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Lipids, membrane and transportation (Membrane (properties (impermeable to…

- - - - fat
        
        derivative of fatty acid
      - oil
        
        derivative of fatty acid
      - fatty acid
        
        saturated
        
        all single bond
        
        animal fats, butter, lard
        
        unsaturated
        
        have a/some double/triple bond
        
        polyunsat.
        
        Omega 3,6
        
        monounsat.
        
        Omega 9
        
        triacylglycerol = 3 fatty acid+ glycerol
        
        length and degree of unsat. H-C chain affects solubility
        
        longer R-chain and more double bond low solubility in water
        
        higher # of unsat. low M.T.
    - - phospholipid
        
        polar gr. joined by phosphate gr.
        
        glycerophospholipid
        
        glycerol+2 fatty acids+ PO4+Alc.
        
        sphingolipid
        
        sphingosline+ fatty acid+ PO4+choline
        
        phospholipids may consist of various fatty acid
      - glycolipids
        
        lacking a phosphate gr., but containing a simple sugar or complex oligo sac at their polar end
        
        sphingolipid
        
        only one fatty acid chain linked to the N in sphinogosine and form amine bond
        
        sphinogomyelin
        
        found in membrane and classified as phospholipid
        
        galactolipid ( sulfolipids)
        
        predominant in plant cell
        
        in thylakoid memb. of chloroplast
        
        phosphate is often the limiting plant in soil
      - contains hydrophilic moieties
        
        -OH
      - archaebacterial ether lipids
        
        stable membrane structure that help archae survive in harsh condition
    - - sterol (steroid)
        
        tetracyclic ring structure
        
        important in maintainging cell membrane fluidity
        
        served as precursor of bioactive compound; streoid hormone
        
        act as detergent in intestine
      - phosphatidylinositol 4,5-bisphosphate
        
        in cytoplasmic face to plasma memb.
        
        served as reservoir of messenger molec.
- - - - micelle
        
        favored when the cross-sectional area of head group is greater than that of the acetyl chain
      - bilayer
        
        favored when the cross-sectional areas of the head group and the side chain are similar, such as glycerophospholipids and sphingolipids
      - vesicle
        
        is formed when a bilayer folds back on itself, generating a hallow shere
  - - - integral membrane proteins
        
        associated with membrane through hydrophobic interaction
        
        can be removed by detergents and denaturant
      - peripheral membrane protein
        
        associated with the membrane through electrostatic interaction and H-bond with the protein or polar head group of the lipid
        
        can be removed by carbonated and high pH
      - Amphitropic proteins
        
        found in both cytosol and in association with membranes
  - - - cholesterol is the key modulator of memb. fluidity
      - cholesterol's hydroxyyl group forms a H-bond with carbonyl oxygen atom of a phospholipid head group
- - - - simple difussion
        
        E required to remove the hydration shell and the energy activation for diffusion through bilayer
      - facilitated diffusion
        
        "protein transpoter" ; reduce Eact of transmembrane diffusion of the solute by providing an alternative path through the bilayer for specific solutes
  - - - ion gradients play important role in active transport and E conservation
    - - they are : gated" ; opened or closed in response to some cellular event
        
        ligand-gated channels: binding of small molecules trigger the opening or closing of the channels
        
        voltage-gated channels
        
        a change in transmembrane electrical potential causes a charged protein domain to move relative to the membrane
        
        3 types
        
        voltage-gated K+ channel
        
        voltage-gated Na+ channels
        
        voltage-gated Ca2+ channels
    - - the central of the channel is just wide enough for a single K+ to pass