Transport in Cells

• What is diffusion?

  The net movement of particles from high to low concentration
• What are the three main factors affecting the rate of diffusion?

  • Concentration gradient: larger gradient, faster diffusion
  • Temperature: higher temperature, faster diffusion
  • Surface area: larger surface area, faster diffusion
• What substance diffuses into the blood from the lungs?

  Oxygen
• What substance diffuses into the lungs from the blood?

  Carbon dioxide
• What substance diffuses from cells into blood plasma in the kidneys?

  Urea
• How are single-celled organisms adapted for diffusion?

  They have a large surface area to volume ratio
• How is surface area to volume ratio calculated?

  Surface Area = Number of Sides x (Side Length x Side Width)
• What is the formula for volume?

  Volume = Length x Width x Depth
• What are the four factors that increase the effectiveness of a gas exchange surface?

  • Large surface area
  • Thin membrane (short diffusion path)
  • Efficient blood supply (in animals)
  • Ventilation (in animals)
• What is osmosis?

  The movement of water from dilute to concentrated solution
• What does it mean when a solution is isotonic to a cell?

  The concentrations of external and internal solutions are the same
• What does it mean when a solution is hypertonic to a cell?

  The external solution is higher in concentration than the internal solution
• What does it mean when a solution is hypotonic to a cell?

  The external solution is lower in concentration than the internal solution
• What may happen when an animal cell is placed in a hypotonic solution?

  Water moves in, causing the cell to burst
• What may happen when an animal cell is placed in a hypertonic solution?

  Water moves out, causing the cell to shrivel
• How do plant leaves and stems remain rigid?

  Through turgor pressure from water moving in
• What may happen when a plant cell is placed in a hypertonic solution?

  Water moves out, causing plasmolysis
• What is active transport?

  The movement of molecules against a concentration gradient using energy
• How do plant root hair cells use active transport?

  To take up mineral ions from dilute soil solutions
• How is active transport used to absorb the products of digestion?

  To transport glucose from gut to blood