The movement of molecules across a membrane

• What are the types of diffusion?

  Simple diffusion: The movement of small, non-charged molecules directly across a plasma membrane moving down the concentration gradient.

  Facilitated diffusion: movement of large or charged molecules from high to low concentration through a channel protein.

  
• What factors affect Simple Diffusion?

  Concentration gradeiant

  Temperature

  Surface area

  Diffusion distance.
• What factors affect facilitated diffusion?

  Concentration gradient

  Temperature

  Channel size

  Number of channels available
• What is Active transport?

  The movement of large or charged molecules from a low to high concentration gradient through a carrier protein (requires energy in the form of ATP).

  
• What factors affect active transport?

  Amount of carriers

  Availability of energy
• What is Bulk transport?

  The transport of large or many substances across a cell membrane. Endocytosis refers to the bulk transport of material into the cell. Exocytosis refers to the bulk transport of material out of the cell.
• What is water potential?

  Water potential is the tendency of water molecules in a system to move. (Measures in Kilopascals, denoted ψ)
• What has the highest water potential?

  Pure water has the highest water potential and has a value of 0Kpa. SOlutions have a lower water potential than pure water and have a negative water potential.
• What is Osmosis?

  The movement of water molecules through a partially preamble membrane from a solution of high water potential to a solution of lower water potential.