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BIBC102 SU.06

BIBC102 SU.06. Lecture 11 August 30, 2006 Calvin Cycle. The Dark Reactions. LNC Chapter 20, pp. 751 - 771. C 1. C 5. C 3. C 3. Fig. 20-23 (3 rd ed.). Note the carbamylated lysine side chain that is required for Mg+2 binding and creation of the active site. Fig. 20-7.

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BIBC102 SU.06

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  1. BIBC102 SU.06 Lecture 11 August 30, 2006 Calvin Cycle

  2. The Dark Reactions LNC Chapter 20, pp. 751 - 771

  3. C1 C5 C3 C3 Fig. 20-23 (3rd ed.)

  4. Note the carbamylated lysine side chain that is required for Mg+2 binding and creation of the active site Fig. 20-7

  5. Structure of ribulose 1,5 bisphosphate carboxylase “rubisco” LNC 20-5a

  6. LNC 20-5a

  7. Ribulose 1,5 bisphosphate Mg+2 carbamate LNC 20-5b

  8. 3 CO2 + 9 ATP + 6 NADPH 3-PG + 9 ADP + 6 NADP+ + 8 Pi LNC Fig. 20-14

  9. C3 + C3  C6 C6 + C3  C4 + C5 C4 + C3  C7 C7 + C3  C5 + C5 ------------------------------ 5C3  3C5

  10. Co-factor thiamine pyrophosphate Fig. 20-11a See Fig. 20-12 for detailed mechanism

  11. Transketolase reaction C6 C3 C4 C5 Fig. 20-11b

  12. Transketolase reaction C7 C3 C5 C5 Fig. 20-11c

  13. C3 + C3  C6* C6*  C6 C6 + C3  C4 + C5 C4 + C3  C7* C7*  C7 C7 + C3  C5 + C5 ------------------------------ 5C3  3C5 aldolase phosphatase trans-ketolase aldolase phosphatase trans-ketolase

  14. Fig. 20-13

  15. 3 CO2 + 9 ATP + 6 NADPH 3-PG + 9 ADP + 6 NADP+ + 8 Pi LNC Fig. 20-14

  16. Fig. 20.17

  17. LNC Fig. 20-9

  18. LNC Fig. 20-15

  19. excess excess LNC Fig. 20-16

  20. Regulation of Carbohydrate Metabolism in Plants Co-existing pathways: photosynthesis (dark reactions) triose phosphates gluconeogenesis glucose, sucrose, starch glycolysis energy production in the dark pentose shunt riboses

  21. 1. Covalent modification of rubisco 2. Light-triggered activation of several enzymes a) rise in pH and [Mg+2] in stroma as a result of proton pumping into the thylakoid lumen e.g fructose 1,6 bisphosphatase b) reduction of disulfide bonds by thioredoxin e.g. ribulose 5-P kinase sedoheptulose 1,7 bisphosphatase GAP dehydrogenease

  22. activation of Rubisco by carbamylation

  23. Fig. 20.8

  24. Ferredoxin ([Fe-S] flavoprotein- ferredoxin NADP+ oxidoreductase

  25. Regulation of four essential Calvin cycle enzymes by light: ribulose 5-phosphate kinase fructose 1,6-bisphosphatase sedoheptulose 1,7-bisphosphatase glyceraldehyde 3-phosphate dehydrogenase LNC Fig. 20-19

  26. Fig. 20.18

  27. LNC Fig. 20-26 Fructose 2,6 bisphosphate again plays a role in regulating PP-PFK-1* and FBPase-1 in the dark PFK-2 is activated, Fru 2,6 bisphosphate glycolysis is favored by PP-PFK-1 * * in plants Fru 6 P is phosphorylated by PPi not ATP (p.533)

  28. Photorespiration LNC Fig. 20-20

  29. Photorespiration chloroplast peroxisome mitochondria LNC Fig. 20-21

  30. C4 Plants LNC Fig. 20-23a

  31. Mesophyll cell Bundle-sheath cell LNC Fig. 20-23

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