Chloroplasts belong to a group of organelles called plastids. Although different types of plastid have different structures and functions, one type of plastid can change into another type of plastid in response to environmental or developmental signals. • Example 1: plants grown in the dark have plastids called etioplasts which lack chlorophyll. If these plants are exposed to light, the etioplasts quickly change into chloroplasts. • Example 2: chloroplasts in surface tissues of tomato fruits change into plastids called chromoplasts as the fruits ripen. Thylakoid membranes break down and chlorophyll synthesis stops. Chromoplasts synthesise and accumulate red lycopene and orange ẞ-carotene pigments.

1. (a)For each of these examples, explain the effect on the rate of photosynthesis of one type of plastid changing into another type of plastid. Example 1 Example 2[2]
2. (b)Outline the method you would use to separate and identify the pigments in an extract of tomato chromoplasts.[4]
3. (c)Cyanobacteria are prokaryotic organisms. Plastids are thought to have evolved from cyanobacteria that became incorporated into larger cells. Experiments show that free-living cyanobacteria can adapt to environmental signals in the same way as plastids. Fig. 2.1 shows the absorption spectra of cyanobacteria grown under two different lighting conditions. One group was grown under fluorescent light and the other group was grown under red light. The range of light wavelengths absorbed by each group of cyanobacteria was then measured under identical lighting conditions. Key: — fluorescent light - - - red light [Figure 2.1] With reference to Fig. 2.1 and the information given on pages 4 and 5, explain the effect of different lighting conditions on the absorption spectra of the two groups of cyanobacteria.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.