How can some things like apples, cucumbers or the human body can contain so much water (86%, 96%, 60% respectively), but obviously not be in a mostly liquid state? How isn’t the minority of solid matter floating around in all that water?
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The solid matter are the outside of the cell. The inside of the cell is mostly water. Then there’s blood in animals, which is mostly water.
Have you ever seen a sandbag pile? Sand is grainy and doesn’t form ‘solid’ structures. Put it in a bag and suddenly it can’t move very far. You can build walls with it. Glue those sandbags together and you can create solid objects.
Basically cells are like water balloons. A water balloon is mostly water, but a bathtub full of water balloons doesn’t slosh around.
The bathtub full of water balloons is mostly stable.
Now add another layer to your water balloon structure: some glue between the balloons. If the balloons are glued together, even imperfectly, you can take away the bathtub and the mass of balloons stays intact.
Now if you add one more wrinkle is that you put some sticks inside the water balloon mass. The sticks run between the balloons at random angles and they connect balloons far away from each other together. Think of it like a tight webbing holding it all together. Now not only is the structure stable in the sense neighbor balloons stay next to each other, but it’s got some rigidity in that if you try and squash it one direction, it won’t squash because it refused to expand in the other direction (the sticks are adding tensile strength).
That’s basically the structure of a multicellular organ that’s mostly water: the water balloons are cells, and the glue between balloons and the long sticks adding tensile strength (which keeps structures relatively rigid) are the extra cellular matrix.
Also plant cells, like some bacteria, have **cell walls** so their cells are more like styrofoam boxes than they are like water balloons.
The water balloons-plus-glue model is a better model of a squishy tissue like animal flesh, but it’s essentially what an apple is too.
Think each cell as an apartment in a building. The building is strong and stable, but the inside of each apartment is mostly empty space.
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