Biology

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  • Created by: Suhana97
  • Created on: 28-02-15 18:18
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  • Transport around the Body
    • Transport Sytstems
      • Diffusion - a method of moving substances in and out of cells.
        • Rate of Diffusion
          • Surface Area x Conc Gradient / Distance
        • Smaller surface area to volume ratio the less effective diffusion
          • Diffusion through the surface is too slow, requires a mass transport system and specialised organs
      • Mass Transport System
        • transfer substances by diffusion, osmosis and active transport
          • System of vessels - widespread and branching
          • Substances moved in right direction
          • Moving materials fast enough
    • Water in Living Organisms
      • Water is the medium in which all reactions take place.
        • Water molecules are slightly polarised, oxygen is slghtly negative and hydrogen is slightly positive
          • separation of charges is called 'dipole' causing hydrogen bonds and weak electrostatic forces to form.
        • Importance of water.
          • Less dense as a solid because of more space between molecules.
            • Arctic ecosystems float - rigid structure (expansion)
          • High specific heat capacity - fairly stable temperature
          • Present in 3 states - allows water cycle to function
          • Amphoteric - ideal medium as it acts as both an acid (forms H+ ions) and base (forms OH- ions)
          • Good solvent - essential role in transport.
            • Ionic and polar substances would dissolve in water
            • Non-polar substances form colloids.
          • High Surface Tension - hydrogen bonds pull water molecules together resembling a stretched membrane.
          • Buffer - water is able to accept and donate protons
          • Immiscible with hydrophobic molecules
            • Allows membrane to form controlling the movement into and out of cells.
          • High latent heat of evaporation - intake or expel of heat without temp change
            • Evaporation has a cooling effect and little water is needed to lose a lot of heat.
    • Blood Circulation
      • Circulatory system is when heart pumps blood around the body in blood vessels.
        • Open circulatory system - blood circulating in large open spaces
        • Closed circulatory system- blood circulation within tubes.
          • Systemic circulation - carries oxygenated blood from the heart to the body
          • Pulmonary circulation - carries deoxygenate-d blood from the heart to the lungs
      • BLOOD VESSELS
        • ARTERY - carry oxygenated high pressure blood away from the heart.
          • Lumen diameter decreases the further away from the heart, relatively small
          • Arteries close to the heart contain more elastic fibres to stretch when higher volume of blood is forced into it
          • Arteries further from the heart contain thick muscle layer to withstand high pressure
            • Muscle fibres contract or relax to to change the size of the lumen, controlling blood flow.
          • Protective collagen layer
          • Round shape
        • CAPILLARY - link between arterioles and venules, adapted for exchange.
          • Branch between cells for diffusion - no cell is far from a capillary.
          • more opportunity for rapid diffusion as blood travel slowly through capillaries
          • One cell thick, very thin walls containing no collagen, smooth muscle or elastic fibre
          • Blood entering the capillary network is oxygenated , by the time it leaves it is deoxygenate-d.
        • VEIN - carry deoxygenated low pressure blood towards the heart.
          • Blood reservoir
          • Only two veins carry blood back to the heart  - inferior and superior vena cava
          • Throughout the venous system there are semilunar valves - prevent backflow
            • Valves are infoldings of the inner walls of the vein
          • Thin muscle layer and minimum elastic fibre, not round shape
          • Protective collagen layer
          • Large lumen decreases effect of friction.
    • Blood Clotting Mechanism
      • Blood clotting mechanism seals up damaged blood vessels to minimise blood loss and prevent pathogen entering
      • Contact between the platelets and the components of the tissue from the cut vessel causes platelets to break out in large numbers.
        • Release substances -
          • Serotonin - causes smooth muscle to contract narrowing the vessel to reduce blood flow
          • Thromboplastin - an enzyme sets a cascade of events that forms the clot.
            • Thromboplastin catalyses the large protein prothrombin into enzyme thrombin, with the presence of calcium ions
              • Thrombin catalyses the protein fibrinogen into fibrin, this forms a mesh of fibres.
    • Transporting Oxygen and Carbon Dioxide
      • OXYGEN
        • Concentration of oxygen in the erythrocytes when the blood enters the lungs is low because blood has been given to body tissues.
          • Oxygen diffuses into the erythrocytes from the air and is bound to the haemoglobin, maintaining a steep concentration gradient from the air to the lungs - more oxygen is diffused.
        • Oxygen levels  in the body tissues is low because of cellular respiration.
          • Oxygen concentration is higher in the erythrocytes than in the body tissue so oxygen diffuses into the body tissues, down its concentration gradient.
        • Haemoglobin packed in the erythrocytes transports oxygen.
      • CARBON DIOXIDE
        • Carbon dioxide diffuses from the respiring body tissue into the blood.
        • 10-20% combines with haemoglobin to form carbaminoha-emoglobin.
        • 5% is carried in solution in the plasma
        • most is carried in the cytoplasm of the erythrocytes as hydrogen -carbonate ions
        • Reacts with water to form carbonic acid with the help of the enzyme carbonic anhydrase.
          • Carbon dioxide concentration is low in the lungs so carbonic anhydrase catalyses the reverse reaction, freeing carbon dioxide out into the lungs from the blood.
        • CO2 + H2O = H2CO3= HCO3- + H+
    • Role of the Blood
      • The blood is the transport medium passing through vessels, this is called 'circulation'
      • Job consists of; carrying chemicals/ substances, forming the defense system and distributing heat.
      • Components of the Blood
        • Plasma - main component of the blood largely of water,
          • Contains dissolved substances to be transported and fibrinogen - vital for the clotting of blood.
          • transports digested food and excretory products, and chemical messages; helps to mantain steady temperature.
        • Erythrocytes - red blood cells, biconcave discs, 5million per mm3, 120 day lifespan and no nucleus
          • Contain haemoglobin, a red pigament that carries oxygen and is formed in the red bone marrow of the short bones.
          • transports oxygen to the cells, large surface area to volume ratio enabling rapid diffusion of oxygen. carries some carbon dioxide back to the lungs.
        • Leucocytes - white blood cells, larger than erythrocytes, 4/11,000 per mm3, contain a nucleus and colourless cytoplasm.
          • Can squeeze through tiny blood vessels by changing shape, formed in the white bone arrow of the long bones, main function is to defend the body.
          • Defend against disease by making antibodies- that destroy, antitoxins- that neutralise and engulfment of pathogens which is known as phagocytosis.
        • Platelets - tiny fragments of megakaryocy-tes found in the bone marrow, 150/400,000 per mm3, involved in the blood clotting process.
  • Transport System: substances need to be moved from one place to another
    • Transport Sytstems
      • Diffusion - a method of moving substances in and out of cells.
        • Rate of Diffusion
          • Surface Area x Conc Gradient / Distance
        • Smaller surface area to volume ratio the less effective diffusion
          • Diffusion through the surface is too slow, requires a mass transport system and specialised organs
      • Mass Transport System
        • transfer substances by diffusion, osmosis and active transport
          • System of vessels - widespread and branching
          • Substances moved in right direction
          • Moving materials fast enough
    • Substances are transported from inside the organism to outside to remove waste products.
    • Substances are transported from outside the organism to inside for necessary products.
  • Surface are to volume ratios determines whether diffusion alone would work.
    • Suitable transport medium

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