1.3

• 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 substances are transported by diffusion in the lungs?

  Oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood.
• What substance is transported by diffusion in the kidney?

  Urea diffuses from cells into blood plasma.
• How are single-celled organisms adapted for diffusion?

  They have a large surface area to volume ratio, maximizing the rate of diffusion.
• 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.
• How do plant leaves and stems remain rigid?

  Turgor pressure from water moving in by osmosis causes the vacuole to swell and the cytoplasm to press against the cell wall.
• 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.
• 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.