Topic Nine (1.9): Respiratory system and gas exchange

Topics Icon.png Objectives

By the end of this topic, you should be able to:

  • explain how alveoli are adapted for gas exchange.

Revision Tasks Icon.png Retrieval starter question

  • Can you name the enzyme that will break down protein into amino acids?

Introduction Icon.png Introduction

In this topic, you will learn that the size of an organism (the surface area) defines how quickly substances can be absorbed. Small organisms like flatworms pass substances through their bodies by diffusion. Large multicellular organisms cannot use simple diffusion; they need a gas exchange surface. You will be learning about the lungs and the alveoli. The alveoli are tiny air sacs within the lungs: this is the site for gas exchange.

Interact Icon.png Working through your course book

Reactivate activity - optional

Before applying your knowledge to new concepts in this topic, you can check your understanding of previous concepts. If you want to check your understanding and reactivate your knowledge, please complete this reactivate activity: 

  • Read page 28 of your Activate 3 coursebook and answer the Reactivate your knowledge questions at the top of page 44.

Apply your knowledge

You are now ready to apply your knowledge of diffusion. We are going to look closely at the lungs, which contain many tiny air sacs called alveoli.

  • Read pages 44-45 of your Activate 3 coursebook.
  • Watch the videos below on Gas exchange and Adaptations of the alveoli:

There are many different exchange surfaces, including alveoli for gas exchange, the villi of the small intestine for the diffusion of nutrients and leaves and stomata for the exchange of gases into and out of a plant.

  • Read B3 2.4 Information sheets A, B and C and complete the B3 2.4 Support worksheet:

READ - B3 2.4 Information sheet A: Respiratory system and gas exchange (Kerboodle)

READ - B3 2.4 Information sheet B: Respiratory system and gas exchange (Kerboodle)

READ - B3 2.4 Information sheet C: Respiratory system and gas exchange (Kerboodle)

COMPLETE - B3 2.4 Support: Respiratory system and gas exchange (Kerboodle)

[These Kerboodle documents are not available on sample course]

  • Complete Summary questions 1-5.
  • Complete the Maths skill interactive below about surface area to volume ratio. This is an important concept in Biology.

COMPLETE B3 2.4 Maths skill interactive: Respiratory systems and gas exchange: surface area to volume ratio (Kerboodle) [Not available on sample course]

Stretch Icon.png Extension activities for this topic

Answer Summary question 6 on page 45 - you can include diagrams to help you compare the exchange surfaces.

Download Icon.png Check your answers

CHECK - Topic question answers - Module One (Kerboodle)

CHECK - Student Book Answers – B3 Chapter 2 (Kerboodle)

CHECK - B3 2.4 Teacher and technician sheet: Respiratory system and gas exchange (Kerboodle)

[Not available on sample course]