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Proteins synthesized in a cell

  1. Mar 2, 2005 #1
    I have been asked to describe the pathway the following types of proteins follow and where they are synthesized in the cell.

    (a) Soluble proteins meant to remain in cytoplasm-

    Here wouldnt this follow the pathway cytoplasm-ER-golgi-exocytosis\

    (b) membrane proteins meant to remain in cell membrane

    this would follow cytoplam-ER-Golgi-plasma membrane

    (c) soluble proteins meant to be secreted in the cell

    this should follow same as (a)

    Now, im not sure if this is right or if i have adequatley described the pathway. Thanks. o:)
     
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  3. Mar 3, 2005 #2

    Moonbear

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    In (a), if they are supposed to remain in the cytoplasm, why would they be exocytosed? Check your definition of exocytosis.

    In (b), how are they getting from the golgi to the plasma membrane?

    For (c), check the wording of the question. Does it really say secreted in the cell, or does it say secreted from or by the cell?

    For all three:
    Why did you start with cytoplasm?
    Specify which type of ER.
    In which organelle is the actual synthesis occurring?

    Whether required for the assignment or not, be sure you can give a brief description of what is happening in each organelle where proteins are being processed.
     
  4. Mar 3, 2005 #3

    Actually, for C, it says secreted outisde the cell. Then I believe it would follow the same pathway, Cytoplasm-ER(synthesis of soluble proteins)-Golgi-(the packaging) and then from there sent to other parts of body. And for A, is it that it will stay in the cytoplasm where there are ribosomes that willk sythensize it. I am a bit confused
     
  5. Mar 3, 2005 #4

    Moonbear

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    You already have that proteins are synthesized in the ER, so does it make sense to you that would they start out in the cytoplasm if they haven't been synthesized yet?

    To be secreted outside the cell, after they've been packaged by the golgi, they are still inside the cell. How do they get out of the cell?

    If the protein is synthesized in the ER, why would it need to be synthesized again in the cytoplasm?

    However, you are right that ribosomes are involved in the synthesis, but at what step? Do you know the difference between smooth and rough ER?
     
  6. Mar 3, 2005 #5
    Yes I know that it is the rough endoplasmic reticulum that is involved in protein synthesis
     
  7. Mar 4, 2005 #6

    Moonbear

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    And do you know why it's called "rough"? In other words, what makes it look rough?
     
  8. Mar 4, 2005 #7
    The ribosomes are what make it look rough I believe
     
  9. Mar 4, 2005 #8

    Moonbear

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    Right. So when the protein is being synthesized in the ER, that's where and when the ribosomes are doing their job.
     
  10. Mar 4, 2005 #9
    So then all three instances would have to pass through the rough ER?
     
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