Organisation

• Compare the structure of an artery with the structure of a vein. [3 marks]

  -> artery has thicker layer of muscle tissue

  -> vein has a wider lumen

  ->artery does not have valves but vein does
• Where does the pacemaker locate at? [1 mark]

  Right atrium
• What molecules are genes made of? [1 mark]

  DNA
• Explain why the result of the investigation might be inaccurate (observe colour change in solution). [1 mark]


  Observation of colour change is subjective
• Explain why test tube with bile breaks down fat quicker. [3 marks]

  -> bile emulsifies fat

  -> creates a larger surface area

  -> lipase can break down fat more effectively
• How is the volume of water lost from the leaves controlled? [1 mark]

  guard cells opening and closing the stomata
• Describe the transport of water through a plant from roots to the atmosphere. [3 marks]

  -> plant roots absorb water from soil through osmosis

  -> water travels up the plant, transported by xylem

  -> water evaporates and leave from stomata
• Define the term ‘double circulatory system’. [1 mark]

  blood enters the heart twice for every circuit around the body
• Why one ventricle is less efficient than having two ventricles? [2 marks]

  -> oxygenated and deoxygenate blood mixes

  -> less oxygen can reach the cells
• Explain why a person with a leaking heart valve has difficulty exercising. [4 marks]

  -> backflow of blood may occur

  -> less blood can be pumped out of the heart to the cells

  -> less oxygen is supplied to the cells

  -> less aerobic respiration and more anaerobic respiration

  -> less energy is released so less efficient muscle contraction

  -> less efficient removal of lactic acid

  -> lactic acid accumulates causing muscle fatigue

  -> less efficient removal of carbon dioxide
• Describe how the small intestine is adapted to efficient absorption. [5 marks]

  -> villi (projection), increases surface area

  -> small intestine is long so longer time for absorption

  -> thin villi walls, shorter diffusion distance

  -> good and efficient blood supply to maintain concentration gradient (steep)

  -> have many mitochondria to release energy for active transport