1.2 Gas exchange

Exercise 1 Using connecting words In this exercise, you choose the best connecting word to complete sentences about gas exchange. Look at Connecting words in the English skills and support section for information about connecting words. Choose a connecting word to complete each sentence. Choose from the following words. Use each word at least once. and because but so a Oxygen can easily diffuse from the alveoli into the capillaries ........................... they are very close together. b Carbon dioxide is produced in all the cells in the body by respiration, .......................... expired air contains more carbon dioxide than inspired air. c A large volume of air passes through the trachea, ....................... gas exchange does not happen there. d Gas exchange is the movement of oxygen into the blood ......................... the movement of carbon dioxide out of the blood. e An analogy is a comparison between one thing and another, ............... the two things are not exactly the same. SAMPLE

Exercise 2 Answering questions

It is important to do what the command word in a question asks you to do. In this exercise, you practise responding to three different command words. a Name the substance inside red blood cells that helps them to carry oxygen. ………………………………………………………………………………………. b Describe how oxygen moves from the alveoli into the blood. ………………………………………………………………………………………. ………………………………………………………………………………………. c Explain why we can use limewater to compare how much carbon dioxide there is in inspired air and expired air. ………………………………………………………………………………………. ………………………………………………………………………………………. ………………………………………………………………………………………. SAMPLE