It’s been almost a year since we (re)launched Science as We Know It. Our first post was a small imagination exercise where we pretended a cell was a city and drew some metaphors about what each cell organelle might be comparable to. You can (re)read all about it here.
At the time, some additional interesting parallels were worth exploring. However, in the interest of length, we kept them archived… Until now.
Welcome to What If a Cell Was a City #2 – Energy and Trash. This sounds exactly like the title of a movie sequel, doesn’t it? Well, movie sequels tend to be worse than the originals. So, let’s see how this one goes.
Mitochondria – The Powerhouse Of The Cell
We are aware that calling the mitochondria the powerhouse of the cell is such a cliché. But, given that this comparison is used so many times, do people actually know why it is so?
To produce energy we need to eat food. Us, other animals and even smaller organisms. But the energy that exists in food cannot be used directly by our bodies. Proteins, fats, carbohydrates… All these nutrients come down to one single type of energy, a kind of energy “currency” called ATP: adenosine triphosphate (bless you).
The “industrial” process that takes place in the mitochondria can be resumed relatively simply: glucose (from food) + oxygen (that we breathe in) = carbon dioxide, water (that we breathe out) and energy (in the form of ATP).
ATP is then, just like electricity produced in a city’s power plant, used throughout the cell for any activities.
Muscle cells need to move? -> ATP!
Heart needs to beat? -> ATP!
Sperm cells need to wave their little tails to swim until the egg? -> ATP!
Chloroplast – The Greenhouse
If the mitochondria are the pollutant coal power plant, the chloroplast is the environmentally friendly renewable energy power plant, with (almost) zero carbon footprint. However, it does not exist in every cell. Animals, for instance, are not lucky enough to have one. Mostly plants and algae do.
The chloroplast is the place where photosynthesis happens. It is green because of chlorophyll, the pigment that is key to “absorb” the energy from the sun which is then used to make “food”.
The energy coming from sunlight is converted into energy (yes, our boy ATP!) which is then, together with captured carbon dioxide, turned into carbohydrates and oxygen. That’s the reason why plants are so important: they release oxygen and produce carbohydrates!
And, if you ever worried about your diet, you are probably aware that carbohydrates mean sugars. And if you ever have breathed in your life, you are aware that oxygen is good. Food and oxygen! Plants produce food and oxygen!
Too bad chloroplasts only exist in plant cells and algae, though. If we had them, we wouldn’t have to worry so much about actually eating. On the other hand, it is quite sad… Don’t you think plants are missing out on such amazing things as steak… Tropical fruits… Chocolate…?
Lysosome – Recycling Centers
A side effect of the industry and activity in any city is, of course, trash production. Whatever things we use and stuff we do, there will always be waste materials that we need to get rid off. And the same happens inside our cells.
Lysosomes are vesicles that incorporate complex molecules that are not needed in our cells. Inside lysosomes, the pH is low (so it is acidic) which helps with, together with other enzymes, the degradation of the molecules inside. Similar to what happens in the stomach, these contents are degraded inside this kind of waste-disposal center.
And then, since our cells run on a sustainable economy, many of the products resulting from this digestion are brought back to the cell to be used to synthesize other components. Our cells might be a confusing city, but they for sure are environmentally friendly.
And here it is, after having a look at how the industry of protein production happens in our cells last year, we showed you today how our cells produce energy and recycle waste materials.
If I were you, I’d stick around for one more year. Who knows what metaphors we will think about next year!