Cellular organelles 3 (MJC)

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Cellular organelles 3 (MJC)
2012-02-14 04:19:15
MJC cellular organelles

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  1. What is the function of the darkly-stained region shown in the micrograph above?
    It contains many copies of genes that codes for ribosomal RNA needed for the formation of ribosomes.

  2. The function of the organelle above is to _________________________________.
    Serve as a site for catabolic respiratory activity to synthesise Adenosine Triphosphate (ATP).

  3. What features of the organelle above suggest that it may come from a prokaryotic ancestor cell?
    The presence of circular DNA and 70S ribosomes.

  4. The organelle shown in the electron micrograph is found in abundance in liver cells. Suggest a reason for this observation.
    This is because one function of the smooth endoplasmic reticulum is to carry out detoxification reactions which occurs in liver cells.

  5. What is the function of the organelle above?
    To control all cellular activities like cell division and protein synthesis.

  6. What are the two features that distinguish between smooth and rough endoplasmic reticulum?
    • rER is granular due to the presence of ribosomes while sER is non-granular.
    • rER is more regular in shape while sER is tubular.

  7. Lysosomes that buds off the trans face of Golgi Apparatus contains _____________ which is important for destroying worn-out organelles and this process is called___________.
    Hydrolytic enzymes, autophagy

  8. _________, the process of adding carbohydrates to proteins occurs in the __________.
    Glycosylation , rough Endoplasmic reticulum

  9. State a function of the organelle shown above.
    Anchorage for cilia or flagella


    Organisation of spindle fibers during cell division

  10. State why the organelle above is finely granular.
    This is due to the presence of ribosomes in the mitochondrial matrix.

  11. What is the organelle shown above and describe its function.
    • It is a polysome and its function is to speed up protein synthesis
    • where it reads one strand of mRNA simultaneously, helping to synthesize the same protein at different spots on the mRNA.

  12. The granular appearence of the organelle above is due to the presence of ___________, which has a sedimentation coefficient of either _____ or _____.
    Ribosomes, 70S, 80S
  13. Lysosomes are bound by a single membrane. State the importance of this membrane.
    Lysosomes contain hydrolytic enzymes such as lipases and proteases. The membrane helps separate the contents of the lysosomes from the organelles of the cell, thus preventing the break down of the entire cell.
  14. State a safety mechanism that prevents the contents of lysosomes from initiating autolysis.
    The lysosomes contains hydrolytic enzymes which has an optimum pH of 4.5. The cytoplasm have a pH of 7.0 ~ 7.4 which denatures the hydrolytic enzymes if it is accidently released into the cell.
  15. The cell membrane is continuously being depleted due to pinocytosis and endocytosis. State how the cell membrane is replenished.
    Vesicles containing glycoproteins and glycolipids bud off from the endoplasmic reticulum and fuses with the cell membrane, hence replenishing it.