How does cells get food?

osmosis experiment

Have you checked out the egg experiment where we managed to get the shell disappear?

Click here for that experiment

Well, that magic clearly figures out that with the eggshell gone, it was pretty much the next layer, the egg membrane that holds that whole-cell together. I have read about animal cells and it means that was how an animal cell is. A bit jelly-like, a bit wobble and a whole lot jiggly. This got me interested. I wanted to know how food gets in and out of this? I do agree the egg has its own food the yolk, but what about our cells, they don’t have a yolk.

Thanks to Mum learnt biology all her college years she helped me set up an experiment to show that they get things from outside. Yes, I did roll my eyes too when she said this. I know we have to eat, but how does the cell get what it needs to eat? Usually, I don’t have trouble imagining up things, but this, no way.

Here is what we did.

To set up

  • 1 clear glass, so we can see what is going on.
  • 1 jelly egg (check link above)
  • any water soluble food colour of your choice
  • 1/2 glass of water

Fill the glass with water 1/2 of the way. Put a few drops of the food colouring in the glass and stir well. Carefully roll the egg into the glass without damaging it.

Put a lid on the glass and leave it overnight. Come and check the egg in the morning. You can see that there is a yellow outline of the yolk and the rest of it for me was all green. Wait, now I need to know if the green colour had got inside the egg. For this, I had to tear open the egg membrane. So we tore it open and guess what, the white of the egg which was clear yesterday had become green. The yolk stayed yellow. the green bag like bit is the membrane. So the green liquid from outside managed to get inside the egg.


What is happening here?

When you have liquids of two different concentration and connected the particles move so that both the liquids will finally have the same concentration. This is called diffusion. When this happens through a membrane ( like the egg membrane) it is called osmosis. ( source)Now the membrane is the one that decides what should go through and what should not. Kind of like my mum watching and then stopping when it is the 10th time I reach for the cookie jar. Osmosis is the way plants and animal cells get food and water.  So the membrane decides what should pass through and how much. Now that is a cool science fact.

When we did this experiment, it made me realise, no wonder the egg placed in the vinegar, in my first experient appeared swollen. It must have taken in a lot of liquid to swell up. That too is osmosis.

I am now curious to set up another where the egg will give out its liquid and shrink, Do you think that is possible?

Let me know if you know how to set it up.

Do read up on the experiments I did so far and write to me what you have tried.

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