Biology

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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