Exam qs

• Describe how oxygen in the air reaches capillaries surrounding alveoli in lungs (4)

  • Air enters the trachea, bronchi and bronchioles
  • oxygen moves down a pressure gradient
  • oxygen moves down a diffusion gradient
  • across alveolar epithelium
  • across capillary endothelium
• Explain why death of alveolar epithelium cells reduces gas exchange in human lungs (3)

  • reduced surface area
  • increased distance for diffusion
  • reduced rate of gas exchange
• Pulmonary Ventilation is the total volume of air that is moved into the lungs during one minute:

  • Pulmonary ventilation rate = tidal volume x breathing rate
  • Tidal volume = volume of air taken in each breath (at rest)
  • Breathing rate = number of breaths per minute
• Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between blood and the alveoli (3)

  • less carbon dioxide exhaled
  • so reduced diffusion gradient between blood and alveoli
  • less/slower movement of carbon dioxide out of blood.
• Explain why oxygen uptake is a measure of metabolic rate in organisms (1)

  • oxygen is used in respiration which is a metabolic reaction
• Explain 3 ways in which an insect’s tracheal system is adapted for efficient gas exchange (3)

  • highly branched tracheoles so large surface area
  • tracheoles are thin so short diffusion distance
  • trachea provides tubes full of air so fast diffusion
• Describe the pathway taken by an oxygen molecule from an alveolus to the blood (2)

  • oxygen diffuses across alveolar epithelium
  • across capillary endothelium and into haemoglobin in blood.
• Describe the gross structure of the human gas exchange system and how we breathe in and out (6)

  • trachea, bronchi, bronchioles and alveoli
  • breathing in - diaphragm contracts and external intercostal muscles contracts
  • causes volume to increase and pressure decreases in thoracic cavity
  • breathing out - diaphragm relaxes and internal intercostal muscles contract
  • causes volume to decrease and pressure increase in thoracic cavity
• Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.

  • Many llamellae so large surface area
  • thin so short diffusion pathway
• Explain how the counter current mechanism in fish gills ensures the maximum amount of the oxygen passes into the blood flowing through the gills. (3)

  • water and blood flow in opposite directions
  • blood always passes over water with a higher oxygen concentration
  • diffusion gradient maintained throughout length of gill
• A fish uses its gills to absorb oxygen from water. Explain how the gills of a fish are adapted for efficient gas exchange. (6)

  • large surface area provided by lamellae
  • thin distance between water and blood
  • water and blood flow in opposite directions
  • this maintains concentration gradient along the gill lamellae
  • circulation replaces blood saturated with oxygen
  • ventilation replaces water that has had its oxygen removed
• Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why. (2)

  • more oxygen enters
  • maintaining the concentration gradient
• Explain why ventilation of lungs increases the efficiency of gas exchange (2)

  • removes carbon dioxide and brings in more oxygen
  • maintains diffusion gradient
  • between alveoli and blood
• Describe a method you could use to find the surface area of a leaf (3)

  • draw around leaf on graph paper
  • count squares
  • multiply by 2 (for upper and lower leaf surface)
• Describe how the structure of the insect gas exchange system:

  • provides cells with sufficient oxygen
  • limits water loss

  Explain your answers (5)

  • spiracles, tracheae, tracheoles
  • spiracles allow diffusion of oxygen
  • tracheoles are highly branched so large surface area
  • tracheole walls are thin so short diffusion distance
  • tracheole walls are permeable to oxygen
  • chitin exoskeleton so reduce water loss
  • spiracles can close to prevent water loss
  • hairs around spiracles reduce water loss
• Describe how humans breathe in and out (5)

  Breathing in:

  • diaphragm contracts and diaphragm flattens
  • external intercostal muscles contract and ribcage pulled up
  • volume increases and pressure decreases in thoracic cavity

  Breathing out:

  • diaphragm relaxes and diaphragm moves up
  • internal intercostal muscles contract and ribcage moves downwards
  • volume decreases and pressure increases in thoracic cavity