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EK Biology In-Class Exam Lecture 1

Discussion in 'MCAT Study Question Q&A' started by futuredoctor10, Dec 30, 2008.

  1. futuredoctor10

    Classifieds Approved 10+ Year Member

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    Question.

    Passage: "Arsenate, a derivative of arsenic, is a deadly poison that acts as a substrate for glyceraldehyde 3-phosphate dehydrogenase."

    Question:
    The action of arsenate on glyceraldehyde 3-phosphate dehydrogenase is best described as:
    A. competitive inhibition
    B. noncompetitive inhibition
    C. allosteric inhibition
    D. negative feedback

    Based on the passage alone, you cannot distinguish if the inhibition is competitive or noncompetitive, correct?


    I think the way to answer this question is to look at the answer choices. D cannot be correct. According to EK, "You will not be asked to distinguish allosteric inhibition from noncompetitive inhibition on the MCAT." First off is this statement true?



    If so, then B and C are the same choice, and by process of elimination A must be correct.

    Does "substrate" imply a substrate at the active site and therefore competitive inhibition? Or do you call molecules that bind at places other than the active site (noncompetitive inhibitors) 'substrates' as well?
     
  2. TooMuchResearch

    TooMuchResearch i'm goin' to Kathmandu...
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    Substrates bind the active site. The answer is A.
     
  3. futuredoctor10

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    Thanks! So substrates bind the active site.
    Molecules that bind an allosteric site are called what?

    Also allosteric inhibition = noncompetitive inhibition for MCAT purposes right?
     
  4. G1SG2

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    Well, the term "substrate" can be used rather loosely...it can also refer to noncompetitive inhibition but I think your process of elimination worked well to answer the question. For allosteric regulation, the regulatory molecule is usually referred to as an activator (enhances the protein's activity) or inhibitor (represses its activity).
     
  5. futuredoctor10

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    Oh right, activators and inhibitors... thanks!
     

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