Pearson Edexcel GCSE (9-1) Physical Education (1PE0) · Spec C1 1.2.6 and C1 1.2.7
The respiratory system and gas exchange
Read the notes, then try the questions. Each one is marked the moment you press Check, and shows the right answer and why.
Key ideas
- Air travels down the trachea, into two bronchi, then smaller bronchioles, and ends at the alveoli.
- To breathe in, the diaphragm contracts and flattens and the external intercostals lift the ribs up and out. The chest gets bigger, the pressure falls and air flows in.
- Gas exchange happens by diffusion. Oxygen moves from the alveoli into the capillaries because there is more of it in the alveoli. Carbon dioxide moves the other way.
- Alveoli are good for gas exchange because their walls are one cell thick and they have a rich blood supply of capillaries.
- Inhaled air is about 21% oxygen, 0.04% carbon dioxide and 79% nitrogen. Exhaled air is about 16% oxygen and 4% carbon dioxide.
Key terms
- Tidal volume
- The air breathed in or out in one normal breath.
- Vital capacity
- The most air you can breathe out after breathing in as deeply as you can.
- Residual volume
- The air left in the lungs after the biggest breath out.
- Diffusion
- Movement from where there is a lot of something to where there is less.
- Alveoli
- Tiny air sacs where gas exchange takes place.
Common mistakes
- Saying we breathe in oxygen and the oxygen 'turns into' carbon dioxide. Oxygen goes into the blood. Carbon dioxide is made in the body and removed.
- Mixing up tidal volume and residual volume.
- Saying gases move from low to high concentration. Diffusion is from high to low.
Exam tip
'Describe' questions on breathing need the steps in order: diaphragm contracts and flattens, ribs move up and out, chest volume rises, pressure falls, air flows in. Use the exact percentages if a gas question gives a table.
Free practice questions
6 questions, 12 marks. Answer, then press Check. The marking guide explains how the marks are worked out. Nothing is saved.
- Question 1 · Multiple choice[1 mark]
Which structure carries air from the throat down towards the two lungs?
- Question 2 · Multiple choice[1 mark]
Which gas makes up most of the air a footballer breathes out?
- Question 3 · Multiple choice[1 mark]
Which lung volume is the air that stays in the lungs after the biggest possible breath out?
- Question 4 · Fill the gaps[1 mark]
The volume of air breathed in or out in one normal breath is the ___ volume.
Word bank: residual · reserve · tidal · vital
- Question 5 · Matching[4 marks]
Match each gas to its approximate percentage.
- Question 6 · Matching[4 marks]
Match each part of the respiratory system to its job.