NEURO

    Cards (316)

    • Water
      • Oxygen is partially negative, and hydrogen is partially positive
      • These charges allow water to form hydrogen bonds
    • The density of ice is lower than water
    • Ions
      Charged substance
    • Ions
      • Carry signals in the body
      • Act as an energy store - secondary active transport
      • Interact biochemically with proteins and other molecules
    • Classes of ions
      • Physiologically useful ions
      • Biochemically useful ions
    • Calcium is both physiologically and biochemically useful
    • Ions in aqueous solution
      Opposite charges attract each other and form hydration shells
    • Smaller ions
      • Have bigger hydration shell
      • Have higher charge density
    • Hydration shell
      Affects mobility in solution, the effective size of the ion, and the interactions with proteins
    • Stokes law
      Ionic mobility is inversely proportional to its radius
    • Membranes
      Lipid bilayers
    • Lipid bilayers
      Amphipathic nature drives formation of bilayers they have hydrophobic heads, and hydrophilic tails
    • Biological membranes
      • Consist of a continuous double layer of lipid molecules
      • Membrane proteins are embedded in the lipid bilayer
      • Lipid bilayer is fluid, with individual lipid molecules able to diffuse rapidly within their own monolayer
      • Membrane lipid molecules are amphipathic
      • The most numerous are the phospholipids
    • Concentration of ions against gradient
      Requires energy
    • Cells get energy
      From the hydrolysis of ATP
    • Pumps
      Perform primary active transport
    • Pumps
      • Membrane proteins
      • Fairly slow
      • Nearly always move cations (e.g. calcium pump)
    • Sodium-potassium ATPase pump
      2K+ in and 3Na+ out
    • Symporter
      One ion
    • Antiporter or exchanger
      Two ions in opposite directions
    • Cotransporter
      Secondary active transport (e.g. sodium-calcium exchanger, 3Na+ in, 2 Ca2+ out)
    • Ion gradients
      • Represent a source of energy
      • Can be used to transmit information
      • Can be used to power cellular processes
    • Ion channels
      Transmembrane proteins
    • Sodium channels open
      Depolarisation
    • Potassium channel opens
      Hyperpolarisation
    • Sodium and potassium channels open
      Depolarisation
    • Chlorine channels open
      Hyperpolarisation
    • Calcium channels open
      Diverse
    • Cys loop receptors
      • Nicotinic AChR
      • GABAa
      • 5HT3 receptor
      • Inhibitory glycine receptor
    • Ach binding protein
      • Pentameric protein
      • N terminal extracellular domains if nicotinic receptor
      • Lost its transmembrane and intracellular domains
      • Used as a template for modelling other ligand gated ion channels
    • Cys-loop receptors
      An important superfamily of ligand-gated ion channels (LGICs)
    • Facilitated diffusion
      The process by which ions and molecules cross lipid bilayers with the help of specialized transport proteins
    • Ions cannot cross lipid bilayers by simple diffusion
    • Different concentrations between either side of the membrane causes a gradient
    • Facilitated diffusion
      1. Ions flow down gradient
      2. Until concentrations equal on both sides
      3. Equilibrium is set up
    • Molecules that punch holes in membranes

      Said to facilitate diffusion
    • Facilitated diffusion mechanisms
      • Pumps
      • Carriers
      • Proteins
      • Channels
    • 1D diffusion
      Movement along DNA
    • 2D diffusion

      Movement in a membrane
    • 3D diffusion

      Movement in liquid, cytosol, extracellular fluid
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