Light-independent reactions and the Calvin cycleEdexcel International A Level Biology: Flashcards
What these 14 flashcards ask
- Where in the chloroplast do the light-independent reactions occur?
- What is carbon fixation?
- What is RuBP?
- Which enzyme catalyses the combination of CO₂ and RuBP?
- What happens to the six-carbon compound formed when CO₂ combines with RuBP?
- What does GP stand for and how many carbons has it?
- What is GP reduced to, and what is needed?
- What is the role of ATP in the Calvin cycle?
- What is the role of reduced NADP in the Calvin cycle?
- How many ATP and reduced NADP are used per CO₂ fixed?
- What fraction of GALP leaves the cycle?
- Name four types of molecule made from the products of the Calvin cycle.
- What happens to GP and RuBP when light is switched off?
- What happens to GP and RuBP when CO₂ falls?
Exam questions on Light-independent reactions and the Calvin cycle
- A student isolates intact chloroplasts from spinach leaves and suspends them in a buffer containing hydrogencarbonate ions, which act as a source of carbon dioxide. In the light, the chloroplasts take up carbon dioxide and make GALP.Explain why isolated chloroplasts kept in the dark in this buffer cannot make GALP, even though carbon dioxide is available.2 marks
- A plant biochemist is calculating the energy requirements of the Calvin cycle in a leaf. She assumes that, for every carbon dioxide molecule fixed, the cycle uses 3 molecules of ATP and 2 molecules of reduced NADP.Explain why most of the GALP made in the Calvin cycle is not used to make carbohydrate but is used in another process.2 marks
- Tomato plants grown in a glasshouse are supplied with carbon dioxide containing radioactive ¹⁴C for a short time. Later, radioactivity is found in the starch in the leaves, the cellulose in the cell walls, the proteins in the fruits and the lipids in the seeds.Describe how carbon from carbon dioxide is incorporated into GALP in the Calvin cycle.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).