Describe the path taken by an oxygen molecule from the nose to the alveoli.

WJEC GCSE Biology (Wales) — 1.2.2 The respiratory system · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Air passes through the trachea (windpipe) → the trachea divides into two main bronchi, one to each lung → the bronchi branch into smaller bronchioles → the bronchioles terminate in alveoli (air sacs) where gas exchange occurs

Examiner tips

Use the exact anatomical terms (trachea, bronchi, bronchioles, alveoli)
Show the sequence clearly, e.g. arrow or ‘→’
Mention that gas exchange takes place in the alveoli
Keep the answer concise – one sentence per step

Common mistakes

Using ‘lungs’ instead of ‘bronchi’ for the first division
Omitting the step from bronchi to bronchioles
Not specifying that gas exchange occurs in the alveoli

Mark scheme (4 marks)

Air passes through the trachea (windpipe)
The trachea divides / branches into two bronchi (one to each lung)
Bronchi divide into smaller bronchioles
Bronchioles lead to / end at the alveoli (air sacs) where gas exchange occurs

Key terms in this question

alveoli