Scientists see life as a hugely complex chemical system, typically capable of self-replication (reproduction) and using catalysts (ingredients in a reaction that make it happen faster). They understand that this complexity – i.e. ordered structure – requires some kind of stability, or it would collapse.
The traditional school of thought is that life achieves thermodynamic stability by giving off energy. The idea is that a chemical system is more stable the less energy it has, because more energy means that the molecules will be vibrating and moving around more. We are all familiar with what happens to ice – an orderly, crystalline susbtance – when it is given energy and melts in to water, where the molecules can flow around, mostly sticking together. If more energy is added, the water molecules start to evaporate and convert into a gas – molecules floating around freely with no attachment to one another, i.e. in complete disarray. We can make skulptures of ice and snow, but as soon as they melt, that orderly structure is destroyed and it falls apart.
Imagine building a house where the wall bricks are vibrating at will...
It is thought that life forms strive for thermodynamic stability (i.e. lowest energy state) by giving away energy to their environment. As chemical reaction occur continuously in a cell, energy must also be expelled continuously. And in order to be able to give away energy forever, there needs to be some way of taking in energy that can be given away. (Indeed, I suppose that if no energy is taken in, the cell could perhaps achieve stability, but it would not be able to grow, repair eventual damage, or anything like that... it would not be much alive, I guess...)
However, these reviews suggest a different form of stability, which they call dynamic kinetic stability. It is based on the principle of chemical reactions going both ways – i.e. being reversible – which naturally makes chemical systems unstable, unless there is something preventing the reaction from going either way, so that only one direction is favoured. I will soon explain what a reversible reaction is, but I want you to understand that that is the very thing dynamic kinetic stability avoids. If the reaction can be controlled in a way that makes it go in one way only, then the products are less likely to disintegrate at will, which could cause the entire system to collapse.
My chemistry is rather rusty, and I have never been very good at it in the first place, but hopefully I can explain the basics well enough!
Most chemical reactions are reversible in theory. For example, consider mixing sodium chloride (NaCl) with magnesium hydroxide (Mg(OH)2): they could separate into their constituent ions (Na+, Cl-, Mg2+, OH-) and reassemble as different compounts, i.e. magnesium chloride (MgCl2) and sodium hydroxide (NaOH). In this case, the first pair of chemicals were the reactants, and the last two were the products. However, this reaction could happen the other way as well, starting out with magnesium chloride and sodium hydroxide as reactants, and end up with sodium chloride and magnesium hydroxide as products.
The entire reaction could be written as:
2NaCl
+ Mg(OH2) ⇌ MgCl2 + 2NaOH
the double arrows symbolising that it could go in either direction, in theory.
A general equation would be:
A
+ B ⇌
C + D
A, B, C and D symbolising different compounds. Depending on the direction, the reactants could be either A and B, or C and D, and the products would be the other pair.
I hope that is simple enough to grasp. Let us move on to the critical point.
Most biological reactions are so slow that they would not naturally occur during an organism's lifespan, so they require catalysts that accelerate the process. Now, consider what would happen if only one direction of the reaction is catalysed! The reverse would be so slow that it is unlikely to occur in the near future, and the reaction thus becomes stable.
I'm nut sure I quite understand the implications (deeper meanings) of this view on how life aims for stability. It seems the dynamic kinetic stability still requires the release of energy. However, the mechanisms and 'purpose' behind this other form of stability seems to be more selective, almost like evolution by natural selection toward a more stable state (higher complexity). But I am reading the papers as I'm writing this (just couldn't wait to share!), so I hope that by the end of it, it will be clearer what this new isnight means.
I hope that is simple enough to grasp. Let us move on to the critical point.
Most biological reactions are so slow that they would not naturally occur during an organism's lifespan, so they require catalysts that accelerate the process. Now, consider what would happen if only one direction of the reaction is catalysed! The reverse would be so slow that it is unlikely to occur in the near future, and the reaction thus becomes stable.
I'm nut sure I quite understand the implications (deeper meanings) of this view on how life aims for stability. It seems the dynamic kinetic stability still requires the release of energy. However, the mechanisms and 'purpose' behind this other form of stability seems to be more selective, almost like evolution by natural selection toward a more stable state (higher complexity). But I am reading the papers as I'm writing this (just couldn't wait to share!), so I hope that by the end of it, it will be clearer what this new isnight means.
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