• Question: you know people say \'the sunlight, water, CO2 and mirerals go to the leaf and PHOTOSYNTHISIS HAPPENS, then energy and oxygen comes out\' what actually happens when photosynthisis happens? because there must be something, instead of it all comes together and then POOF. don\'t leave out sciency words, im sure i\'ll get the idea :).

    Asked by micromil601 to Antonia, Douglas, Hugh, Matt, Tom on 19 Jun 2010 in Categories: .
    • Photo: Matthew Hurley

      Matthew Hurley answered on 13 Jun 2010:

      Photosynthesis specifically refers to the way that carbon dioxide (CO2) and water (H2O) are brought together to make carbohydrate sugar (CH2O) and oxygen (O2). The light energy is the energy that causes this.
      At the same time the light energy (from the sun) is used by the energy molecules NADP and ADP to make ATP (by the shuffling around of electrons and protons). ATP is the energy molecule that all living creatures (including us) use to transport energy.

    • Photo: Antonia Hamilton

      Antonia Hamilton answered on 14 Jun 2010:

      I’m not sure I can give an explanation in the time available, but the wikipedia page on photosynthesis shows the main chemical reactions. It isn’t just a big POOF, it is a whole series of carefully balanced chemical reactions called the Calvin Cycle

      http://en.wikipedia.org/wiki/Photosynthesis
      http://en.wikipedia.org/wiki/Calvin_cycle

    • Photo: Hugh Roderick

      Hugh Roderick answered on 17 Jun 2010:

      It certainly isn’t a case of poof! Within any plant cell that is green are structures called chloroplasts and they are made up of tightly coiled membranes called thylakoids that contain the pigment chlorophyll that absorbs light in the blue and red spectrum and reflects green (which is why plants appear green). What happens in the chlorophyll pigment molecule when it has absorbed the light is that electrons become excited and this excitation is passed across several molecules associated with the chlorophyll and it’s energy is then used to create a molecule called NADPH that carries energy into the Calvin cycle, which is the process that plants use to make new compounds like the building blocks of proteins. The excitation of the electron in the chlorophyll causes a chemical reaction in which water is split into hydrogen and oxygen molecules so that the excited electron that passes out of the chlorophyll to create the NADPH can be replaced. The hydrogen from that reaction is then pumped through a protein complex that causes an ATP molecule to be formed. ATP is used in almost all reactions in the plant cell as a source of energy.

      That’s as concise as I can get it, and I can’t vouch for it’s accuracy as it’s a long time since I was taught it! Hope it makes a little sense!

    • Photo: Douglas Blane

      Douglas Blane answered on 19 Jun 2010:

      OK, good question and sorry it’s taken me a couple of days to answer. I got sent away on assignment.

      This is the most important chemical reaction in the world. It’s what keeps producing the oxygen that all animals, including us, need to breathe.

      But it’s also one of the most complicated. If it wasn’t we’d be making energy from sunlight as easily as plants and trees do. And we wouldn’t have an energy problem.

      Basically in photosynthesis there are two separate reactions. The first is called the light reaction and the second the dark reaction (or sometimes the Calvin Cycle).

      So what happens? Well light from the sun has all colours in it. When this light hits chlorophyll in the leaves, it hangs onto the red and blue light and not the green. That’s why plants that photosynthesise look green. Funnily enough it’s because they’re not using the green light.

      So anyway, light has energy and the chlorophyll uses the energy in the red and blue light to make a molecule called ATP (short for adenosine triphosphate). There’s a lot of energy locked up in that ATP. It’s a wee power pack.

      That’s the light reaction. In the dark reaction – so called because the plant can do it in the dark – the plant uses the power pack it produced earlier to build a simple sugar. This is called glucose and it’s made of carbon, oxygen and hydrogen atoms. The plant gets those atoms out of carbon dioxide (CO2) and water (H2O) molecules.

      Between them these have a bit more oxygen than is needed to make the glucose though. So the plant just lets that go. That’s where all the oxygen we breathe comes from.

      I’ve been looking for a good movie that would show you how it works, because that’s always easier to follow than just words. There are a lot of them out there. This is one I like. Let me know if you do. http://www.5min.com/Video/The-Calvin-Cycle-150947894

Comments