Scheme of Work Cambridge International as & a level

Extension activity: You could set further reading on vaccination programmes using websites such as www.who.int/features/2010/smallpox/en/

Past and specimen papers

Past/specimen papers and mark schemes are available to download at www.cambridgeinternational.org/support (F)

12: Energy and respiration

Syllabus ref. and Key Concepts (KC)	Learning outcomes	Suggested teaching activities
12.1 Energy KC1 KC2	12.1.1 Outline the need for energy in living organisms, as illustrated by active transport, movement and anabolic reactions, such as DNA replication and protein synthesis. 12.1.2 Describe the features of ATP that make it suitable as the universal energy currency. 12.1.3 State that ATP is synthesised by: transfer of phosphate in substrate-linked reactions chemiosmosis in membranes of mitochondria and chloroplasts	Learners know from Topics 1, 2 and 6 that all living things need a source of cellular energy, obtained from mitochondria in the form of ATP, to supply their activities. Provide an activity to refresh their knowledge of this information using Paper 1 questions to host a discussion. Extend thinking by describing how ATP is a suitable molecule as the universal energy currency. (F) On the board, draw a banknote or a coin with the words ‘One ATP’ displayed on it. Discuss with learners how it is possible to think of this molecule as ‘currency’ and how ‘spending’ ATP allows cells to use the energy they store. Reinforce the idea that this ‘currency’ can be ‘spent’ on a wide range of purchases, and challenge learners to list as many biological uses of energy as they can. Examples include: cytokinesis, muscle contraction, flagellum motion, endocytosis, maintenance of body temperature, active transport and electrical discharge. After providing an example to set the scene, ask a learner for an example. Then ask another. Continue this until all members of the class have been asked for an idea. Learners convert the discussions of this lesson into a series of short, bullet-point statements. Introduce key terms, such as phosphorylation and chemiosmosis, that learners will encounter in subsequent lessons. (F)
	12.1.4 Explain the relative energy values of carbohydrates, lipids and proteins as respiratory substrates. 12.1.5 State that the respiratory quotient (RQ) is the ratio of the number of molecules of carbon dioxide produced to the number of molecules of oxygen taken in, as a result of respiration. 12.1.6 Calculate RQ values of different respiratory substrates from equations for respiration. 12.1.7 Describe and carry out investigations, using simple respirometers, to determine the RQ of germinating seeds or small invertebrates (e.g. blow fly larvae).	Learners undertake a ‘think, pair, share’ discussion to revisit their knowledge of the relative value of different components of a balanced diet in providing energy. Help learners identify fatty acids / triglycerides as the most energy-rich molecule per unit mass, due to the number of hydrogen atoms being much higher. (F) Learners carry out a practical activity in which they use a simple respirometer to calculate the respiratory quotient (RQ) of germinating seeds, or the effect of temperature on the rate of respiration of a small invertebrate. Simple designs, using a single syringe and capillary tubing are more sensitive to temperature and require minimal handling. Websites that provide guidance include: https://pbiol.rsb.org.uk/energy/gas-balance-in-respiration-and-photosynthesis/measuring-respiratory-quotient https://pbiol.rsb.org.uk/energy/gas-balance-in-respiration-and-photosynthesis/measuring-the-rate-of-metabolism. To extend thinking, challenge learners to calculate RQ values of a range of different respiratory substrates from equations for respiration. Extra information on the use of respirometers in the school laboratory: www.phschool.com/science/biology_place/labbench/lab5/features.html Learners write down three ideas they learnt in this lesson. Then ask them to share their facts in groups and to compile a master list of facts, with the most important at the top. Ask for ideas to be shared and find out which other groups agreed. To make this activity more effective and inclusive, do not choose learners on the basis of ‘hands up.’ Instead, choose learners at random. (F)