What separates living from non-living?
3 Answers
Well, an easy answer is composition of cells.
Explanation:
Living things are composed of cells, which use chemical processes (like respiration and excretion) to stay alive. They are also "living", meaning they can make their own choices on what to do and not.
Non-living things are not composed of cells. They do not perform "living" tasks like respiration, excretion, reproduction, etc.
Another thing is that living things are classified into kingdoms, phylums, classes, etc., while non-living things are not.
There are animal kingdoms for living things but there isn't a "non-living thing" kingdom for non-living things.
Living things can "die", while non-living things cannot.
Those are some examples I can think of.
Metabolism...
Explanation:
Metabolism is the incredibly complex total of (bio-)chemical reactions that take place in any living organism 24 hrs a day, 365 days a year.
These reactions willl take place in Nature as well, but often at a MUCH slower pace.
In a living organism, these reactions are (nearly always) catalysed by Enzymes . These catalysts are highly efficient, usually VERY specific for their substrate(s) and VERY fast.
But, like any catalyst, they don't alter the equilibrium of the reaction.
So why are they there, and how can they enable "life" ?
The secret lies in the interrelations between the various reactions:
Let us assume that there is an enzyme that converts A to B:
But, nearly always the reaction is reversible:
So, in reality the following takes place:
Let us assume that the equilibrium for this reaction lies in the middle. In that case, once there is 50%
An Enzyme that catalyses this reaction will certainly speed it up, but will NOT change the point where the equilibrium lies: 50/50 .
BUT!:
If in a follow-up reaction
As
The continuous depletion of one, more or (usually) all of the products from a reaction will keep driving this reaction forward, depending on the availability of the substrate(s) and the catalyst.
To complicate things further, regulatory processes like Gene Induction/Repression, pH- and Temperature Control etc. have their effect as well, resulting in an incredibly complex aggregate of reactions that, at first glance, seem to defy Mother Nature's laws...
The system as a whole is pretty robust and can take a hit or two, but there are some spanners that can be thrown into the works, making the whole thing grind to a halt.
Examples:
This blocks enzyme complexes in the respiratory chain that use Oxygen.
Same effect, blocking Oxygen uptake.
Same effect, blocking Oxygen uptake.
Etcetera....
The Biochemical Pathways that enable "life" have over the years been studied, documented and collated. The initiative was taken in the 1960's by dr. Gerhard Michal and his research group.
This has resulted in a map that shows (human) metabolism in all its complexity, and how all paths are connected. To give you an idea about the complexity, have a look at part of this map:
Pretty unreadable I know, so here's a link to the on-line version:
http://biochemical-pathways.com/#/map/1
Actually there are two, one for Metabolic Pathways and one for Cellular and Molecular Processes. As Science progresses, these maps are regularly updated.
Custody of the maps has passed between various companies over the years, and at present is in the hands of Hoffman-laRoche .
Printed copies are usually handed out for free at their stand in Science Fairs (at least they were in my time ), and you CAN ask for them on-line, though I gather it would help if you can convince them you are seriously involved in life sciences (e.g. being a student).
The on-line, interactive version was made available in 2014.
Finally, the Instigator, dr. Michal :
There is no life outside the cell. Cell controls living organism thermodynamically. It genertes energy from food molecules and spends energy conservatively. When it stops generating and spending energy there is death of the cell.
