Neco 2025 Biology Question 4

Practice essay / theory question 4 from the 2025 Neco Biology examination. This question covers respiration, gas exchange, ventilation .

Neco 2025 Biology Essay / Theory

Topics: respiration gas exchange ventilation

Question 4 NECO • 2025 • BIOLOGY • essay

The diagram shows the human respiratory system with the structures labelled as follows: A – nasal cavity, B – pharynx, C – larynx, D – trachea, E – primary bronchi, F – lungs, G – bronchioles, H – alveoli, I – diaphragm. Use the diagram to answer the following questions.

Question Parts

( a )

Describe the complete pathway of air from the external environment to the alveoli, naming each labelled structure it passes through.

( b )

Atmospheric pressure at sea level is 1.00 atm and the fraction of oxygen in dry air is 0.21. The water vapour pressure in the alveoli at body temperature (37 °C) is 0.047 atm. Using Dalton’s law, calculate the partial pressure of oxygen in the alveolar air (PAO₂). Show all steps.

( c )

At rest a person consumes 0.25 L of O₂ per minute and has an alveolar ventilation of 4 L min⁻¹. During intense exercise the O₂ consumption rises to 2.5 L min⁻¹. Assuming that the rate of oxygen uptake follows Fick’s law \(V_{O2}=k\frac{A\Delta P}{d}\) and that the surface area (A = 70 m²), diffusion distance (d = 0.5 µm) and the constant k remain unchanged, estimate the alveolar ventilation required during exercise. Show the reasoning you use.

( d )

Explain the role of the diaphragm (I) in normal ventilation and discuss the likely respiratory consequences if the diaphragm were paralyzed.

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About This Question

This is Neco 2025 Biology Question 4. It is one of the essay questions from the 2025 Neco Biology examination.

The question covers respiration, gas exchange, ventilation .

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