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Thread: Energy for Photosynthesis

  1. #1 Energy for Photosynthesis 
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    When writing about photosynthesis in bacteria I wrote:

    They can do this in one of two ways. Photoautotrophic bacteria collect energy from light, while the less common chemoautotrophic bacteria get energy through oxidation of a chemical source, such as nitrogen, sulphur or other elements.

    Now that I have moved in a sense up the tree of life to talk about the same process in plants I am having difficulty confirming that all plants get the energy for photosynthesis from sunlight. In other words, that there are no chemoautotrophic chloroplasts in plants.

    Can anyone help out there at all?


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  3. #2  
    Forum Cosmic Wizard paralith's Avatar
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    The very word photosynthesis implies that light is required. Chemoautotrophs, then, are NOT using photosynthesis. A chloroplast is a photosynthesis specific organelle. It does not create energy via any other process.


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  4. #3  
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    Okay, let's put that down to a poorly worded question. So here's another try:

    Some bacteria are capable of a process that uses an external energy source to convert hydrogen and carbon dioxide into carbohydrates and oxygen. Some of those bacteria get the energy for this process from the sun and some obtain their energy from chemical sources.

    When talking about the same or similar process in plants, is it true that all plants obtain their energy for this process from sunlight, and that no plants at all obtain the energy for this process from chemical sources?
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    Quote Originally Posted by numbers
    Okay, let's put that down to a poorly worded question. So here's another try:

    Some bacteria are capable of a process that uses an external energy source to convert hydrogen and carbon dioxide into carbohydrates and oxygen. Some of those bacteria get the energy for this process from the sun and some obtain their energy from chemical sources.

    When talking about the same or similar process in plants, is it true that all plants obtain their energy for this process from sunlight, and that no plants at all obtain the energy for this process from chemical sources?
    There are no chemoautotrophic plants, if that's the answer you are looking for.

    Plants have no mechanism besides photsynthesis by which to be primary convertors of external energy into usable chemical energy for themselves. I use the word primary because, as I'm sure you will appreciate, symbiotic relationships and predatory relationships all use chemistry instead of light, but they're not primary producers of the usable energy.
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  6. #5  
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    Quote Originally Posted by sunshinewarrior
    There are no chemoautotrophic plants, if that's the answer you are looking for.
    That is exactly the answer I was looking for.

    Thank you very much indeed.
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    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
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    There is a class of proteins called bacterial rhodopsins which are light powered ion transporters, some of which are used by halobacterium to generate the proton motive force use for ATP synthesis. I had a lengthy argument over this once in an evolutionary biology class, where the evolutionary bio prof didn't consider this photosynthesis because no glucose was being produced, though a micro prof I spoke to did consider it to be photosynthesis. After all, the bacteria is synthesizing ATP.

    If you really want to get into bacterial photosynthesis, there are 4 main types Purple non-sulfur, purple sulfur, green non-sulfur and green sulfur bacteria that do photosynthesis. Despite the names they don't always appear in those colours , each has a different photosynthetic system that relies on bacteriochlorophylls. These guys each specialize in a different wavelength of light so they often appear in stratum in watercolums. They are also anoxygenic, unlike cyanobacteria, algae and plants.

    Then you have cyanobacteria which are likely the source of chloroplast since they use the same photosynthetic system as plants and contain thylakoid membranes
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    There actually are non-photosynthetic plants. Lathraea clandestina, Orobanche elatior, and Orobanche lutea are all plants that have lost the ability to photosynthesize and now survive as parasites on other plants. These organisms still produce plastids, but not chloroplasts.
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    Add to this photosynthetic animals, out of an interest in being thorough.



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    free radical
    Add to this photosynthetic animals, out of an interest in being thorough.
    Except these are not really photosynthetic animals per se. They obtain the chloroplasts from the algae. Perhaps someday evolution will drive these sea slugs to maintain chloroplasts and inherit them as another cellular organelle.
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  11. #10  
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    It's all part of the story.

    And, they can survive for upwards of a year, without ingesting anything, from energy derived from those chloroplasts.
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  12. #11  
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    Quote Originally Posted by chadn737
    There actually are non-photosynthetic plants... that have lost the ability to photosynthesize and now survive as parasites on other plants.
    This is both interesting and useful, thank you. I have an upcoming section on parasites and specific examples will make it more interesting. These have the added bonus of being examples that not all plants photosynthesise, which I would probably have assumed from an earlier post in this thread. Thank you.

    Quote Originally Posted by free radical
    Add to this photosynthetic animals, out of an interest in being thorough
    I'm not sure that the emphasis is on being thorough. What I am more interested in is simplifying to a level my audience can understand whilst still being right. There is nothing worse, IMHO, than an over-simplification, analogy or metaphor that is plain wrong just because it's easier to explain than being right. For that reason I prefer examples that both illustrate my point and help dispel misleading assumptions my audience might draw. And in that context, the "solar-powered" seaslug is a very useful example, thank you very much.

    Looking at the website you link to I read in the text where it says of the algae: It has a multinucleated cytoplasm Does that mean what I think it means, that each cell has more than one nucleus? Is this common?
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  13. #12  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by numbers
    Looking at the website you link to I read in the text where it says of the algae: It has a multinucleated cytoplasm Does that mean what I think it means, that each cell has more than one nucleus? Is this common?
    It is quite common. The structure is called a syncytium.

    It is also demonstrated in astonishing individual organisms like slime moulds, that can be considered the largest 'single' cells on earth...


    Edit:

    Web resourcesare fine and dandy, but nothing beats a good book, say I. Try Colin Tudge's The Variety of Life for wonderful discussions on syncytia, chemoautotrophy, cladistics and much more besides.
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