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THE CELL (cells (2 types (PROKARYOTIC (= before nucleus, lack membrane…

- - - - = before nucleus
      - lack membrane bound nucleus ( :red_cross: nuclear envelope )
      - small
      - few internal structures ( :red_cross: membranous organelle )
      - :check: cell wall outside plasmalemma
      - :red_cross: histones (specific basic proteins bound to DNA)
      - eg . bacteria
    - - = true nucleus
      - larger
      - :check: distinct nucleus surrounded by nuclear envelope
      - many membrane-bound organelles
      - DNA complex with histones
      - eg. protozoa , fungi , multicellular plants , animals
- - - - lipids ( phospholipids & cholesterols )
      - protein
      - oligosaccharides
    - - 3-layered structure = unit membrane
      - outer , electron-dense layer = outer leaflet
      - inner , electron-dense layer = inner leaflet
      - intermediate , electron-lucent layer
      - after fixation in osmium tetroxide
    - - phospholipids & associated proteins -fluid-mosaic model
      - phospholipids
        
        2 long , non-polar hydrocarbon chains ( hydrophobic tail )
        
        charged head group , polar ( hydrophilic head ) :
        
        form bilayer
      - proteins
        
        integral / transmembrane ( between)
        
        peripheral ( on surface )
      - sugar chain + protein = glycoprotein
        sugar chain + lipid(head) = glycolipid
    - - maintain structural integrity of cell
      - control substances movement
      - regulate cell-cell interactions
      - recognition - receptors , antigens , etc.
      - interface between cytoplasm & external milieu
      - establish transport systems for specific molecules
      - transducing extracellular physical & chemical signs intro intracellular events
  - - - organelles
        
        :check: all eukaryotes
        
        limiting membrane
        
        enzymes for cellular metabolism
        
        permanent components
        
        examples
        
        nucleus : DNA
        
        mitochondria : energy
        
        ER : proteins + lipids biosynthesis
        
        GA : biosynthetic products processing
        
        lysosome : digestion
        
        peroxisomes : fatty acid metabolism
      - cytoplasmic inclusions
        
        temporary components of certain cells
        
        accumulations of pigments , lipids , proteins , carbohydrates
        
        may / may not be enclosed in a membrane
      - cytoskeletons
        
        :red_cross: enclosed in membrane
        
        :red_cross: participate directly in cellular metabolism
        
        dynamic supportive framework within cytoplasm
        
        eg . centriole , microtubule , microfilaments , intermediate filaments
  - - - chromatin - genetic material
        
        complex of DNA & proteins
        
        basophilia characteristic of nucleus
        
        2 types ( degree of chromatin condensation )
        
        heterochromatin ( tightly packed DNA )
        
        euchromatin ( loosely packed chromatin , most active )
        
        light nuclei cells more active than condensed dark nuclei cells
        
        light stain areas
        
        DNA unfolded
        
        euchromatin --> active transcription
        
        basophilic area lightly stained
        
        dense stain areas
        
        heterochromatin --> inactive transcription
        
        adjacent nuclear membrane
        
        basophilic clumps under LM
        
        coiled strands of DNA bound to basic proteins (histones)
      - nucleolus - RNA synthesis center
        
        spherical structure - usually basophilic with H&E stain
        
        rich in rRNA & protein
        
        rRNA syntesis site & initial ribosomal assembly
        
        packaged with proteins to form ribosomal subunits
        
        enter cytosol via pores in nuclear membrane
      - nucleoplasm - macromolecules & nucleus particles for cell maintenance
        
        component that fills space between chromatin & nucleoli in nucleus
        
        proteins , metabolites & ions
        
        fibrous lamina is part of nuclear matrix
      - nuclear envelope
        
        2 parallel unit membranes with a perinuclear cisterna space in between
        
        nuclear pores formed at sites where inner & outer membranes fuse ( allow ribosomes & large molecules to pass between nuclues & cytosol )
        
        pore complex at nuclear pore - allows bidirectional nucleocytoplasmic transport
        
        polyribosomes associated with outer membrane
        
        continuous with cisternal space of rER
        
        fibrous lamina - closely associated with internal membrane
        
        helps stabilize nuclear envelope
        
        chromosomes associated with fibrous lamina
      - nuclear skeleton
- - - - protein synthesis
      - sac-like + parallel stacks of flattened cistarnae
      - ribosomes & polyribosomes on cytoplasmic surface
      - basophilic staining properties
      - functions
        
        segregate proteins for export
        
        glycosylation of glycoproteins
        
        phospholipid synthesis
        
        multichain proteins assembly
        
        post-translational modifications of new polypeptides
        
        abundant in hepatocytes ( liver )
    - - lack ribosomes
      - cisternae more tubular
      - continuous with rER
      - functions
        
        synthesize steroid hormones
        
        oxidation , conjugation , methylation process
        
        phospholipids synthesis for cell membrane
        
        skeletal & cardiac muscles sarcoplasmic reticulum
        
        abundant in liver cells & gonad cells
  - - - mitochondrial deficiency/dysfunction diseases - characterized by muscular dysfunction
        
        parkinson's , autism , mitchondrial disease , muscular dystrophy , lou gehrig's , chronic fatigue , huntington's , alzheimer's