cell transport

• What is diffusion?

  The net movement of particles from an area of higher concentration to an area of lower concentration.
• What are the three main factors that affect 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 from the blood into the lungs?

  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, maximizing the rate of diffusion of molecules.
• How is surface area to volume ratio calculated?

  • Surface Area = Number of Sides x (Side Length x Side Width)
  • Volume = Length x Width x Depth
  • Ratio = Surface Area:Volume
• 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 (animals)
  • Ventilation (animals)
• What is osmosis?

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

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

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

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

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

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

  Turgor pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall.
• What may happen when a plant cell is placed in a very hypertonic solution?

  Water moves out of the cell by osmosis, causing the vacuole and cytoplasm to decrease in size, and the cell membrane may pull away from the cell wall, causing the cell to become plasmolysed.
• What is active transport?

  The movement of molecules from a more dilute solution to a more concentrated solution against a concentration gradient, using energy from respiration.
• How do plant root hair cells use active transport?

  Root hair cells use active transport to take up mineral ions from a more dilute solution in soils, such as magnesium and nitrates.
• How is active transport used to absorb the products of digestion?

  Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood.