Plant Respiration Releases 50% of fixed CO 2 Provides energy for all sinks,

1. Plant Respiration Releases 50% of fixed CO2 Provides energy for all sinks, source leaves at night & helps source during day!

2. Plant Respiration Similar, but more complex than in animals Making precursors, recycling products, releasing energy are also important

3. Plant Respiration Glycolysis in cytosol Pyruvate oxidation in mito Krebs cycle in mito Electron transport & chemiosmosis in mito

4. Plant Respiration • Glycolysis in cytosol • 1 glucose -> 2 pyruvate • Yields 2 NADH & 2 ATP per glucose Unique features in plants • May start with DHAP from cp instead of glucose

5. Unique features in plants • May start with DHAP from cp instead of glucose • May yield malate cf pyr • PEP ->OAA by PEPC, then reduced to malate

6. Plant Respiration • May yield malate cf pyr • PEP ->OAA by PEPC, then reduced to malate • Get more ATP/NADH in mito

7. Unique features in plants • May yield malate cf pyr • PEP ->OAA by PEPC, then reduced to malate • Get more ATP/NADH in mito • Replaces substrates

8. Plant Respiration • Glycolysis in cytosol • 1 glucose -> 2 pyruvate • Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH

9. Plant Respiration • Glycolysis in cytosol • 1 glucose -> 2 pyruvate • Yields 2 NADH & 2 ATP per glucose Anaerobic plants ferment pyr to regenerate NAD+ Form EtOH Less toxic than lactate because diffuses away

10. Plant Respiration • Krebs cycle • Similar, but more complex Key role is making intermediates & recycling products

11. Plant Respiration • Krebs cycle • Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn

12. Plant Respiration • Krebs cycle • Similar, but more complex Key role is making intermediates & recycling products Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis

13. Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going

14. Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going

15. Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources

16. Plant Respiration Many ways to feed in other substrates to burn or replace intermediates used for biosynthesis Needed to keep cycle going Malic enzyme is key: lets cell burn malate or citrate from other sources PEPCarboxylase lets cell replace Krebs intermediates used for synthesis

17. Plant Respiration Pentose phosphate shunt in cytosol orcp • 6 glucose-6P + 12NADP++ 7 H2O -> 5 glucose-6P + 6 CO2 + 12 NADPH +12 H+ : makes NADPH & intermediates

18. Plant Respiration Pentose phosphate shunt in cytosol orcp makes NADPH & intermediates Uses many Calvin Cycle enzymes

19. Plant Respiration Pentose phosphate shunt in cytosol orcp makes NADPH & intermediates Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors

20. Plant Respiration Uses many Calvin Cycle enzymes Makes nucleotide & phenolic precursors Gets Calvin cycle started at dawn

21. ATP generation 2 stages 1) e- transport 2) chemiosmotic ATP synthesis

22. Three steps transport H+ across membrane 1) NADH dehydrogenase pumps 4 H+/ 2 e- 2) Cyt bc1 pumps 4 H+/ 2 e- 3) Cyt c oxidase pumps 2 H+/ 2 e- and adds 2 H+ to O to form H2O

23. e- transport • Plants have additional enzymes! • NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+

24. Additional e- transport enzymes! • NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone

25. Additional e- transport enzymes! • NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone • Helps burn off excess NADH from making precursors

26. Additional e- transport enzymes! • NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone • Helps burn off excess NADH from making precursors • Much lower affinity for NADH than complex I

27. Additional e- transport enzymes! • NADH dehydrogenase in matrix that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone • Helps burn off excess NADH from making precursors • Energy is released as heat • NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+

28. Additional e- transport enzymes! • NADH dehydrogenase in intermembrane space that transfers e- from NADH to UQ w/o pumping H+ Insensitive to rotenone • "imports" e- from cytoplasmic NADH • Much lower affinity for NADH than complex I • Energy is released as heat

29. Additional e- transport enzymes! • NADPH dehydrogenase in intermembrane space that transfers e- from NADPH to UQ w/o pumping H+ Insensitive to rotenone • "imports" e- from cytoplasmic NADPH

30. Additional e- transport enzymes! • Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ • Insensitive to Cyanide, Azide • or CO • Sensitive to SHAM • (salicylhydroxamic acid)

31. Additional e- transport enzymes! • Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ • Insensitive to Cyanide, Azide or CO • Sensitive to SHAM (salicylhydroxamic acid,) • Also found in fungi, trypanosomes & Plasmodium

32. Additional e- transport enzymes! • Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ • Also found in fungi, trypanosomes & Plasmodium • Energy lost as heat: • can raise Voodoo lilies • 25˚ C

33. Additional e- transport enzymes! • Alternative oxidase on matrix side of IM transfers e- from UQ to O2 w/o pumping H+ • Plants also have an uncoupler protein: lets H+ in w/o doing work!

34. Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency? Additional e- transport enzymes! Why so many ways to reduce ATP synthesis efficiency?

35. Additional e- transport enzymes! • Why so many ways to reduce ATP synthesis efficiency? • Regenerate NAD+ needed for precursor synthesis • Generate heat • Burn off excess energy captured by photosynthesis • Prevalence says they're doing something important! • Additional e- transport enzymes! • Why so many ways to reduce ATP synthesis efficiency? • Regenerate NAD+ needed for precursor synthesis • Generate heat • Burn off excess energy captured by photosynthesis • Prevalence says they're doing something important!

36. Regulating Respiration Regulated by demand for ATP, NADPH and substrates

37. Glycolysis is allosterically regulated at 3 irreversible steps Hexokinase is allosterically inhibited by its product: G-6P Allosteric site has lower affinity than active site

38. Glycolysis is allosterically regulated at 3 irreversible steps Hexokinase is allosterically inhibited by its product: G-6P Pyr kinase is allosterically inhibited by ATP & citrate

39. Regulating Glycolysis • Main regulatory step is Phosphofructokinase • Rate-limiting step • Committed step

40. Regulating Glycolysis • Main regulatory step is • Phosphofructokinase • Inhibited by Citrate, PEP & ATP • Stimulated by • ADP

41. Regulating Pyruvate DH • Mainly by a kinase • Inhibited when Pi added

42. Regulating Pyruvate DH • Mainly by a kinase • Inhibited when Pi added • NADH, Acetyl CoA, ATP • NH4+ inhibit PDH & • activate kinase

43. Regulating Pyruvate DH • Mainly by a kinase • Inhibited when Pi added • NADH, Acetyl CoA, ATP • NH4+ inhibit PDH & • activate kinase • Activated when no Pi • ADP, pyruvate inhibit • kinase

44. REGULATING THE KREBS CYCLE Krebs cycle is allosterically regulated at 4 enzymes citrate synthase Isocitrate dehydrogenase 3) a-ketoglutarate dehydrogenase 4) Malate dehydrogenase

45. REGULATING THE KREBS CYCLE Krebs cycle is allosterically regulated at 4 enzymes citrate synthase Isocitrate dehydrogenase 3) a-ketoglutarate dehydrogenase 4) Malate dehydrogenase All are inhibited by NADH & products

46. Environmental factors • Temperature • Rate ~ doubles for each 10˚ C increase up to ~ 40˚ • At higher T start to denature

47. Environmental factors • Temperature • Rate ~ doubles for each 10˚ C increase up to ~ 40˚ • At higher T start to denature 2) pO2 • Respiration declines if pO2 <5%

48. Environmental factors • Temperature • Rate ~ doubles for each 10˚ C increase up to ~ 40˚ • At higher T start to denature 2) pO2 • Respiration declines if pO2 <5% • Problem for flooded roots

49. Environmental factors • Temperature • Rate ~ doubles for each 10˚ C increase up to ~ 40˚ • At higher T start to denature 2) pO2 • Respiration declines if pO2 <5% • Problem for flooded roots • pCO2 • Inhibits respiration at 3%

50. Environmental factors • Temperature • Rate ~ doubles for each 10˚ C increase up to ~ 40˚ • At higher T start to denature 2) pO2 • Respiration declines if pO2 <5% • Problem for flooded roots • pCO2 • Inhibits respiration at 3% • No obvious effects at 700 ppm, yet biomass reduced