Photosynthesis, food production and turbo-charging

1. Photosynthesis, food production and turbo-charging Kate Andrews Lorraine Bruce Kath Crawford Marjorie Smith

2. Sustainability and Interdependence • Food production is an area of vital importance for biological research. An understanding of photosynthesis lies at its core. • Studies should focus on the energy-gathering process and the transfer of high-energy electrons through an electron transfer chain to generate ATP. • The action of Rubisco as part of the Calvin cycle should be included as this is the carbohydrate-forming stage.

3. Sustainability and Interdependence • Through the use of selection, inbreeding, outbreeding and crossbreeding, as well as the use of genetic and reproductive technology, new strains and varieties are generated for production. • Responsible citizens should understand the importance of maintaining biodiversity while protecting crops and maintaining the genetic resources for plant and animal breeding.

4. Unit 3 Sustainability and Interdependence • 1 The science of food production • Food supply. • (i) Food security and sustainable food production. • Increase in human population and concern for food security leads to a demand for increased food production. • Food production must be sustainable and not degrade the natural resources on which agriculture depends.

5. Unit 3 Sustainability and Interdependence • (b) Plant growth and productivity • Photosynthesis • Absorbed energy excites electrons in the pigment molecule. Transfer of these high-energy electrons through electron transport chains releases energy to generate ATP by ATP synthase. • Energy is also used for photolysis, in which water is split into oxygen, which is evolved, and hydrogen, which is transferred to the coenzymeNADP+

6. Prior learning • The overall equation for photosynthesis and how this compares with the overall equation for aerobic respiration. • The principle of limiting factors. • The differentiation of organelles within eukaryotic cells. • The role of ATP in the transfer of energy. • Metabolic pathways as integrated and controlled pathways of enzyme-catalysed reactions within cells.

7. Learners will be familiar with this sort of thing -

8. Absorption of carbon dioxide

9. Production of oxygen

10. Production of starch

11. Photosynthesis conversion of light energy into chemical energy light energy 6CO2 + 6H2O  C6H12O6 + 6O2 6CO2 + 6H2O C6H12O6 + 6O2 energy Respiration

12. Unit 1, Cell Biology Photosynthesis Chemistry of photosynthesis, as a series of enzyme-controlled reactions, in a two-stage process Light reactions: the light energy from the sun is trapped by chlorophyll in the chloroplasts and is converted into chemical energy in the form of ATP. Water is split to produce hydrogen and oxygen. Excess oxygen diffuses from the cell. Carbon fixation: hydrogen and ATP produced by the light reaction is used with carbon dioxide to produce carbohydrate.

13. …..and perhaps from Nat 5 this sort of thing…… Carbon fixation H20

14. Sometimes called the photolysis of water, the overall effect of the Hill reaction is to split water into oxygen, which is evolved, and hydrogen whichreduces NADP+ to NADPH 2H20 + 2A 2AH2 + O2 ‘A’ is an artificial electron acceptor, for example - 2,6-dichlorophenol-indophenol (DCPIP) which is blue in its oxidised form and colourless when it is reduced (DCPIPH2). DCPIP + 2H+ + 2e-DCPIPH2

15. Demonstrating the Hill reaction • It is essential that all solutions, tubes, and other equipment are chilled beforehand and kept in melting ice until the DCPIP reduction stage.

16. * Add DCPIP to tube 5 after heating buffer and chloroplast mixture

17. Energy capture by photosynthetic pigments to generate ATP and for photolysis. Absorption spectra of Chlorophyll a and b and carotenoids compared to the action spectra for photosynthesis. Carotenoids extend the range of wavelengths absorbed by photosynthesis and pass the energy to chlorophyll. Examination of spectrum of visible light and artificial light sources with a simple spectroscope. Examine light transmission through extracted chlorophyll with a simple spectroscope. Investigate the action spectra of photosynthesis in plants using coloured filters. Chromatography of photosynthetic pigments. Research photosynthetic pigments in other photoautotrophs.

19. *Add DCPIP to tube 5 after heating buffer and chloroplast suspension mixture. **Heat tube 5 before adding chloroplast suspension to tubes 1, 2 and 4.

20. What we can deduce from our ‘Hill reaction’: Isolated chloroplasts are necessary to produce the reducing agent which causes DCPIP to lose its colour. Light is essential for this to happen.

21. Hill showed that... • oxygen evolution could occur without reduction of carbon dioxide, providing evidence for the splitting of water. • chloroplasts could carry out a light-driven reduction of an electron acceptor during the light-dependent reactions. • the light reactions of photosynthesis are entirely located in the chloroplast. • It was later shown that NADP+ is the electron acceptor in chloroplasts

22. Light reactions of photosynthesis • Light absorption by chlorophyll and other pigments • High energy electrons are transferred through an • electron transfer chain generating ATP • Energy is also used to split water (photolysis) into • oxygen which is released and hydrogen • which is accepted by NADP+ to form NADPH

23. Carbon fixation – the Calvin cycle Carbon is fixed when carbon dioxide enters the Calvin cycle by attaching to ribulose bisphosphate (RuBP). The enzyme that catalyses this reaction is rubisco. ATP and NADPH generated by the light reactions provide energy and hydrogen for the synthesis of carbohydrate.

24. ......and where do the reactions occur?

26. Thylakoid membrane • chlorophyll • light-harvesting • electron transfer • O2 evolution • ATP production • Stroma • Rubisco • CO2 fixation • sugar and starch • synthesis • http://www.saps.org.uk/ Pea chloroplast

27. Skills addressed • planning and designing investigations/experiments. • safely carrying out investigations/experiments and recording detailed observations and collecting data • drawing valid conclusions and giving explanations supported by evidence/justification • evaluating investigations/experiments and suggesting improvements

28. Photosynthesis..........Turbo-charging (b) Plant growth and productivity(i) Photosynthesis (cont) The enzyme RuBisCO fixes carbon dioxide by attaching it to ribulosebisphosphate (RuBP) in the Calvin cycle. The intermediate produced is phosphorylated by ATP and combined with hydrogen from NADPH to form glyceraldehyde-3-phosphate (G3P). G3P is used to regenerate RuBP and for the synthesis of sugars. (c) Plant and animal breeding by manipulation of heredity for improved plant crops, improved animal stock, to support sustainable food production. (i) Plant field trials are carried out in a range of environments to compare the performance of different cultivars or treatments and to evaluate GM crops

29. Turbo-charged Rice ‘As the world population races toward 10 billion, agricultural scientists are realizing that another “green revolution” is needed for crop yields to meet demands for food. In rice, yield potential is limited by photosynthesis’ C4Rice Project This project is attempting to make rice much better at photosynthesis!

32. NEW POTATOES

33. 1) Golden rice 2) GM crops as food aid 3) Less toxic oil seed rape 4) New potatoes 5) Turbocharged rice

35. The assignment • investigation stage: • select an appropriate biology topic… • investigate/research the topic, focusing on applications and impact on society/the environment • process the information/data collected • controlled assessment stage: • knowledge and understanding • application • balanced evaluation • reasoned conclusion