Facilitated diffusion

• What are the two types of diffusion mentioned?

  Simple and facilitated diffusion
• What is diffusion?

  Net movement from higher to lower concentration
• What happens to particles during diffusion?

  They move until evenly distributed
• What is the concentration gradient?

  Path from high to low concentration
• Is diffusion an active or passive process?

  It is a passive process
• What type of molecules can diffuse through cell membranes easily?

  Small, non-polar molecules
• Why can oxygen and carbon dioxide diffuse easily through cell membranes?

  They are small and non-polar
• What factors affect the rate of diffusion?

  • Concentration gradient
  • Thickness of exchange surface
  • Surface area
• How does the concentration gradient affect diffusion rate?

  The higher it is, the faster diffusion occurs
• What happens to diffusion as equilibrium is reached?

  Diffusion slows down over time
• What are microvilli?

  Projections that increase surface area
• How much can microvilli increase surface area?

  About 600 times
• What is facilitated diffusion?

  Diffusion through carrier or channel proteins
• What types of molecules typically undergo facilitated diffusion?

  Larger or charged molecules
• What are the two types of proteins involved in facilitated diffusion?

  Carrier proteins and channel proteins
• How do carrier proteins function?

  They change shape to move molecules
• What do channel proteins do?

  Form pores for charged particles to diffuse
• What factors affect the rate of facilitated diffusion?

  • Concentration gradient
  • Number of channel or carrier proteins
• What happens to the rate of facilitated diffusion as equilibrium is reached?

  It levels off
• How is glucose absorbed into red blood cells?

  Via GLUT 1 carrier proteins
• What are aquaporins?

  Channel proteins for water diffusion
• How do kidney cells utilize aquaporins?

  To reabsorb water efficiently
• How do you calculate the rate of diffusion from a graph?

  • For a straight line: find the gradient
  • For a curved graph: draw a tangent and find its gradient
• What is the formula for calculating the gradient of a line?

  Gradient = change in y / change in x
• What units are used for the rate of diffusion?

  Moles per second (Ms)
• What does a tangent represent on a curved graph?

  The rate of change at a specific point
• What does the graph show about glucose uptake?

  It is slower by simple diffusion
• How much water needs reabsorbing daily?

  About 180 liters
• What does "Ms" stand for in diffusion rates?

  Moles per second
• How do you find the units for the rate of diffusion from a graph?

  Divide y-axis units by x-axis units