Transport

• Simple Diffusion is the net movement from high to low concentration gradient until equilibrium
• Kinetic Energy is involved in simple diffusion
• Simple Diffusion molecules must be lipid soluble and small, not polar
• Facilitated Diffusion is a passive process where a protein transports a molecule across a membrane down a concentration gradient
• Osmosis is the movement of water from high to low water potential
• Pure Water = 0
• Isotonic Water Potential is an equilibrium between the cell and the environment
• Hypotonic Water Potential is when the cell is lower than the environment
• Hypertonic Water Potential is higher in the cell than the external environment
• Active Transport is the movement of molecules against the concentration gradient from low to high using metabolic energy and a carrier protein + ATP
• Active Transport Process

  • Molecules bind to complementary receptors
  • ATP binds and hydrolyses via ATP hydrolase
  • Carrier Protein changes shape and releases molecule
  • Phosphate ion is released and shape returns to normal
• Co-Transport is the movement of two or more substances in the same direction
• Co-Transport of Glucose and Sodium in the Ileum needs a higher concentration of sodium in the lumen but is usually higher in the epithelial cell
• In Co-Transport, sodium ions use active transport out of epithelial cell into blood, reducing Na+ concentration
• Na+ in the ileum binds to carrier protein with glucose, going against the concentration gradient, into the epithelial cell
• Glucose moves out of the epithelial cell via facilitated diffusion into the blood, down the concentration gradient