{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Exam Review - Chapter 20

Oxygenase reaction results in no fixation of carbon

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: acetone phosphate is formed in the stroma and transported to the cytosol o converted to 3- phosphoglycearte and generates ATP and NADH Reductive assimilation of CO2 requires ATP and NADPH • several stromal enzymes have evolved to take advantage of light- induced contions, which signal the availability of ATP and NADPH o enzymes are more active in an alkaline environment and at high [Mg2+) • Certain enzymes are activated by light- driven reduction of disulfide bonds between two Cys residues that are critical to their activities o When these Cys residues are oxidized, they are inactive, normal when it is dark o With illumination, electrons flow from photosystem I to ferredoxin, which passes electrons to thioredoxin, which is catalyzed by ferredoxin- thioredoxin reductase o Thioredoxin donates electrons to the disulfide bonds of light- activated ezymes • At night, the Cys residues are reoxidized and inactivated 20.2: Photorespiration and the C4 and CAM Pathways • Photosynthetic cells produce O2 during the light- driven reactions and use CO2 during the light- independent processes • In the dark, plants carry out mitochondrial respiration, oxidation of substrates to CO2 and the conversion of O2 to H2O • Photorespiration: costly side reaction of photosynthesis • Rubisco is not absolutely specific for CO2 as a substrate O2 competes with CO2 at the active site o Rubisco can catalyze the condensation of O2 with ribulose 1,5- bisphosphate to form 3- phosphoglycerate and 2- phosphoglycolate, a useless product • The oxygenase reaction results in no fixation of carbon and is a net liability to the...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online