Scheme of Work Cambridge International as & a level

Extension activity: How was the light-independent stage first determined? Set learners the task of carrying out online research into the work of Calvin and the lollipop flask containing Chlorella algae. Extend thinking by explaining to learners that Calvin cycle intermediates are used to produce other molecules, limited to GP to produce some amino acids and TP to produce carbohydrates, lipids and amino acids.

A significant number of key terms, are introduced in this topic. To help familiarise learners with these terms, learners work in pairs to describe key words to each other, but without using other (listed) key words. For example, challenge learners to describe what happens in the light-independent reaction without using the three key terms: ATP, rubisco, and glucose. (F)

13.2 Investigation of limiting factors KC5 KC6

13.2.1 State that light intensity, carbon dioxide concentration and temperature are examples of limiting factors of photosynthesis. 13.2.2 Explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis. 13.2.3 Describe and carry out investigations using redox indicators, including DCPIP and methylene blue, and a suspension of chloroplasts to determine the effects of light intensity and light wavelength on the rate of photosynthesis. 13.2.4 Describe and carry out investigations using whole plants, including aquatic plants, to determine the effects of light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis.

Learners consider in small groups how the rate of photosynthesis can be measured. Many will recall some methods from their Cambridge IGCSE (or equivalent) studies. Options include those described in: www.saps.org.uk/secondary/teaching-resources/157-measuring-the-rate-of-photosynthesis Arrange learners into a line of four or five and ask them to pass small items (e.g. coins) from one end to the other, except for one learner who you ask to wait at least for a few seconds before passing the item on. Draw on this analogy to explain how limiting factors restrict the further increase in the rate of photosynthesis. Explain that knowledge of these factors is important in controlling the growing conditions of commercial crops, especially in protected environments.