RESULTS of MICROSCOPY...  Investigations of Cells - some major EUKARYOTIC ORGANELLES
                      electron microscopy has used fixed sectioned cells which are static (mcb9.5a*)
                      to describe organelles, mostly by presence or absence of membranes...


  
Single Membrane Bound (DIGESTIVE) Organelles:

  
1. endosomes... membrane bound vesicles of extra-cellular milieu internalized by ENDOCYTOSIS
        a.  endocytosis - cathrin protein "coated" membrane pits - pinch off endosome vesicles
        b. phagocytosis - whole cells engulfed & passed to lysosomes for digestion
        c. autophagy - worn-out organelles fuse with lysosome   mcb9.2a &  endosomes & lysosomes*

2. lysosomes... hundreds single membrane bound vesicles* (exclusive to animals- plants use vacuoles)
        have acid pH environment to help denature proteins (H⁺ATPases* & Cl transporters --> HCl)
        contains hydrolytic enzymes (nucleases, proteases, phosphatases, glycosylases) for digestion.
                         Tay-Sachs (tt): defective lysosomal enzyme which degrades ganglosides,
                                                glysolipids buildup in neurons ≈ dementia, blindness, and death
        nuclear & some cytosolic proteins aren't digested within lysosomes, but rather proteasome*
    
 

 
 
  Other Single Membrane digestive-like Organelles:
  
  3. plant vacuole...  membrane limited interior space (up to 80% cell volume) containing
            membrane transport proteins accumulate ions, nutrients, & wastes.                 mcb9.7*
            lumen holds digestive enzymes (has acid pH optima - acts like lysosomes).
            tonoplast membrane permeable to water influx, helps establish turgor pressure (5-20 ATM)


  4. peroxisomes... spherical (0.2-1.0 µm) organelle containing oxidases (catalase) that use O₂
                           to oxidize (remove e^-'s from) molecules as H₂O₂ (& other toxins).  mcb9.4*
           degrades FA's to acetyl groups - used to make cholesterols (esp. impt in liver/kidney cells).
                                  X-linked adrenoleukodystrophy (ADL): no FA digestion occurs,
                                  leads to several neuro-linked defects and death.                 
                                                                                                            
           plants contain glyoxysomes which oxidize stored lipids (very similar to peroxisomes).
  

    

 
  Membrane Complexes...   as Organelles: 

  5. endoplasmic reticulum... network of closed-flattened membrane sacks called cisternae
         found in all nucleated cells; involved in protein/lipid biosynthesis
         2 types:  SER (smooth) - lacks ribosomes                                                       mcb9.5
                                            - makes FA & phospholipds (esp. in hepatocytes)
                                            - detoxifies hydrophobic chemicals including carcinogens & pesticides
                        RER (rough)  - membranes bound with ribosomes                              mcb9.4*
                                            - makes plasma membrane proteins & exportable proteins of ECM
                                            - abundant in cells making  -  antibody proteins (plasma cells)
                                                                                    - pancreas (digestive enzymes & hormones)

 6. Golgi Complex... series flattened membrane sacks (cisternae) that take up ER transport vesicles
         and process contents via glycosylation (addition of carbohydrate residues).
         3 divisions:  cis - where ER vesicles enter                                                       mcb9.5b*
                           medial - where modifications (glycosylations) occur
                           trans - vesicle packages & budded off here for secretion               mcb9.6* 
 
 
 

 
 Double Membrane Bound Organelles:
  
 7. nucleus...  largest; double membrane bound - outer membrane contiguous with ER
         synthesizes DNA, rRNA, tRNA, primary transcript (mRNA preccursor)    
         peri-nuclear space (2-5nm) is contiguous with lumen of ER                  nucleus em*
         pores of protein nucleoporins (mcb 8.20a*) regulates nucleoplasm-cytoplasm exchange
                      via NLS* of 7 aa sequence @ C-terminus (N-pro-pro-lys-lys-lys-arg-lys-val-C)
         nucleolus - regions of rDNA that makes rRNA (but, ribsosomal proteins made in cytoplasm)
         nucleoplasm - 'cytoplasm' of the nucleus
            heterochromatin - condensed (darker EM color) = inactive DNA -                 mcb6.33a*
            euchromatin - non-condensed (lighter EM color) = active DNA
            lamins - fibrous proteins adjacent to inner nuclear membrane = frame for nuclear shape
  
 8. mitochondria... conducts ATP production of cell via oxidative metabolism of glucose & fatty acids
      outer membrane (50:50 lipid/protein) contains porin (mcb10.18*) transports most ligands < 10K
      inner membrane (25:75 lipid/protein) strictly regulates most transport into mitoplasm
      cristae - infoldings of inner membrane (mcb9.8* &  mcb12.6*    pic1* & pic2*)       
    

  
 9. chloroplast... largest green plant cell organelle (0.5-2.0 µm by 10 µm)
      has double membrane with extensive inner membrane-limited sacks called thylakoids (mcb9.9*)
      absorbs light energy via chlorophyllous pigments & makes ATP & NADPH (chemiosmosis)
      reduces CO₂ into CH₂O
          Similarities of Mitochondria & chloroplasts...
             1.  make ATP/NAD(P)H via similar mechanisms
                      - chemiosmosis: oxidative creation of H+ gradient coupled to ATP synthase
             2.  show mobility throughout cell
             3. divide by fission independent of whole cell's division
             4. autonomously replicate their own DNA [mito: 16,569 nucleotide pairs: about 37 genes]
                                 [chlp: 10fg or 120 genes - highly supercoiled & repetitive-up to 6 copies]
             5. both contain 70s - bacterial size ribosomes  [eukaryotes have 80s ribosomes]
             6. synthesize their own proteins on their own protein synthesizing machinery 

                "The Inner Life of a Cell " - a movie animation by John Liebler & Harvard U.
                         ►  REVIEW: major organelles of animal & plant cells
                      mcb5.19*(ans) & mcb5.19*(ans) - Quick Review of Major Eukaryotic Cell Organelles

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   Where do we get homogenous cell populations for microscopy?  

Cell Culture- growing isolated cells in defined media   single cells in controlled conditions... form colonies (clones)   req: 370C, pH, salts, essential amino acids, vitamins,   glucose, serum (growth factors - insulin & transferrin [Fe])      mcb6.36* & mcb22.3*      American Type Culture Collection   Society for in vitro Biology & Plant Tissue Culture
Single Cell Analysis...   Cytometer - instruments for analyzing cells and   Sorting Cells* - via fluorescent tags &  core facility         Microspectroscopy... a technique for           measurements of spectral absorption of stained          microscopic material in cells.   microspec apparatus