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UW Self Assessment Question *Spoiler*

Discussion in 'Step I' started by tfom08, May 26, 2008.

  1. tfom08

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    Can an 85 kD protein be degraded into a 65 kD protein and a 35 kD protein? I know that with ribosomes the subunit measurements are a sedimentation measurement so the numbers aren't additive, but are kDs like that as well? The question shows an electrophoresis with an 85 kD protein at 10 min turning into a 65 kD protein and a 35 kD protein and I didn't think it could be cleavage into two new peptides because the weights of the two new peptides were too high, but apparently it is.
     
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  3. medstu2006

    medstu2006 Senior Member
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    Seems like a typo. The protein fragments should add up to its original length.
     
  4. tfom08

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    That was my reasoning so I picked degradation even though the lines on the electrophoresis looked more like cleavage I thought 85 being split into 65 and 35 was impossible. Seems like kind of an obvious error if so though.
     
  5. medstu2006

    medstu2006 Senior Member
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    What was the question? i'm sure they provide explanations for the ans too.
     
  6. tfom08

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    It was basically just an electrophoresis and at 10 min there was just a thick bar at 85 kD. At 20 min, 1/2 thickness of the original bar at 85, 65, and 35. At 30 min, thick bar at 65 and 35. So the pattern looked like a protein that was being cleaved as it was produced. And then the question was what process is going on in this cell? Cleavage looked like the right choice except that 65 + 35 = 100. The explanation they give makes fine sense except that it ignores the fact of the parts being larger than the original protein. That's why I'm not sure if the kD numbers need to add up or not:confused:
     
  7. Hurricane95

    Hurricane95 Senior Member
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    I doubt it...the kd are just mass numbers...the actual weights of the proteins. They HAVE to add up, it's conservation of mass....must be a typo? :confused:
     

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