Gas Exchange

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  • Insects
    • BY2 - Gas Exchange (2)
      • Birds
        • Gas exchange surface = lungs.
          • Similar internal structure to mammals' lungs.
          • Thin
          • Moist
            • Permeable
        • Additional air sacks so more efficient.
          • Store oxygen.
          • Ribs moves up and down to allow them to breathe.
      • Amphibians
        • Gas exchange surface = skin and within the lungs.
          • Skin alone acts as the gas exchange surface with water or air when the creature is inactive.
          • Well developed capillary network just beneath the surface.
          • Tadpoles have gills as their gas exchange surface.
      • Reptiles
        • Pairs of ribs project from the backbone.
          • Provide support and protection to inner organs.
        • Gas exchange surface = lungs.
          • Large surface area to volume ratio.
          • Thin
      • Human Respiratory System
        • Lungs
          • Lungs are internal because we need to reduce water and heat loss.
          • Inspiration
            • Intercostal muscles contract.
            • Ribs move up and out.
            • Diaphragm contracts and flattens.
            • Volume of the thorax increases.
            • Pressure of the thorax decreases.
            • Atmospheric pressure forces air into the lungs.
      • Plants
        • Leaf adaptations
          • Flat - large surface area to absorb sunlight and carbon dioxide.
          • Grow towards light source for maximum light.
          • Thin to allow light to penetrate and this is also a short diffusion pathway.
          • Cuticle and epidermis are transparent to allow light to penetrate into cells.
          • Palisade cells are elongated to be more tightly packed together to absorb more light.
          • Chloroplasts can move to get a better position for absorbing light.
          • Spongy mesophyll cells are moist for gas exchange as gases dissolve in moisture.
          • Xylem (vascular bundle) provides water for photosynthesis.
          • Waxy cuticles reduce water loss by evaporation but reduce gas exchange.
            • Guard cells can open and close to reduce water loss.
          • Stomata allow entry and exit of gases.
            • Air spaces allow circulation of gases and create a concentration gradient between inside the leaf and the atmosphere.
        • Respire during night and day so oxygen is required.
          • Carbon dioxide is required too )Photosynthesis).
            • Diffuses into leaves from the atmosphere.
          • Produced by photosynthesis - some is retained for respiration.
        • O2 + GLUCOSE --> H20 + CO2 + ATP.
        • H20 + CO2 --> O2 + GLUCOSE
        • Stomata
          • Pores found on the lower epidermis of the leaf.
          • Allow gas exchange.
            • Controls water loss.
          • Opening of Stomata
            • 1. K+ is actively pumped into guard cells and starch is converted into malate.
              • This lowers water potential.
              • 2. Water moves from a high water potential (epidermal cells) to a low water potential (guard cells) by osmosis.
                • 3. Guard cells become TURGID.
                  • 4. Inner wall of the guard cell is thicker/inelastic than the outer wall and the guard cells bend away from each other.
                    • Cyanide stops active transport into the guard cells because it is a non-competitive respiratory inhibitor.
                • Opposite steps occur for the closing of the stomata.
    • Diffusion into the body is difficult because of their small surface area to volume ratio.
      • Waterproof exoskeleton made of chitin.
        • Prevents diffusion of gases through the skin so a different gas surface has evolved.
    • Air moves in and out through spiracles (holes along the abdomen).
      • Paired spiracles transfer gas in branched, chitin-lined tubes called tracheae.
        • Gas exchange takes place in trachioles (where oxygen passes into cells).
    • Functions of Spiracles
      • Control gas exchange.
      • Reduce water loss.
      • Gas exchange occurs directly in the tissue as there is no blood.
      • Thorax spiracles open first then the abdomen spiracles.
        • Thorax spiracles act as a pump to pull air in.
      • Flight - movement of the abdomen ventilates the tracheae.
  • Moist
    • Permeable
    • Gas exchange surface = skin and within the lungs.
      • Skin alone acts as the gas exchange surface with water or air when the creature is inactive.
      • Well developed capillary network just beneath the surface.
      • Tadpoles have gills as their gas exchange surface.
  • Features
    • Large surface area to volume ratio
      • Alveoli are large in numbers.
    • Thin
      • Alveoli have thin walls and therefore a short diffusion pathway.
    • Moist
      • Permeable.
      • Gases dissolve.
    • Lungs
      • Lungs are internal because we need to reduce water and heat loss.
      • Inspiration
        • Intercostal muscles contract.
        • Ribs move up and out.
        • Diaphragm contracts and flattens.
        • Volume of the thorax increases.
        • Pressure of the thorax decreases.
        • Atmospheric pressure forces air into the lungs.
  • Each pore is surrounded by 2 guard cells.
    • Unevenly thickened walls.
      • Outer wall is thin and inner wall is thick.
    • Contain chloroplast.
    • Stomata
      • Pores found on the lower epidermis of the leaf.
      • Allow gas exchange.
        • Controls water loss.
      • Opening of Stomata
        • 1. K+ is actively pumped into guard cells and starch is converted into malate.
          • This lowers water potential.
          • 2. Water moves from a high water potential (epidermal cells) to a low water potential (guard cells) by osmosis.
            • 3. Guard cells become TURGID.
              • 4. Inner wall of the guard cell is thicker/inelastic than the outer wall and the guard cells bend away from each other.
                • Cyanide stops active transport into the guard cells because it is a non-competitive respiratory inhibitor.
            • Opposite steps occur for the closing of the stomata.

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