C.2.3 - cell transport

• Passive transport - cell doesn’t use extra energy

  • except kinetic molecular energy, which is in each atom
• Passive transport

  • Diffusion - high -> low concentration
• Concentration gradient - uneven distribution of concentration dictating direction of water/solute flow
• Speed of diffusion: gases > liquids > solids
• Factors of speed of diffusion

  • Temperature
  • SA:V  
  • Pressure
  • Concentration gradient
• Passive transport

  • Osmosis - diffusion in water through semi-permeable membrane
• Osmosis

  • Hypertonic - more solute outside of cell
  • "Plasmolysed"
  • shrinks
  • known as plasmolysis or crenation
• Osmosis

  • Isotonic
  • "Flaccid"
  • Equilibrium ≄ not moving, just no concentration gradient. Water is still moving, but rate at which it enters/leaves is the same. 
• Osmosis

  • Hypotonic - more solute inside cell
  • "Turgid"
  • Grow
  • Known as deplasmolysis or cytolysis
• Passive transport

  • Facilitated diffusion - diffusion through proteins in membrane
  • Carrier protein is like a door
  • specific molecule is like the key
• Active transport - low -> high concentration, needs ATP
• Active transport

  • Membrane pumps - used to build up a certain concentration of an ion (ex. Sodium, potassium) for nerve function
• Active transport

  • Endocytosis - membrane changes shape to enter cell
• Active transport

  • Exocytosis - membrane changes shape to exit cell
• Cell transport applications

  • Cancer treatment - finding cancer cell specific proteins