BY2 - Transport In Animals (3)

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  • BY2 - Transport In Animals
    • What causes the pressure changes in the arteries?
      • Rhythmic rise and fall due to ventricular systole
      • Arteries drop in pressure because of friction with the vessel walls and blood.
      • Arterioles can dilate (widen) and constrict (narrow).
        • This affects pressure
      • Arterioles have a large total surface area which reduces pressure.
    • What causes pressure changes in the veins?
      • Non-rhythmic
        • Due to the veins being a large distance away from the heart and the aorta.
    • How does blood return to the heart?
      • Massaging effect
      • Semi-lunar valves ensure blood returns to the heart.
    • What causes pressure changes in the capillaries?
      • Decrease in pressure due to the capillaries having a large cross-sectional area.
        • Capillary bed
      • Capillary bed creates an even greater resistance to blood flow.
        • Slows blood flow
      • Drop in pressure is also due to leakage from capillaries into the tissues.
    • Red Blood Cells
      • Structure
        • Biconcave
        • No nucleus
          • Increases surface area to volume ratio
          • More room for haemoglobin.
      • Function
        • Transport oxygen from lungs to respiring tissues.
          • E.G. Muscle tissues.
    • Transport of Oxygen
      • Structure of Haemoglobin
        • Each haemoglobin carries 4 O2.
        • Haemoglobin can change its affinity for oxygen in the presence of CO2 by changing its shape.
        • Altered shape binds more loosely with O2 and releases it.
        • Myoglobin
          • More stable than haemoglobin.
          • Won't release O2 unless the partial pressures of O2 are extremely low.
          • Found in the muscles and acts as an energy store.
        • Foetal & Maternal Haemoglobin
          • Foetal haemoglobin has a higher affinity for oxygen.
          • Oxygen is absorbed from the mother.
          • Foetal haemoglobin becomes fully saturated at lower partial pressures of oxygen.
      • Process
        • Red blood cells 'load up' O2 in the lungs where the partial pressures of O2 are high.
          • Haemoglobin becomes saturated with oxygen.
        • Red blood cells carry the oxygen as oxy-haemoglobin to repiring tissues.
          • E.G. Muscles
        • Partial pressures of oxygen are low in the muscles.
          • Respiration uses up oxygen.
    • Why is the Dissociation Curve S-Shaped?
      • First molecule of O2 finds It difficult to combine with the haemoglobin.
        • This alters the shape of the haemoglobin.
      • The change in shape makes it easier for the second molecule of O2 to attach itself to the haemoglobin.
        • This once again alters the shape of the haemoglobin.
      • This change in shape makes it even easier for the third molecule of O2 to attach itself to the haemoglobin.
        • The curve levels off at the top because the joining of the fourth molecule of O2 is more difficult.
      • Haemoglobin does not easily combine with O2 at low partial pressures of O2 - it actually releases the O2 its carrying.
        • This benefits the organism because the O2 released will be used for respiration.
          • An advantage of the S-Shaped curve in the tissues is that as partial pressures of O2 decrease more O2 is released.
            • An advantage of the S--Shaped curve in the lungs is that as partial pressures of O2 increase haemoglobin becomes saturated and O2 is released less easily/readily.
      • At high partial pressures of O2 in the lungs haemoglobin becomes fully saturated with O2.
        • Haemoglobin easily picks up the O2 but does not easily release it at high partial pressures.
      • Bohr Effect
        • CO2 is constantly produced by respiring cells.
          • CO2 diffuses from the cells into the blood plasma and then into the red blood cells.
          • High partial pressures of CO2 causes haemoglobin to release the oxygen its carrying.
            • CO2 lowers blood pH which reduces the affinity the haemoglobin has for oxygen.
        • The more the curve moves to the right the less easily / readily haemoglobin picks up the O2 and it more readily releases O2
        • The higher the concentration of CO2 the more readily oxygen is released.
    • Transport Oxygen in Other Animals
      • Lugworm
        • Low metabolic rate
        • Lives in sands on the seashore.
          • Low levels of oxygen
        • Pumps seawater through its burrow.
        • Limited amount of dissolved oxygen present.
        • Has special haemoglobin that more readily picks up oxygen.
          • S-Shaped curve is more to the left when compared to human haemoglobin.
      • Llama
        • Has a greater affinity for oxygen compared with human haemoglobin.
        • Lives at high altitudes
          • Low partial pressures of O2
        • Creatures that live at high altitudes have larger numbers of red blood cells.
    • Transport of CO2
      • 1. CO2 diffuses from body cells into the plasma, then into the red blood cells.
        • CO2 combines with water to form carbonic acid (H2CO3) - the reaction is catalysed by the enzyme carbonic anhydrase.
        • 2. Carbonic acid breaks up into H+ and HCO3-. H+ lowers blood pH and causes O2 to be released.
          • HCO3- diffuse out into the plasma where they combine with sodium to form sodium hydrogen carbonate.
          • 3. H+ cause the haemoglobin to dissociate / release oxygen as H+ moves into the oxy-haemoglobin
            • 4. Oxygen diffuses out of red blood cells and into the tissues.
              • 5. H+ combine with haemoglobin to form haemo- globonic acid. (HHb).
                • 6. Outward movement of negative HCO3 ions are balanced by the inward movement of Cl- ions.
                  • This is known as chloride shift. It maintains electro-chemical neutrality.
    • Intercellular Fluid
      • The function of the capillaries is to exchange substances between the blood and cells.
      • Adaptations of Capillaries
        • Thin
        • Large cross sectional area
        • Semi-permeable (pores)
        • Blood flows slowly to allow the exchange of substances.
      • Formation of Tissue Fluid
        • Fluid movement depends upon the difference between HYDRO-STATIC pressure and OSMOTIC pressure
        • If hydrostatic pressure of the blood is higher than osmotic pressure then there will be a net flow of water out of the blood.
        • If hydrostatic pressure n the blood is lower than osmotic pressure there will be a net flow of water into the blood.
        • Osmotic pressure changes because of water (plasma) moving out of the capillary at the arterial end.
          • This reduces the water potential of the blood moving towards the venous end.
          • Water will move by osmosis from the tissue fluid back into the capillary at the venous end because water moves from a high to low water potential.
            • If fluid does not return in this way then it will drain into the m=lymphatic system via the thoracic duct which empties into a vein near the heart.
      • What happens to the blood that leaks out of the capillaries?
        • Substances that leak out are: glucose, O2, vitamins, minerals, H2O and amino acids.
        • They leak out at the arterial end of the capillary bed.
        • Large molecules won't be able to leak out e.g. red blood cells and plasma proteins.
          • The fluid that leaks out is TISSUE FLUID which surrounds the body cells.
            • It supplies cells with glucose, amino acids, minerals, vitamins and O2.
              • Tissue fluid removes waste substances from cells e.g. CO2 and urea.

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