diffusion and active transport

Cards (27)

  • diffusion

    The movement of particles from an area of high concentration to an area of low concentration until they're evenly spread out, (for particles move randomly and spreads out).
    • Diffusion occurs in both liquids and gases because particles in these states have the FREEDOM TO MOVE randomly.
  • Here are some examples of Diffusion in CELLS:
    • oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves.
    • urea diffuses from cells into the blood plasma for excretion by the kidney.
    • digested food molecules from the small intestine diffuse into the blood.
  • You can increase the rate of diffusion by:
    • Increasing the difference in concentration between the two areas.
    • Increasing the TEMPERATURE, as particles have more energy to move faster.
    • Increasing the SURFACE AREA of the membrane where diffusion is occurring
  • The efficiency of exchange surfaces by diffusion is determined by the SURFACE AREA to VOLUME RATIO (SA:V).
  • LARGER organisms have a SMALLER SA:V ratio than smaller organisms.
  • Therefore the bigger cube has a lower surface area to volume ratio.
    A) 1m
    B) 6m
    C) 6:1
    D) 8m
    E) 24m
    F) 3:1
  • Gas Exchange in the Lungs
    In the lungs, it has tiny air sacs called alveoli which are surrounds by a capillary network.
    oxygen diffuses from the alveoli into the blood, while carbon dioxide moves from the blood into the alveoli to be exhaled.
  • Gas Exchange in the Lungs
    Adaptations of Alveoli for Gas Exchange
    • Has a HUGE SURFACE AREA to increase efficiency of gas exchange.
    • Has a MOIST LINING for dissolving gases, which aids in the diffusion process.
    • Their WALLS are THIN to minimize the distance gases must diffuse.
    • Surrounded by a crowded CAPILLARY NETWORK, for a rich blood supply and rapid gas exchange.
  • Gas Exchange in Plant Leaves
    Structure of Leaves
    • CARBON DIOXIDE diffuses into AIR SPACES within the leaf for photosynthesis.
    • Leaves have an EXCHANGE SURFACES underneath, with small openings called STOMATA.
    • OXYGEN and WATER VAPOUR exit the leaf through these stomata.
    • The shape of the leaf and the arrangement of cells optimize the internal surface area for gas exchange.
  • Gas Exchange in Plant Leaves
    Adaptations for Gas Exchange
    • Stomata are beside by GUARD CELLS that controls their opening, so gas exchange only occurs when necessary.
    • The FLATTENED SHAPE of the leaf increases the surface area for gas exchange.
    • Internal cell walls also contribute to a larger exchange surface, with air spaces to assist DIFFUSION.
  • Nutrient Absorption in the Small Intestine
    Villi Increase Surface Area
    • The SMALL INTESTINE boosts absorption efficiency through tiny projections (a thing that extends outwards from something else) called VILLI that expand the surface area for nutrient absorption into the blood.
    • villi consists of a SINGLE LAYER OF SURFACE CELLS and a rich supply of BLOOD CAPILLARIES for quick absorption of digested nutrients.  
  • no gaps between cells.
    • Has many microvilli to increase surface area.
    • wall of villus only one cell thin and capillaries are close to surface, so short pathway.
    • good blood supply to transport food molecules to the body and maintain a diffusion gradient.
    • cells have many mitochondria, where respiration takes place as active transport requires energy to absorb food.
  • red blood cells is the part of blood that carries the most oxygen.
  • Alveoli provides a large surface area of gas exchange.
    give other ways the lungs are adapted of efficient GAS EXCHANGE.
    • wall of alveolus are one cell thick.
    • wall of capillary are one cell thick.
    • cells of capillary wall are thin
    • good blood supply
    • well ventilated
    • short distance between alveolus and blood
  • SA:V of X: 2.4x10^-7 : 8x10^-12
    SA:V of Y: 726 : 1331
    so diffusion distance is longer in multicellular organism, so diffusion rate per unit volume is slower in a multicellular organism.
  • ACTIVE TRANSPORT
    the net movement of particles from an area of LOW concentration to an area of HIGH concentration using energy from RESPIRATION.
  • CONCENTRATION GRADIENT
    difference in concentration between the two areas.
    • Active transport involves particles moving AGAINST a concentration gradient and it is NOT a PASSIVE process like diffusion.
  • Examples of active transport:
    • Humans absorbing GLUCOSE from the gut.
    • Root cells to take in MINERALS
  • Root cells using active transport to take in MINERALS:
    • Minerals are usually at a higher concentration in root hair cells than in the surrounding soil.
    • Since diffusion can't occur against the concentration gradient, root hair cells use ACTIVE TRANSPORT to absorb minerals from the surrounding soil.
    • This allows plants to absorb nutrients from a low concentration in the soil.
  • CONCENTRATION GRADIENT
    Difference in concentration between the two areas.
  • Humans using active transport to absorb GLUCOSE from the gut.
    • In the human gut, when there's a lower concentration of nutrients compared to the blood, ACTIVE TRANSPORT allows nutrients to be absorbed into the bloodstream.
    • This is to provide ENERGY to our cells.
  • Because the phloem cells has a higher concentration than the leaf cell so sugars move into the phloem cell by active transport, which requires energy, and the companion cell contains mitochondria where respiration occurs.
  • explain what the results in the table above show about how nitrate ions are absorbed.
    more nitrate ions are absorbed in the presence of oxygen, which they are absorbed by active transport, which requires energy from respiration, so some nitrate ions absorbed were requiring energy from anaerobic respiration.
  • Plants need nitrate ions in order to make protein, but a plant is in soiled flooded with water.
    Why can't the plant absorb enough nitrate ions?
    ions are absorbed by active transport, which is the movement of ions from a low to high concentration and it requires energy from respiration but respiration need oxygens and there's no oxygen in water-flooded soil.