Cells and cell membranes 1

• Cell


  A functional unit of organisms to maintain homeostasis
• The seven characteristics of life

  • Metabolism
  • Growth
  • Reproduction
  • Irritability
  • Adaptation
  • Movement
  • Cells
• Cell


  • ~ 100 trillion cells make up the typical human
  • Some cells have ability to reproduce additional cells
  • Basic commonalities of the cells:
  • Oxidation of nutrients to release energy
  • Nutrient consumption and energy production
• Cytoplasm


  A thick solution that fills each cell and is enclosed by the cell membrane
• Mitochondrion


  An organelle that performs oxidative phosphorylation generators and generates ATP
• Nucleus


  An organelle that stores the cell's DNA and therefore controls all of cell's activities (e.g. growth and metabolism)
• Ribosomes


  The protein factories of the cell
• Endoplasmic reticulum


  A system of membranous organelles that shares part of its membrane with that of the nucleus
• Lysosome


  A membrane-bound cell organelle that contains digestive enzymes
• Golgi apparatus


  A membrane-bound organelle that is made up of a series of flattened, stacked pouches called cisternae
• Fluid mosaic model of cell membrane

  Describes the cell membrane as a two-dimensional liquid that restricts the lateral diffusion of membrane components
• Seymour J. Singer


  (1924 - 2017)
• Garth L. Nicolson


  (1943 age 77)
• Structure of the cellular membranes

  • Lipid bilayer (~43%)
  • Proteins (globules/fibres; surface/integral) (~49%)
  • Carbohydrate – glycocalyx (glycoproteins/glycolipids) (~8%)
• Functions of the Cell Membrane

  • Mechanical or Structural function
  • Filter (Selective Permeability)
  • Active Transport (pumps)
  • Bulk Transport (Exocytosis and Endocytosis)
  • Markers & Signalling (Receptors)
  • Metabolic Activities
  • Passive Transport (ion channels and transporters)
• Electron


  (e-) is a subatomic particle, with a negative elementary electric charge
• Anion


  (Greek ἄνω - "up"), is an ion with more electrons than protons
• Cation


  (Greek κάτω - "down"), is an ion with fewer electrons than protons
• Anode


  Reduction electron gain
• Cathode


  Oxidation electron loss
• Electrolyte


  Carriers of current
• Electrical conductivity in metal crystals

  Electrical conductivity in electrolyte
• Electrochemical gradient


  Driving force for transmembrane transport
• Chemical driving force


  Concentration gradient across the membrane
• Electrical driving force


  Charges difference across the membrane
• Electric model of Cell Membrane

  If cell membrane is capacitor-resistor complex, then the cells are batteries
• Membrane potential (Vm)


  Varies from -80 to -20 mV (depending on the cell type)
• Walther Hermann Nernst


  (1864 – 1941), Nobel Prize in Chemistry (1920)
• Nernst Equation


  E_ion = (RT/zF) ln([ion]_o/[ion]_i)
• Ions Contributing to Membrane Potential

  • K+
  • Cl-
  • Na+
  • Ca2+
• Alan Lloyd Hodgkin


  (1914 - 1998)
• Bernard Katz


  (1911 - 2003)
• David Goldman


  (1910 - 1998)
• Point out the factors which determine the value of membrane potential