BIOMEMBRANES

BIOMEMBRANES

CYTOSKELETON
1. Microfilaments
  1. 8–9 nm in diameter
  2. made of monomeric actin subunits
  3. Membrane–microfilament binding proteins tack the actin cytoskeleton framework to
    1. membrane
2. Intermediate filaments
  1. 10-nm-diameter
  2. made of lamin subunits and other tissue- specific proteins
  3. adapter proteins attach them to
    1. desmosomes and hemidesmosomes
3. Microtubules
  1. 24 nm in diameter
  2. they are hollow tubelike structures
  3. made of alpha and beta tubulin subunits
  4. radiate out
    1. single microtubule-organizing center
4. funcitions in animal and plan cells
  1. contributes to cell movement
  2. cell polarity
  3. It organizes the contents of the cell
  4. Support for nuclear membrane
5. functions in bacteria
  1. controls cell length, width,andthe site of cell division
ORGANELLES OF THE EUKARYOTIC CELL
1. TWO BILAYER MEMBRANES
  1. THE NUCLEUS
    1. Houses the genome of the cell
    2. numerous nuclear pores: materials pass between the nucleus and the cytosol
  2. MITOCHONDRIA
    1. has highly permeable outer membrane protein-enriched inner membrane
    2. ATP synthesis : Enzymes in the inner mitochondrial membrane and central matrix
  3. CHLOROPLASTS
    1. thylakoid membranes in their interiors: contain the pigments and enzymes that absorb light— ATP syntesis
2. A SINGLE MEMBRANE
  1. The Golgi Complex
    1. processes and sorts secreted and membrane Proteins -it has three regions: the cis, the medial, and the trans.
  2. Plant Vacuoles
    1. Store Small water, ions, and nutrients -contain degradative enzymes and -has an acidic pH
  3. The Rough Endoplasmic Reticulum
    1. synthesizes
      1. membrane and organelle proteins
      2. all proteins to be secreted from the cell
  4. ENDOSOMES
    1. Take up plasma-membrane proteins and soluble materials from the extracellular medium and recycles or degrades them.
  5. LYSOSOMES
    1. Contain hydrolases - degrade unneeded cellular components and some ingested materials
  6. Peroxisomes
    1. Contain enzymes that oxidize various organic compounds without the production of ATP
  7. The Smooth Endoplasmic Reticulum
    1. synthesizes fatty acids and phospholipids
    2. detoxifies of hydrophobic chemical
Purification of cells and their parts:
1. Studies on cell structure require particular type or subcellular organelle from a cell
  1. Tissues contain mixture of cell types
  2. Cells filled with different organelles
2. Techniques for separating different cell types and organelles
  1. Flow Cytometry
    1. Separates Different Cell Types
    2. Can identify different cells on the basis of the light
      1. These can be by
        Scatter
        Fluorescence that they emit
        Fluorescence-activates cell sorter (FACTS)
        Separating different types of cells
  2. Disruption of Cells
    1. Releases Their Organelles and Other Contents by
      1. Vigorous homogenization
      2. Other techniques
      3. Sonication
    2. Swelling of cells
      1. Hypotonic solution
        Weakens the plasma membrane
        Easier rupture
  3. Centrifugation
    1. Yields fractions
      1. Of: partly purified organelles
        Differ in
        mass
        density
    2. Can Separate Many Types of Organelles
  4. proteins
    1. Transmembrane proteins
      1. Selectively solubilized
        Purified with nonionic detergents
  5. Organelle Specific Antibodies
    1. Using antibodies against organelle specific membrane proteins
      1. Useful in preparing
        Highly Purified Organelles
        Vesicles of similar
        sizes
        densities

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	Criado por luis roberto zacarias vidal mais de 8 anos atrás