Microscopy, Cells, Organelles, Mitosis: Answers

#85 Spinal cord. Nissl stain

What is the rough endoplasmic reticulum and with what synthetic activity is it associated?
Membranous organelle with attached ribosomes, site of protein synthesis (for export). Why are the nucleus and the nucleolus not visible in some neurons? Organelles not in the plane of section.

#107 Pancreas. Guinea pig. Acid fuchsin-toluidine blue

What subcellular organelle is responsible for attracting the basic stain? Rough endoplasmic reticulum. How do you account for the acidophilia in the apical compartment?
The secretory granules contain zymogen granules with positively charged groups.

#103a Kidney, Guinea pig, PAS

What structures are seen with the electron microscope in these stained areas?
Glycocalyx at apex and basal lamina at base

Questions

  1. What are serial sections and why are they important?
    A continuous series of sections, which reveal structures in three dimensions.
  2. What is the relationship between heterochromatin and the synthetic activity of DNA?
    Heterochromatin is transcriptionally inactive DNA. A euchromatic nucleus is relatively unstained because the genetic material is being read.
  3. Where is the site of synthesis of ribosomal RNA?
    The nucleolus.
  4. What is the relationship of protein molecules to the lipid bilayer in the fluid mosaic model of the membrane?
    Integral membrane proteins move within the lipid bilayer.
  5. What is the function of mitochondrial cristae?
    Site of enzymes related to ATP production.
    What are cristae morphologically?
    Folds of inner mitochondrial membrane.
  6. What is the functional significance of the Golgi complex?
    Site of posttranslational modifications, packaging, and sorting of proteins.
  7. How many membranes comprise the nuclear envelope?
    Two. The wall of a mitochondrion? Two. The cisternae of the Golgi complex? One.
  8. What are the cytological and functional differences between cilia and microvilli?
    Cilia are motile microtubule based structures; microvilli are non-motile actin based structures.

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