted by Eclogite

I think this is the central point that the researchers were making. The proto cell wall is very general in the way it inhibits or admits the passage of material into, or out of the droplet. A chance combination of molecules within that wall may lead to a more useful concentration of chemicals within the droplet. If an autocatalytic reaction involving proto-cell wall molecules and components within the droplet gets underway you could have 'replicating' simple metabolisms.

I don't believe this is the way life began, but I believe it may have been part of the sequence.

I think it might have been several different functioning but separate metabolisms that came together in proto cells. these proto cells could combine and even divide due to physical processes and eventually enough of these cells were formed that could function as life, possibly with the help of free floating RNA. At each step of combining separate cells with functioning metabolisms better and better cells were formed. there is probably no one time and place where you could point and say, there is a living cell but once the cell got started they would pretty much take over possibly only leaving RNA viruses as the remnants of the time when metabolisms were separated from each other in proto cells.

[mynah]

Update on the "cells" in red rain

They are obviously not cells as we know them, but they do have some pretty weird qualities. I haven't seen any details about their actual composition, however.

[Moontanman]

Originally Posted by mynah

Update on the "cells" in red rain

They are obviously not cells as we know them, but they do have some pretty weird qualities. I haven't seen any details about their actual composition, however.

I've been following the "red cells" story for quite a while and I really don't know what to make of it. The red cells thing doesn't have much support in main stream science. I know the "World Science" has a lot stuff in it's reports that is somewhat less than exactly accurate science. I like to read it but I take most of it with a grain of salt.