Cell Transport

Cards (24)

  • Diffusion
    The movement of particles from an area of high concentration to an area of low concentration. Particles move down a concentration gradient.
  • Why can we smell things which are far away?
  • Diffusion
    • Occurs in liquids and gases where molecules are constantly moving and bumping into each other, allowing them to spread out
    • Does not occur in solids where particles are tightly packed
  • As temperature increases
    Kinetic energy of particles increases, so they move around faster and diffusion is more rapid
  • Concentration gradient
    The difference in concentration between two areas
  • The larger the concentration gradient, the higher the rate of diffusion
  • Where diffusion occurs in living organisms
    • Animal cells
    • Plant cells
    • Unicellular organisms
  • Substances that diffuse in and out of an animal cell
    • Glucose (from food)
    • Oxygen (from lungs)
    • Carbon dioxide (excreted via lungs)
    • Urea from liver cells (excreted via kidneys)
  • Words that describe diffusion
    • Occurs in Solids
    • Movement of molecules from an area of lower to higher concentration
    • Passive process (doesn't require extra input of energy)
    • Movement is Random
    • Occurs in Fluids
    • Active process (requires extra input of energy)
    • Movement of molecules from an area of higher to lower concentration
  • Diffusion
    The movement of particles from an area of high concentration to an area of low concentration
  • As temperature increases
    Particles have higher kinetic energy
  • The higher the concentration gradient
    The higher the rate of diffusion
  • Every organism, whatever its size, needs to exchange materials with the environment
  • Surface area to volume ratio (SA:V ratio)

    How easy the exchange of substances is, depends on the organism's surface area to volume ratio
  • An ant has a much larger surface area to volume ratio than an elephant
  • As the size of an organism gets bigger
    The surface area to volume ratio (SA:V) gets smaller
  • Large organisms, like humans, cannot absorb enough oxygen through our skin surface, so we need efficient gas exchange surfaces such as lungs
  • Features of a good gas exchange system
    • Folded shape - large surface area
    • Thin - to provide a short diffusion pathway
    • Efficient blood supply - to maintain a high concentration gradient
    • Ventilation - ensuring there is always lots of oxygen to maintain a high concentration gradient
  • A good blood supply in the lungs and small intestine
    Maintains a high concentration gradient, which increases the rate of diffusion
  • Features of a good gas exchange system
    • Non-flat shape - increases surface area
    • Thin - reduces diffusion distance
    • Good blood supply - maintains high concentration gradient
    • Ventilation - maintains high concentration gradient
  • Soil has a lower concentration of mineral ions than root hair cells
  • Root hair cells need to use active transport to move mineral ions from an area of lower to higher concentration
  • Active transport
    Using energy to move molecules against a concentration gradient with the help of a transport protein
  • Organisms use active transport when molecules need to move from low to high concentration