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Match structure and function

Match structure and function. Learning Objectives. Outline how the products of the LDS are used in the LIS Explain the role of carbon dioxide in the LIS State what TP is used to make State that TP is recycled to make RuBP. Photosynthesis. Photophosphorylation :

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Match structure and function

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  1. Match structure and function

  2. Learning Objectives • Outline how the products of the LDS are used in the LIS • Explain the role of carbon dioxide in the LIS • State what TP is used to make • State that TP is recycled to make RuBP

  3. Photosynthesis Photophosphorylation: ‘The making of ATP energy using the energy from light’ May involve cyclic or non-cyclic phosphorylation Cyclic – PSI – intergranal lamellae Non – cyclic PSI & PSII – granal lamellae

  4. Non-cyclic Light excites electrons of Mg in PSII & PSI Electrons passed along electron carriers Energy released drives H+ proton pumps H+ accumulates in thylakoid space – gradient forms H+ flow down gradient through ATP synthase ATP used in light independent stage Photolysis of H20 and generation of NADPH

  5. Cyclic Only uses PSI Excited electrons are passed back to Mg in PSI No photolysis or generation of NADPH Small amounts of ATP made Used in light independent or to open stomata

  6. 1.3.4 Light independent stage Occurs in the stroma – also called the Calvin Cycle Uses ATP made in the light dependent stage CO2 becomes fixed into complex organic compounds C & O used for structure and energy store

  7. Three phases Carboxylation Carbon dioxide fixation with ribulose bisphosphate (RuBP) Reduction Reduction of glycerate 3-phosphate (GP) to glyceraldehyde 3-phosphate (GALP) Regeneration Re-formation of the CO2 acceptor molecules

  8. Rubisco Regeneration of RuBP TP

  9. RUBISCO

  10. 1.3.4 Light Independent CO2 diffuses into the stroma Combines with a 5C acceptor RuBP – uses enzyme RuBP has become carboxylated – carboxyl group Produces 2 x 3Cmolecule – glycerate 3-phosphate GP is reduced & phosphorylated to TP TP recycled by phosphorylation to RuBP

  11. 1.3.4 Light Independent stage Products of the Calvin Cycle GP used to make amino acids & fatty acids TP combines to form 6C glucose Some glucose isomerised to Fructose Fructose & glucose combine = disaccharide Some sugarspolymerised – cellulose TP converted to glycerol – makes lipids

  12. The light-independent reaction

  13. Triose phosphates (TPs) are used to form glucose. • 1C (x6) Hexose (6C) • 3C (TP) • + 6C • 3C (TP) • 5C Regenerate RuBP • `6 cycles are required to form 1 molecule of glucose • RuBP is then joined with carbon dioxide to re-start the cycle. ATP 1C (6 cycles) Hexose 5C RuBP) + 1C (CO2) 6C 2 x 3C (TP) 6C 5C Regenerate RuBP

  14. The Maths 2 molecules of GALP are made each turn 5 out of 6 molecules of GALP are used to regenerate RuBP 2 molecules of GALP are needed to make a hexose sugar How many turns are needed to make 1 molecule of hexose sugar? How many molecules of ATP and reduced NADP are needed?

  15. NADP • ADP • inorganic phosphate Products of the Calvin cycle Products of the light-independent reaction that pass back into the light-dependent reaction: Products of the light-independent reaction that are used in other processes: • triose phosphate – used to build complex carbohydrates, amino acids and lipids.

  16. How much can you remember?

  17. Summary of photosynthesis light carbohydrates, other complex molecules light- dependent reactions light- independent reactions

  18. Photosynthesis: true or false?

  19. Outlinehow light energy is converted to chemical energy (ATP and reduced NADP) in the light-dependent stage (reference should be made to cyclic and non-cyclic photophosphorylation) Explainthe role of water in the light-dependent stage. Outlinehow the products of the light-dependent stage are used in the light-independent stage (Calvin cycle) to produce triose phosphate (TP) (reference should be made to ribulosebisphosphate (RuBP), ribulosebisphosphate carboxylase (rubisco) and glycerate 3-phosphate (GP)). Explainthe role of carbon dioxide in the light-independent stage (Calvin cycle).

  20. Carbon Fixation – Light Independent Stage (Calvin Cycle) • The carbon fixation stage occurs in the stroma and results in the production of glucose. • It is a result of an enzyme controlled sequence of reactions requiring ATP and hydrogens(from reduced NADP) from the light stage, and carbon dioxide (“fixed” from the air). • It involves the reduction of carbon dioxide, that is the addition of hydrogen (from reduced NADP), to form carbohydrate. • CO2 is accepted by the 5C compound ribulose 1,5-biphosphate (RuBP) to form an unstable 6C compound. • The 6C compound formed immediately splits into two molecules of a 3C compound called glycerate 3-phosphate (GP). • ATP and reduced NADP is used to convert the two GP molecules into two molecules of triose phosphate (TP), a 3 carbon compound. • TP’s are used in the formation of carbohydrate (glucose) and to regenerate RuBP • ATP is required to regenerate RuBP

  21. Examination Questions – Model Answers 1 ATP Reduced NADP / NADPH / NADPH2 / NADPH + H+ Regenerates / produces, ribulose bisphosphate / RuBP So cycle can continue / for (further) CO2 fixation / to combine with CO2 Formation of , sugar / glucose / hexose / sucrose / starch / cellulose Formation of fat / triglyceride / lipid fatty acids / glycerol / amino acids / protein / nucleic acids / nucleotides Most triose phosphate used to produce RuBP and the rest for production of hexose

  22. Oxygen used and CO2 produced / excreted Light energy required Uses Rubisco Involves calvin cycle Reduces rate of photosynthesis / increases rate of photorespiration Less Rubisco available for CO2 / more oxygen competing with CO2 for Rubisco More O2 binding to Rubisco O2 outcompetes CO2 for Rubisco Less CO2 fixation / for Calvin cycle CO2 given off Less GP / TP, produced Less RuBP, regenerated O2, not a substrate for / cannot bind to / will not compete for. PEP carboxylase PEP carboxylase, is only specific to CO2

  23. 2 • A • D • A

  24. Flattened membrane bound sacs Termed thylakoids Arranged as stacks / grana Contain pigment / chlorophyll arranged in photosystems / quantosomes, in membrane Answer 38.5 % (62.4 / 162) x 100

  25. Different lighting has little effect Variation in percentage less than 3 Probably not significant Yield is less for low pressure sodium lamps The best yield is metal halide Crops can be grown out of season /all year round Plants photosynthesize 24 hours a day Less physical damage from weather /animals Pest control easier Other factors can be controlled – e.g. Temperature, CO2, water supply, humidity

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