If I had a microscope that could see atoms and molecules, how far out would I need to zoom before I could tell I was looking at life?
I’ve heard things like “people are 70% water” but water is not alive.
I’m asking in chemistry because I’m not sure if life at a molecular level is considered biology.
In: Chemistry
The level of cells is where it would become really clear. Beneath that you could see proteins, which are complex and interact with each other in interesting ways, but a cell is the building block that grows, eats, moves at least a little, and makes copies of itself. I feel like that’s recognizable as “life-like”.
You could try to argue for nucleic acids, which have the ability to replicate and carry complex information, but that alone might not suffice and they need outside help (which cells provide) to successfully copy themselves, and to actually use the genes they carry.
Well, at molecular level you can recognize life by the hyper complex molecules that defy the logic of what you’d expect to see from chemistry alone.
For example our DNA string is a single molecule, 3 **billion** base pairs chained together, something that would never happen if you just randomly mixed the ingredients.
And then you see an identical string a tiny bit to the left, exactly the same type of atoms in the same order in another long string
You see complex protein machines doing jobs, all also a single molecule that got assembled from a partial copy that genetic string. Some like motor proteins basically carry stuff while “walking” with some simple feet that are part of the same molecule
This is very difficult to answer, because how do we define life? Would having active cellular processes count as being alive? Would the cell have to perform a full range of life processes for it to be counted as living?
You could watch a sperm cell swimming around, for instance, but although it’s an alive cell it isn’t a living organism.
Zooming in to a cell’s membrane, you could watch proteins such as ion pumps, powered by energy made by the cell in the form of ATP molecules, do their thing. At an atomic level, you could see ions being pumped through, but we could fake that in a lab by artificially supplying ATP and ions. Likewise, we could look at DNA being transcribed or proteins being manufactured within the cell, but we can do that in the lab too using modified cells that aren’t really alive.
I think the smallest thing you could measure that you could undoubtedly say was life would be the smallest living organism, the single-celled [*Nanoarchaeum equitans*](https://en.wikipedia.org/wiki/Nanoarchaeum_equitans) at 400nm, as it’s the smallest thing that can do everything we associate with life (movement, respiration, growth etc.). Even then, it has to live inside a larger single-celled organism as a parasite as it’s missing a lot of normal cellular processes!
I think your question may be more rooted in philosophy than chemistry or biology.
**Tldr**: Life is an emergent property above the molecular level. You need a number of complex molecules working together to create it.
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“Life” as we generally understand it only exists a level higher. There is nothing at the molecular level that has all the hallmarks of life, one of the definitions being “any system capable of performing functions such as eating, metabolizing, excreting, breathing, moving, growing, reproducing, and responding to external stimuli”. Though, *exact* definitions vary.
You can mix some molecules together however, and start reaching these qualities, but that hits the field of microbiology, cell biology (my field), and so on. You see, life is an emergent property–a quality or characteristic that can only exist as a *greater than the sum of its parts* arrangement. If you continuously break it down, eventually it no longer exists among its separate parts.
One of the classic transition points of life (because it’s frequently debated on whether or not it is alive) are viruses. Viruses are, essentially, DNA/RNA packaged by a handful of proteins, that code for little else except the machinery to make more DNA/RNA and proteins to make more viruses. That’s it. And this strand can be as short as only a few thousand base pairs, as opposed to human genomes’ billions of base pairs. Viruses lack some of the criteria of life, but replicate themselves *using* their hosts, as if they were a tag-along that achieve qualities of life largely by borrowing them.
Go further up from here, and you have cells which we all agree *are* alive. Go below, and you have individual molecules which we do not consider alive, despite having activities that when put together start becoming life.
I have seen a nice enough explanation from Kurzgesagt that tackles this subject: [https://www.youtube.com/watch?v=QOCaacO8wus](https://www.youtube.com/watch?v=QOCaacO8wus)
Long story short, the world, the universe, at any level, moves towards equilibrium, a state that is uniform and nothing changes anymore (eg. if you leave a hot cup of tea at room temperature, it exchanges temperature with the room air until it reaches the equilibrium temperature, which is room temperature tea).
Life is when there is a system that actively fights “getting to equilibrium”. The cell does that by getting stuff in, convert it to energy, produce some side-stuff in the process, and using that energy to move around and bootstrap this process again and again, while also gathering enough stuff from around it to multiply.
For living organisms, the “equilibrium” within their environment is … well… being dead, as it no longer actively fights the equilibrium and is slowly decaying, moving towards the environment.
You probably wouldn’t have to zoom that far out to see some complex molecules and processes. Here is a very cool [molecular animation of processes inside a cell](https://youtu.be/wJyUtbn0O5Y), each little blob is a molecule that probably represents several to hundreds of atoms. The space between would be full of water molecules but they are left out of the animation so you can see what’s going on.
This is a very loaded question.
Everything in the universe is made up of atoms (elements that you’d find on a periodic table). For instance: Hydrogen is an element, so is oxygen.
When atoms are combined they are called molecules. So, 2 individual Hydrogens attract to a single oxygen atom, creating a single water molecule (which is 3 atoms = 2 H + 1 O). In this example, they attract like magnets (here, it is called an ionic bond).
So, atoms have charges that allows them to bind to other atoms, or repel atoms, again, think of atoms as tiny magnets. Some have positive charge(s), others have negative charge(s). If you were to combine 1H atom to another, you get Hydrogen gas, which is explosive.
When molecules are combined, you have compounds.
EVERYTHING, living (person) or inanimate (rock), is made up of atoms/molecules. Organically (pertaining to life/carbon), the common elements are Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus and Sulphur.
Don’t think in terms of biology or chemistry. It’s all the same. (If you want to get technical… in biology and organic chemistry the focus is mostly on those 6 elements listed above, as they are mostly involved with life and metabolic processes. The concepts remain the same.)
All molecular means is that it is broken down to its most basic form. I.e a bucket of water vs 1 molecule of water. It can go the other way too: 1 molecule of water can be broken into Hydrogen (gas) and Oxygen (radical) via a process called electrolysis.
As people, we are made up of cells, cells are made up of molecules, which are further broken down to atoms. This holds true for everything…water, blood, food, textiles, metals….everything.
Alloy (Brass or Steel) = Combined metal atoms like tin, aluminium, zinc, copper, gold, silver, etc.
At most superficial, when our blood is taken…It then separated into components, to help diagnose disease. Then tests get more and more specific to narrow down the diagnosis. This determination often breaks things down to the molecular or cellular level because processes need to be assessed.
Hope that didn’t confuse you more.
Unless you have a super fancy million dollar microscope, most biological processes need to be stopped in order to observe under a regular microscope. It’s usually the stains, fixatives and impregnation that enable the visibility that shut down these very processes.
This is a very good question. There is a definition for live and with this definition a virus is not a living being. The border between so called live and just chemistry is fluid. Not a single molecule in our body is at live. But the whole body is. There is no scientific answer to that it’s philosophic.
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