Photosynthesis involves chlorophyll pigments, redox proteins, NADPH, the Calvin cycle…. wait, where did everyone go? You’ve gone haven’t you? Will you stick around if I just cut out the rubbish and get to the bits that matter? Deal? Great!
Everything that happens on this planet happens because of sunlight. Energy flows through our planet like a river. It comes in as light, leaves as heat, and somewhere in between it drives every single thing on Earth. The rushing wind, pouring rain, fluffy clouds, winter, summer and of course LIFE all come down to sunlight.
But wait, people aren’t solar powered! We eat food (sugars, proteins, and fats) that supplies the energy we need to play football, write a blog post, or run in the opposite direction from someone who might try to talk to you about science. If you’re feeling a bit drained, you can’t just stand in a field and absorb a bit of light energy… but plants CAN! And the way they do it is called photosynthesis.
Photosynthesis is the gateway through which that river of energy from sunlight pours into the great circle of life.The laugh of a child, the flutter of a butterfly’s wings and the roar of a lion. Just like a raging river, sunlight is always moving (at about 300 million meters per second to be precise). It’s here and then it’s gone. Now we’ve got a problem. To survive, all living organisms require a constant supply of energy every second of every day. Even if plants could live directly off that river of light, what happens at night, or in the dead of winter, or on any of the 364 days of the year in England when the sun doesn’t shine? They need to trap it.
Plants need to be able to dip a bucket into that river of light, fill it up, and keep it aside for later. How? Photo(light)-synthesis(making). Making what? Plants reach out and grab carbon dioxide from the air and water from the soil and use them to build their “buckets” of energy, namely sugars, fats, and proteins. This energy is then locked into the bonds between atoms of carbon, hydrogen, and oxygen. Light energy has now been trapped as chemical energy that the plants can store until they need it. Oh, and in the process they spit out a bit of oxygen as a waste product… cheers plants!
OK. So what’s this got to do with the laugh of child, the roar of a lion, blah blah blah? Well, that lion eats a zebra and steals its energy buckets (sugars, fats, proteins). Of course the zebra had just nicked those buckets of energy by eating . . . you guessed it . . . Plants!—which of course used photosynthesis to pour light energy into those buckets in the first place. Humans are just like the lions except we’ll eat anything—plants, other animals, even Marmite.
Now there’s no point in stealing those buckets of energy if we can’t empty them back out when we need them. And that’s called respiration which would take me AGES to explain. Take photosynthesis, turn it around, and run it backwards. That’s respiration. Actually, that didn’t take long it all!
So, the next time you’re in the shops, peering at the calories on the back of a packet of biscuits, just remember, those calories (energy) come from those little photosynthetic buckets: sugars, fats and proteins. When you’re counting those calories, you’re counting rays of sunshine. And when that burst of chocolate rolls across your tongue, you’re tasting starlight. Nice one plants.
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Leaves Photograph from www.flickr.com CC-by
Illustrated Diagram from en.wikipedia.org CC-by