Notices
Results 1 to 14 of 14

Thread: Heavy oxygen in water question

  1. #1 Heavy oxygen in water question 
    Forum Freshman nerd_girl's Avatar
    Join Date
    Oct 2008
    Posts
    12
    Okay, I'm stumped guys. I looked everywhere online, can't figure it out. It's for my open university course so I don't have lots of sources to go to other than my book and online...doesn't help me.

    The question is, in a suspension of Chlorella they're added heavy isotope of oxygen 18O2 and regular isotope of oxygen 16O2

    [They show a chart of the heavy oxygen being in steady decline, while the regular oxygen increases during light and decreases during dark]

    1) Why is there a decrease of heavy oxygen isotope concentration in both light and dark?
    2) Why is there an increase in the regular oxygen isotope concentration in the light, and what is the source of of the isotope?

    Please help, I'm totally flummoxed. :?

    -nerdgirl


    Reply With Quote  
     

  2.  
     

  3. #2  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    I suggest reading about aquariums and what causes the oxygen levels to increase or decrease there.


    Reply With Quote  
     

  4. #3  
    WYSIWYG Moderator marnixR's Avatar
    Join Date
    Apr 2007
    Location
    Cardiff, Wales
    Posts
    5,760
    not sure if this is really helpful, but a google search for "chlorella oxygen isotopes" brings up the following paper : Origin of the chlorophyll b formyl oxygen in Chlorella vulgaris., which seems to indicate that O-18 gets incorporated in the cell structure of Chlorella, which would explain why it happens both in light and dark conditions
    the increase of O-16 in the light is probably the normal chlorophyl reaction at work ?
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
    Reply With Quote  
     

  5. #4  
    Forum Freshman nerd_girl's Avatar
    Join Date
    Oct 2008
    Posts
    12
    Thank you guys, that helps a bunch

    -nerdgirl
    Reply With Quote  
     

  6. #5  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    Quote Originally Posted by nerd_girl
    Thank you guys, that helps a bunch

    -nerdgirl
    Okay, nerdgirl, how are you going to answer the question? Because I wanted to give my answer but not until you had finished your homework. It's a little different than what Marnix wrote.
    Reply With Quote  
     

  7. #6  
    WYSIWYG Moderator marnixR's Avatar
    Join Date
    Apr 2007
    Location
    Cardiff, Wales
    Posts
    5,760
    remember that i have no expert knowledge of this subject whatsoever - i just try to deduce from what little knowledge i have + what i can find from searching the internet

    i would not in the least be surprised if harold proves my conclusion gloriously wrong
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
    Reply With Quote  
     

  8. #7  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    Quote Originally Posted by marnixR
    remember that i have no expert knowledge of this subject whatsoever - i just try to deduce from what little knowledge i have + what i can find from searching the internet

    i would not in the least be surprised if harold proves my conclusion gloriously wrong
    One of the real biologists will probably be coming around shortly to slap us both around.
    Reply With Quote  
     

  9. #8  
    Forum Freshman nerd_girl's Avatar
    Join Date
    Oct 2008
    Posts
    12
    The thing is we never studied about this topic in class, nor can I find anything in the textbook. I think the second question is easy and I think I got it right, but there's nothing about heavy oxygen with chlorella anywhere online (I tried to google that information too)... I think it's a bit of a ridiculous question frankly and it's very hard to get a hold of a teacher in the open university..and I gotta submit an answer by tomorrow anyway so I figure no point fussing about it just ask you guys. I did write something down..not sure if it's correct at all but better than nothing :?


    -nerdgirl
    Reply With Quote  
     

  10. #9  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    I don't think you need to know anything specific about Chlorella to answer this one. When you googled aquariums and oxygen, what processed did you find that caused oxygen to decrease in the aquarium? Which of those would apply to your suspension of algae in water?
    Reply With Quote  
     

  11. #10  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    I guess nerd girl has turned in her homework by now.

    My answer is that the dissolved oxygen, whether it is heavy or regular oxygen, is continually depleted by plant respiration and decay of dead cells. This happens in both light and dark.

    The increase of oxygen-16 during daylight is due to photosynthesis. The new oxygen is coming from dissolved carbon dioxide, not the dissolved oxygen, and so it is the regular oxygen-16 isotope.
    Reply With Quote  
     

  12. #11  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
    Join Date
    Mar 2008
    Location
    Montreal
    Posts
    2,256
    Quote Originally Posted by Harold14370
    I guess nerd girl has turned in her homework by now.

    My answer is that the dissolved oxygen, whether it is heavy or regular oxygen, is continually depleted by plant respiration and decay of dead cells. This happens in both light and dark.

    The increase of oxygen-16 during daylight is due to photosynthesis. The new oxygen is coming from dissolved carbon dioxide, not the dissolved oxygen, and so it is the regular oxygen-16 isotope.
    Sounds like a perfect answer to me.
    Reply With Quote  
     

  13. #12  
    Forum Professor Zwirko's Avatar
    Join Date
    Sep 2008
    Location
    55 N, 3 W
    Posts
    1,082
    Just a quickie:

    The oxygen that is released from photosynthesis is derived from water (the so-called "water-splitting" reaction.
    Reply With Quote  
     

  14. #13  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
    Join Date
    Mar 2008
    Location
    Montreal
    Posts
    2,256
    Haha I should have caught that, egg on my face
    Reply With Quote  
     

  15. #14  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,822
    Thanks for the correction, guys. I knew CO2 was being used up, but it turns out that goes into making carbohydrates.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •