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7.2.7Unit 3: Practical Skills in Biology I

Core Practical 17: The Effects of Exercise — IAL Edexcel Linear Revision Notes & Topical Questions

5 min read 5 parts Lesson 26 of 27 Unit quiz

📚 IAL Edexcel Linear Hub / Topical Revision
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Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
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Section 1 of 5Measures of Breathing

Tidal volume
  • Tidal volume The volume of air breathed in or out during one normal breath at rest.
Breathing rate
  • Breathing rate The number of breaths taken in one minute, with one breath being a single in-and-out cycle.
Minute ventilation
  • Minute ventilation The volume of air breathed in or out per minute, equal to tidal volume × breathing rate.
Oxygen consumption
  • Oxygen consumption The volume of oxygen used by the body in a given time.
Vital capacity
  • Vital capacity The maximum volume of air that can be breathed out after the deepest breath in.
Residual volume
  • Residual volume The air that always remains in the lungs after the strongest exhalation.

Section 2 of 5Method and Safety

1
A seated subject breathes through a mouthpiece connected to a spirometer containing medical oxygen, with soda lime in the circuit.
2
Record the trace for one minute at rest, as the soda lime absorbs the exhaled carbon dioxide.
3
The subject then exercises for two minutes, for example on a treadmill, while the chamber is topped up with oxygen.
4
Immediately after exercise the subject breathes into the spirometer for a further minute and the trace is recorded.
5
Compare the results before and after exercise, and take precautions such as a clean mouthpiece, a healthy subject and stopping if distressed.

Section 3 of 5Analysing the Trace

Analysing the Trace
Breathing rate
  • Breathing rate Count the number of peaks in one minute.
Tidal volume
  • Tidal volume Measure the difference between the top of a peak and the bottom of the following trough.
Oxygen consumption
  • Oxygen consumption Because the soda lime removes CO₂, the total gas volume falls as oxygen is used,
    • and the downward slope of the trace gives the rate.
Expected result
  • Expected result After exercise tidal volume, breathing rate, minute ventilation and oxygen consumption are all higher.

Section 4 of 5Worked Example

Question

  • At rest a subject's trace shows peaks of 3.0 dm³ and troughs of 2.5 dm³ with 12 breaths in one minute.
  • After exercise the tidal volume is 1.5 dm³ and the rate is 20 breaths per minute.
  • Calculate the minute ventilation at rest and after exercise.

  1. Resting tidal volume = 3.0 − 2.5 = 0.5 dm³.
  2. Resting ventilation = 0.5 × 12 = 6.0 dm³ min⁻¹.
  3. After exercise = 1.5 × 20 = 30 dm³ min⁻¹.

Answer 6.0 dm³ min⁻¹ at rest and 30 dm³ min⁻¹ after exercise, a five-fold increase.

Section 5 of 5Exam Checklist & Tips

7.2.7 – Key Points for the Exam

  • Spirometer Apparatus that records the volume of air breathed in and out over time.
  • Tidal volume Volume of air moved in a single resting breath.
  • Minute ventilation Tidal volume multiplied by breathing rate.
  • Vital capacity The greatest volume of air that can be exhaled after a maximal inhalation.

Common Mistakes

  • Counting one breath as a peak and trough pair twice.
  • Forgetting that the soda lime is there to remove the carbon dioxide being rebreathed.
  • Stating the units of ventilation as dm³ instead of dm³ min⁻¹.
  • Measuring tidal volume from the top of the graph to the zero line.

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