Biology- Transport in Cells

    Cards (17)

    • Diffusion
      The net movement of particles from an area of higher concentration to an area of lower concentration
    • 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
    • Substances transported by diffusion in the lungs and the kidney
      • Lungs: oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood, both down their concentration gradient
      • Kidney: urea diffuses from cells into blood plasma so it can be excreted in urine
    • Single-celled organisms adapted for diffusion
      • They have a large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organism's needs
    • Calculating surface area to volume ratio
      1. Surface Area = Number of Sides x (Side Length x Side Width)
      2. Volume = Length x Width x Depth
      3. Ratio = Surface Area:Volume
    • Factors increasing the effectiveness of a gas exchange surface
      • Large surface area
      • Thin membrane (short diffusion path)
      • Efficient blood supply (animals)
      • Ventilation (animals)
    • Osmosis
      The movement of water from a dilute solution to a concentrated solution through a partially permeable membrane
    • Isotonic solution
      The concentrations of the external and internal (inside cell) solutions are the same
    • Hypertonic solution

      The concentration of the external solution is higher than that of the internal solution (inside cell)
    • Hypotonic solution
      The concentration of the external solution is lower than that of internal solution (inside cell)
    • Animal cell placed in very hypotonic solution

      Water moves into the cell, causing it to burst
    • Animal cell placed in very hypertonic solution

      Water moves out of the cell, causing it to shrivel up
    • Turgor pressure
      Water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall
    • Plant cell placed in very hypertonic solution

      Water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size. The cell membrane may pull away from the cell wall, causing the cell to become plasmolysed
    • 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 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. Ions such as magnesium and nitrates are required for healthy growth
    • How active transport is 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. Glucose is then transported to the tissues where it can be used in respiration