Lecture 9

  1. Synonyms for photorespiration
    C2 cycle

    Glycolate Pathway

    Photosynthetic carbon oxidation cycle
  2. Photorespiratory conditions
    • .035% CO2
    • 21% Oxygen
  3. Photorespiratory mutants
    Mutant can be considerably less fit for survival with decelerated growth.
  4. How can mutants grow normally like wildtypes?
    Suppression of photorespiration by increasing CO2 levels from .035% to .1-.3% (increase by almost 100 fold)
  5. 3 organelles involved in photorespiration
    Peroxisome (w/ catalase crystal), mitochondrion, and chloroplast.
  6. Glycolate-Glycerate Translocator
    Interaction between chloroplast and peroxisome where GLYCERATE is sent to chloroplast and 2 GLYCOLATE is sent to peroxisome.

    • Glycerate used for R15BP synthesis.
    • Glycolate used for a-ketoglutarate.
  7. Glycolate is converted to __________ in peroxisome

    2-phosphoglycolate -[phosphoglycolate phosphatase]-> glycolate + P

    Glycolate + O2 -[glycolate oxidase]-> Glyoxylate + H2O2

    *H2O2 -[catalase]-> (1/2)O2 + H2O

    Glyoxylate -[A or B]-> Glycine

    • A = Glutamate-glyoxylate aminotransferase; a-ketoglutarate
    • B = Serine-glyoxylate aminotransferase; hydroxypyruvate
  8. Peroxisome-Mitochondrium amino acid translocator
    Serine (from mitochondrium) sent to peroxisome as 2 glycine (from peroxisome) sent to mitochondrium.

    2 glycine used to generate NADH, CO2, NH4, and serine.
  9. 2 glycine are _______ in the mitochondria to yield _____
    Oxidized, serine

    2 Glycine -[Glycine decarboxylase-serine hydroxymethyl transferase complex]-> Serine

    CO2, NH4, NADH formed
  10. GDC-SHMT
    Glycine decarboxylase-serine hydroxymethyl transferase
  11. Ammonia released from mitochondrion is ________
    assimilated in the chloroplast
  12. Serine Peroxisome-chloroplast interaction
    Serine -[Serine glyoxylate aminotransferase]-> Hydroxypyruvate

    Hydroxypyruvate -[hydroxypyruvate reductase; NADH]-> D-glycerate


    D-glycerate -[Glycerate kinase; ATP]-> 3-Phosphoglycerate

    ~Calvin Cycle~
  13. How does peroxisome get NADH for reduction of hydroxypyruvate to glycerate
    Malate produced by chloroplast and mitochondrium is sent to the cytosol by the malate-oxaloacetate shuttle where it is turned to oxaloacetate and produces NADH
  14. Possible biological functions of photorespiration
    • 1. Help salvage carbon lost during rubisco oxygenase reaction
    • tic
    • 2. Protective function when dissipation of photosynthetic energy (ATP and reductant) is required.
Card Set
Lecture 9
Rubisco: Biochemistry and Photorespiration