11.1

Gas exchange in humans

Cambridge IGCSE Biology (0610)  · Unit 11: Gas exchange in humans  · 12 flashcards

Gas exchange in humans is topic 11.1 in the Cambridge IGCSE Biology (0610) syllabus , positioned in Unit 11 — Gas exchange in humans .

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across 19 questions worth 241 marks (around 3.6% of all Biology marks in those years).

The deck below contains 12 flashcards — 5 key concepts, 3 process cards, 2 application cards and 2 identification cards — covering the precise wording mark schemes reward.

What the Cambridge 0610 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Describe Describe the features of gas exchange surfaces in humans, limited to: large surface area, thin surface, good blood supply and good ventilation with air
  2. Identify Identify in diagrams and images the following parts of the breathing system: lungs, diaphragm, ribs, intercostal muscles, larynx, trachea, bronchi, bronchioles, alveoli and associated capillaries
  3. Investigate Investigate the differences in composition between inspired and expired air using limewater as a test for carbon dioxide
  4. Describe Describe the differences in composition between inspired and expired air, limited to: oxygen, carbon dioxide and water vapour
  5. Investigate Investigate and describe the effects of physical activity on the rate and depth of breathing
  6. Identify Identify in diagrams and images the internal and external intercostal muscles Supplement
  7. State State the function of cartilage in the trachea Supplement
  8. Explain Explain the role of the ribs, the internal and external intercostal muscles and the diaphragm in producing volume and pressure changes in the thorax leading to the ventilation of the lungs Supplement
  9. Explain Explain the differences in composition between inspired and expired air Supplement
  10. Explain Explain the link between physical activity and the rate and depth of breathing in terms of: an increased carbon dioxide concentration in the blood, which is detected by the brain, leading to an increased rate and greater depth of breathing Supplement
  11. Explain Explain the role of goblet cells, mucus and ciliated cells in protecting the breathing system from pathogens and particles Supplement
Key Concept Flip

List four key features of gas exchange surfaces in humans.

Answer Flip

Large surface area (alveoli), thin surface (one-cell thick alveolar walls), good blood supply (dense capillary network), and good ventilation with air (breathing mechanism).

Key Concept Flip

Name the main parts of the human breathing system.

Answer Flip

Lungs, diaphragm, ribs, intercostal muscles, larynx, trachea, bronchi, bronchioles, alveoli, and associated capillaries.

Key Concept Flip

What happens to limewater when carbon dioxide is bubbled through it?

Answer Flip

Limewater turns milky or cloudy in the presence of carbon dioxide. This is a common test to detect the presence of carbon dioxide in expired air.

Key Concept Flip

What are the main differences in composition between inspired and expired air?

Answer Flip

Expired air has less oxygen, more carbon dioxide, and more water vapor than inspired air. This occurs because oxygen is used in respiration and carbon dioxide is produced as a waste product, also some water is produced.

Key Concept Flip

What happens to the rate and depth of breathing during physical activity?

Answer Flip

Both the rate and depth of breathing increase during physical activity. This is to supply more oxygen to the muscles and remove the increased carbon dioxide produced by respiration.

Key Concept Flip

Where are the internal and external intercostal muscles located?

Answer Flip

Internal and external intercostal muscles are located between the ribs. They play a role in raising and lowering the rib cage during ventilation.

Key Concept Flip

What is the function of cartilage rings in the trachea?

Answer Flip

Cartilage rings provide support to the trachea, preventing it from collapsing, especially during inhalation when pressure decreases. This ensures a clear airway for efficient gas exchange.

Example: without cartilage rings, the trachea could collapse during vigorous exercise when breathing rate increases, restricting airflow to the lungs.
Key Concept Flip

Explain how the ribs, intercostal muscles, and diaphragm work together during inhalation.

Answer Flip

During inhalation, the diaphragm contracts and flattens, the external intercostal muscles contract, raising the ribs. These actions increase the volume of the thorax, decreasing pressure and drawing air into the lungs.

Key Concept Flip

Explain the differences in composition between inspired and expired air in more detail.

Answer Flip

Inspired air is about 21% oxygen, 0.04% carbon dioxide, and variable water vapor. Expired air is about 16% oxygen, 4% carbon dioxide, and saturated with water vapor, due to respiration.

Key Concept Flip

How does increased carbon dioxide concentration in the blood affect breathing?

Answer Flip

Increased carbon dioxide concentration is detected by the brain, which stimulates an increased rate and depth of breathing. This helps to remove excess carbon dioxide and restore blood pH balance.

Key Concept Flip

Describe the roles of goblet cells, mucus, and ciliated cells in protecting the breathing system.

Answer Flip

Goblet cells secrete mucus, which traps pathogens and particles. Ciliated cells have tiny hairs (cilia) that sweep the mucus and trapped particles upwards, away from the lungs, to be swallowed or expelled.

Key Concept Flip

How does exercise impact the concentration of carbon dioxide in the blood, and consequently, breathing?

Answer Flip

During exercise, muscle cells respire more, producing more carbon dioxide. This increases the carbon dioxide concentration in the blood. The brain detects this increase and signals the body to increase the rate and depth of breathing.

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10.1 Diseases and immunity 12.1 Respiration

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Cambridge syllabus keywords to use in your answers

These are the official Cambridge 0610 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.

gas exchange lungs trachea bronchus bronchiole alveolus alveoli breathing ventilation inspiration expiration diaphragm intercostal muscle rib rib cage thorax diffusion surface area thin wall moist oxygen carbon dioxide capillary smoking tar nicotine emphysema bronchitis lung cancer

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