B8

• 8.1 Describe the need to transport substances into and out of a range of organisms, including oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea

  All organisms must take in substances that they need from the environment and get rid of any waste products.
• 8.1 Describe the need to transport substances into and out of a range of organisms, including oxygen and carbon dioxide

  Cells need oxygen for aerobic respiration, which produces carbon dioxide as a waste product. These two gases move between cells and the environment by diffusion.
• 8.1 Describe the need to transport substances into and out of a range of organisms, including water and dissolved food molecules

  Water is taken up by cells by osmosis. In animals, dissolved food molecules (the products of digestion) and mineral ions diffuse along with i
• 8.1 Describe the need to transport substances into and out of a range of organisms, including urea

  Urea (a waste product produced by excess amino acid breakdown) diffuses from cells to the blood plasma for removal from the body by the kidneys.
• 8.2 Explain the need for exchange surfaces and a transport system in multicellular organisms including the calculation of surface area:volume ratio

  Multicellular organisms have a smaller surface area compared to their volume. This makes it difficult to exchange enough substances to supply their entire volume across their body. So there are exchange surfaces to allow for efficient diffusion and a mass transport system to move substances between the exchange surface and the rest of the body.
• 8.3 Explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

  The alveoli are specialised to maximise the diffusion of oxygen and carbon dioxide.

  - A moist lining for dissolving gases.

  - A good blood supply to maintain the concentration gradients of oxygen and carbon dioxide.

  - Very thin walls - minimising the distance that gases have to move.

  - An enormous surface area.
• 8.6 Explain how the structure of the blood is related to its function:

  a red blood cells (erythrocytes)

  a) - erythrocytes have no nucleus so there is more space for haemoglobin. the cells are shaped like discs with a dimple in each side. this shape allows a large surface area : volume ratio for oxygen to diffuse in and out
• 8.6 Explain how the structure of the blood is related to its function:

  b white blood cells (phagocytes and lymphocytes)

  b) - phagocytes surround foreign cells and digest them. lymphocytes produce proteins called antibodies that stick to foreign cells and help destroy them
• 8.6 Explain how the structure of the blood is related to its function:

  c plasma


  c) - plasma carries dissolved substances such as glucose, carbon dioxide and urea
• 8.6 Explain how the structure of the blood is related to its function:

  d platelets


  d) - platelets produce substances needed to clot the blood at the site of an injury
• 8.7 Explain how the structure of the blood vessels is related to their function: Arterys


  -Carry blood away from the heart (usually oxygenated blood, except for the pulmonary artery)

  -Thick muscular walls to withstand blood flowing at high pressure as it leaves the heart; the largest artery is the aorta

  -small lumen
• 8.7 Explain how the structure of the blood vessels is related to their function: Veins

  -Carry blood towards the heart (usually deoxygenated blood, except for the pulmonary vein)

  -thin walls, large lumen

  -contains valves to prevent backflow of blood
• 8.7 Explain how the structure of the blood vessels is related to their function: Capillaries


  -Allows diffusion of gases and nutrients from blood into the body cells

  -very thin walls (only one cell thick)

  -very small lumen, only allows blood to pass through one cell at a time

  -Walls are made of semi-permeable membrane to allow transport of gases and nutrients into and out of the blood
• 8.8 Explain how the structure of the heart and circulatory system is related to its function, including the role of the major blood vessels, the valves and the relative thickness of chamber walls

  1. Deoxygenated blood flows through right atrium and then into right ventricle which pumps it to the lungs

  2. Oxygenated blood flows into left atrium and into left ventricle which pumps oxygenated blood around body

  
  

  STRUCTURE

  - Muscular walls to provide a strong heartbeat- Muscular wall of left ventricle is thicker because blood needs to be pumped around body rather than just to lung like right ventricle

  - The 4 chambers separate the oxygenated blood from the deoxygenated blood- Valves make sure blood does not flow backwards (prevents backflow)

  - Coronary arteries cover the heart to provide its own oxygenated blood supply

  
  

  PROCESS:

  1. Blood flows through the right atrium through the vena cava and left atrium through the pulmonary vein

  2. Atria contracts, forcing blood into the ventricles

  3. Ventricles then contract, pushing blood in the right ventricle into the pulmonary artery to be taken to lungs and blood in left ventricle to the aorta to be taken around the body

  4. As this happens, valves make sure to close to prevent backflow
• 8.9 Describe cellular respiration


  an exothermic reaction which occurs continuously in living cells to release energy for metabolic processes, including aerobic and anaerobic respiration
• 8.10 Compare the process of aerobic respiration with the process of anaerobic respiration

  -aerobic respiration uses oxygen / anaerobic does not use oxygen

  -aerobic respiration releases more energy / anaerobic releases less energy

  -aerobic produces {carbon dioxide / water} / anaerobic respiration produces lactic acid
• 8.11 Core Practical: Investigate the rate of respiration in living organisms

  By measuring amount of oxygen consumed by organisms in a given time, you can calculate rate of respiration

  
  

  1. Soda lime granules added to two test tubes. This absorbs CO2 produced by respiring woodlice

  2. Ball of cotton is placed above soda lime in each tube. Woodlice are placed on top of cotton wool in one tube and also glass beads with the same mass as the woodlice are used in control tube

  3. Respirometer is then set up

  4. Syringe is used to set the fluid in the manometer to a known level

  5. Apparatus is the left for a period of time in water bath set to 15 degrees

  6. There will be a decrease in volume of air in the test tube containing woodlice because woodlice use up oxygen in tube as they respire (The CO2 the release is absorbed by sodalime so does not affect experiment

  7. The decrease in volume reduces pressure in tube causing coloured liquid to move towards test tube containing the woodlice

  8. Distance moved by the liquid in a given time is measured and this can be used to calculate the volume of oxygen taken in by woodlice per minute

  9. Repeat previous steps and set the water bath at different temperatures which will allow to see how changing the temperature affects the rate of respiration
• 8.12 Calculate heart rate, stroke volume and cardiac output, using the equation cardiac output = stroke volume × heart rate


  cardiac output = stroke volume × heart rate (heart rate=bpm, volume=cm3)