To my understanding, water has no nutritional value. It has nothing in it. It’s simply just water.
That said, why is it so crucial to life?
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Trying to fuel any biological functions without water would be like trying to run an internal combustion engine without petroleum products.
It’s the basic medium that every living thing functions on and is made of.
>why is it so crucial to life
You answered it: it’s “empty” and serves as the perfect medium for all sorts of biochemical processes.
Then, life evolved based on abundant resources and water just happens to occupy 3/4 of the surface. If we lived in another universe where oil or lava is more abundant, we’d be oil or lava-based, too.
Take a spoonful of salt or sugar and stir it in. It’s waters ability to be a “universal solvent” (that is, it dissolves stuff well) that makes it special.
It allows chemicals to mix a stir and combine. Technically it doesn’t have to be H2O but any liquid chemical like liquid nitrogen or methane can mix and stir but those are to cold to allow any kind of chemical reaction that can produces heat. So ONLY water has this ability to stir and allow chemical reactions..
The reason water is so good at dissolving stuff is because it is a ***polar*** molecule. One side has a small positive charge, the other a small negative charge. This simple fact basically makes life here possible.
It’s polar because it’s shaped like a boomerang. If the atoms were in a straight line it wouldn’t be polar.
Is this r/asklikeimfive? No offense op but this seems like your basic education failed you.
>To my understanding, water has no nutritional value. It has nothing in it.
You are ranking things important to ‘life’ by their nutritional value which is not the best way to think of them
Water has limited nutritional value to humans yes, but in terms of chemistry and what it can do, it’s incredible
Water can act as a solvent (it dissolves things into liquids) for a wide range of chemicals/foods/objects which is incredibly useful for life (there is a quote that if humans weren’t made of water, then we would find it the most terrifying thing in existence),
In the most basic sense, for complex life to occur, you need lots of little things to mix together, and water is the thing that lets this happen, solids and gases are difficult to mix or require a lot of things in place before controlled mixing takes place, but mixing liquids is fairly straightforward in comparison, so most of life uses mixtures of liquids, and water is the best thing to use to get things into liquid in order to mix in the first place (some of the simplest organisms exist and survive in liquids for this reason)
Because we (humans, or any animal really) need to dissolve anything we eat to get the nutrients etc. from them, we need something to help break down our food, and water dissolves things enough that we can break down the food, but it doesn’t dissolve things so fast that they become unusable before our bodies can metabolise them
We do this (metabolization) by either breaking the larger/complex molecules in the foods down into smaller molecules or making larger molecules from the smaller ones – our bodies use water for this process (vastly oversimplified) without metabolization, complex life most certainly wouldn’t exist
Because so many things can be dissolved in water, then while a glass of water from a tap may have little in it of nutritional value to humans (or ‘nothing’ as you broadly state), somewhere like the Atlantic Ocean, the water has a *lot* of things floating in it that are essential for aquatic life (dissolved oxygen, various ions, salts etc. that marine life has evolved to take advantage of), and plant life (including photosynthesis, where the hydrogen and oxygen in water is crucial for making glucose alongside carbon dioxide from the air)
TL:DR water is used to make the nutrients that plants and animals need to survive, without it then life would be very different
99.99% of life on Earth is based on photosynthesis to extract carbon and hydrogen from the non-living environment, and that needs (liquid) water:
CO2 + H2O + sunlight + some dirt -> free oxygen + self-replicating biomass with stored energy
What other liquids are like water?
If you were going to chose a liquid to base life around it would be water it’s the best solvent and forms polar bonds which are a nice mix of covalent and ionic. The atoms that make it are hydrogen which has the highest energy density and oxygen which is one of the most available oxidizing agents. They interact in interesting ways with carbon which is pretty much the atom you would base life around given a choice because of the different ways it can bond to itself. However probably the main reason is the life you know evolved on a planet with liquid water. It would be no surprise if life coming from planets with ammonia seas was ammonia based.
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