Methods of Transport

• What does it mean if a method of transport is Passive?


  That no cellular energy is required to move molecules
• What does it mean if a method of transportation is Active?


  It requires energy from respiration
• What type of transport is SIMPLE diffusion?


  Passive transport
• What type of molecules does simple diffusion transport?


  Small and non-polar molecules
• What is SIMPLE diffusion?


  When molecules move from high to low concentration, down the concentration gradient until equilibrium is reached.
• How is simple diffusion used in the cell membrane?


  To move small non-polar molecules between the phospholipid bi-layer.
• What type of transport is FACILITATED diffusion?


  Passive transport
• What type of molecules does facilitated diffusion transport?


  Polar/charged/hydrophilic/large molecules.
• What is FACILITATED diffusion?


  From high to low concentration until equilibrium reached

  When molecules pass through a channel protein

  Repelled by non-polar/ hydrophobic fatty acid tails
• Facilitated Diffusion - Gated


  A type of passive transport where molecules move through a channel or carrier protein, which can be gated to regulate the transport process
• What types of transport is OSMOSIS?


  Passive transport
• What type of molecule does osmosis transport?


  Water
• What is osmosis?


  Osmosis is the movement of water molecules from a solution of high water potential to a solution of lower water potential down the concentration gradient across a semi-permeable membrane.
• Water Potential


  The energy associated with water molecules due to their interactions with their surroundings.
• Osmotic pressure = The force exerted on a semi permeable membrane due to the movement of solvent across it
• What is required for the movement of molecules against the concentration gradient?

  Specific carrier proteins and energy in the form of ATP
• What is endocytosis and its types?


  • Bulk transport of large particles or fluids through the cell membrane
  • Types:
  • Phagocytosis: solid particles
  • Pinocytosis: small droplets of fluid
• What is exocytosis?


  Bulk transport of materials out of a cell
• How are proteins transported out of the cell during exocytosis?


  They are packaged into secretory vesicles that pinch off from the Golgi apparatus
• What is osmosis?


  The net movement of water molecules from higher to lower water potential
• What happens during osmosis until equilibrium is achieved?


  Net movement of water molecules occurs
• What is water potential?


  A measure of the ability of water molecules to move freely in solution
• How does the presence of solutes affect water potential?


  It decreases the water potential
• What is the Greek letter used to denote water potential?


  Psi (Ψ)
• What is the water potential of pure water?


  Zero
• What does isotonic mean?


  Solutions that have the same water potential
• What happens when cells are placed in a hypotonic solution?


  Water molecules move into the cell by osmosis
• What does hypertonic mean?


  A solution with a lower water potential compared to another
• What happens when cells are placed in a hypertonic solution?


  Water molecules move out of the cell by osmosis
• What does turgid describe in a cell?


  A cell that is full of water due to osmosis
• What is plasmolysis?


  Detachment of the plasma membrane from the cell wall due to water loss
• What is crenation?


  A state of animal cells that have shriveled due to water loss
• How do hypotonic, isotonic, and hypertonic solutions affect cell behavior?


  Hypotonic causes water influx, isotonic causes no net movement, hypertonic causes water efflux
• Osmosis and cell shape


  Osmosis can cause cell swelling (hypotonic), cell shrinkage (hypertonic), or cell bursting (severe swelling)
• Cell membrane role


  Selectively allows or prevents substances to enter or leave the cell, maintains cell shape and structure, communicates with the environment, and regulates cell growth and proliferation
• What happens in dilute solutions? (AC)

  Cells swells, may burst if pressure becomes too high for the membrane to withstand (no cell wall)

  HYPOtonic, high water potential
• What happens in a concentration solution? (AC)


  Water potential is lower or negative due to solute- HYERtonic.

  Cells lose water from cytoplasm and shrivel- CRENATED
• What happens to animal cells in a ISOTONIC solution?


  No net movement of water in or out of the cell
• What happens to cells in concentration solution (PC)?


  Vacuole shrinks and cytoplasm pulls membrane away from the cell wall as it shrinks- called plasmolysis
• What happens to cells in dilute solution? (PC)


  Cell swells and expands becoming turgid, cell contents push against cell wall

  Cell wall is strong so it withstands pressure without lysis