Photosynthesis overview and pigmentsAQA A-Level Biology: Mind map

Exam questions on Photosynthesis overview and pigments

1. Cyanobacteria, algae, mosses and flowering plants all carry out photosynthesis. In every group, light is absorbed by chlorophyll, and the energy is used to make ATP by a very similar set of reactions involving membrane-bound proteins.
   Explain how the similarities in photosynthesis between these groups suggest that photoautotrophs share a common ancestor.2 marks
2. Isolated chloroplasts were kept in the dark in a buffer at pH 4 until the space inside their thylakoids also reached pH 4. They were then transferred to a buffer at pH 8 containing ADP and inorganic phosphate, still in the dark. ATP was made for a short time.
   Explain why ATP was made in this experiment even though there was no light.2 marks
3. A student separated the photosynthetic pigments from the leaves of two plants by thin-layer chromatography. The solvent front travelled 9.0 cm from the origin. The extract from a plant grown in full sun gave spots at 8.1 cm (carotene), 6.3 cm (chlorophyll a) and 5.4 cm (chlorophyll b) from the origin. The extract from a shade-tolerant plant gave the same three spots, but its chlorophyll b spot was much larger and darker.
   Calculate the Rf value of chlorophyll a in the extract from the plant grown in full sun. Show your working.3 marks