1. SDN Mobile is now free on iTunes and on the Google Play Store. Enjoy!
    Dismiss Notice
  2. This forum is for support and discussion only. Please promote test prep materials/services (including AMAs) in the Special Offers subforum only. Thanks!
    Dismiss Notice
Dismiss Notice

Interview Feedback: Visit Interview Feedback to view and submit interview information.

Interviewing Masterclass: Free masterclass on interviewing from SDN and Medical College of Georgia

Biology Subject Test 1 Item 34

Discussion in 'MCAT Study Question Q&A' started by Simran1031, Dec 30, 2008.

  1. Simran1031

    Simran1031 Princess of 2014=)
    2+ Year Member

    Joined:
    Jul 6, 2007
    Messages:
    463
    Likes Received:
    0
    MDApps:
    Status:
    Pre-Medical
    Hey guys,
    this type of question always gives me a hard time.. i was wondering if someone could explain this to me.
    Item 34 Kaplan bio subject test

    if a 18O-labeled glucose given to a rat, where will the label appear?
    a. exhaled co2
    b. plasma h20
    c. exhaled h20
    d. intracellular h20.
    the answer is a. the explanation talks about glycolysis and how o2 is the final oxygen acceptor and is the one that comes out during expiration..but im confused..:confused:
     
  2. futuredoctor10

    Verified Account 10+ Year Member

    Joined:
    Jan 25, 2007
    Messages:
    1,658
    Likes Received:
    15
    Status:
    Resident [Any Field]
    Good question! I am not sure... the glucose subject to aerobic respiration (gluc + 02) will produce CO2 and H20 but I dont know how you know that the labeled glucose ultimately becomes exhaled CO2
     
  3. OP
    OP
    Simran1031

    Simran1031 Princess of 2014=)
    2+ Year Member

    Joined:
    Jul 6, 2007
    Messages:
    463
    Likes Received:
    0
    MDApps:
    Status:
    Pre-Medical
    :confused:yea..this type of question has historically tripped me up..
     
  4. G1SG2

    5+ Year Member

    Joined:
    May 2, 2008
    Messages:
    1,463
    Likes Received:
    2
    Status:
    Pre-Medical
    Whenever I see glucose in a Bio passage, I usually think of the combustion of glucose with oxygen/aerobic respiration. Doing so would make answer choice a (exhaled co2) seem appropriate, as then one would think of TCA.
     
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  5. futuredoctor10

    Verified Account 10+ Year Member

    Joined:
    Jan 25, 2007
    Messages:
    1,658
    Likes Received:
    15
    Status:
    Resident [Any Field]
    so to answer this question... is my reasoning right?
    Glucose labeled in a rat would undergo aerobic respiration.

    Glucose + O2 --> CO2 + H20

    Exhaled CO2 contains the labeled "oxygen" from the glucose, because in the TCA cycle (aka Krebs cycle) the carbon dioxide molecules are "products" of the intermediate reactions of the cycle?
     
  6. G1SG2

    5+ Year Member

    Joined:
    May 2, 2008
    Messages:
    1,463
    Likes Received:
    2
    Status:
    Pre-Medical
    Seems correct. The labeled glucose in glycolysis probably yielded two labeled pyruvates, and then led to the byproduct CO2, which carried the label.
     
    Stop hovering to collapse... Click to collapse... Hover to expand... Click to expand...
  7. rnicholsaz

    2+ Year Member

    Joined:
    Dec 30, 2008
    Messages:
    14
    Likes Received:
    0
    The end result of glucose in oxidative conditions is CO2 and water. The CO2 is released in the Krebs cycle. The water is produced by O2 being the final electron receptor in oxidative phosphorylation, but doesn't use any of the original glucose molecule to make water.
     
  8. futuredoctor10

    Verified Account 10+ Year Member

    Joined:
    Jan 25, 2007
    Messages:
    1,658
    Likes Received:
    15
    Status:
    Resident [Any Field]
    Thanks pookiez88 and rnicholsaz - that makes a lot of sense and helped clarify the question completely!
     
  9. OP
    OP
    Simran1031

    Simran1031 Princess of 2014=)
    2+ Year Member

    Joined:
    Jul 6, 2007
    Messages:
    463
    Likes Received:
    0
    MDApps:
    Status:
    Pre-Medical
    thanks for responding everyone!
     

Share This Page