Exam Review - Chapter 20

20 10 net result of three turns of the calvin cycle is

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: se: overcomes inhibition by promoting ATP- dependent release of ribulose 1,5- bisphosphate, exposing the Lys amino group to nonenzymatic carbamoylation by CO2 o Activates rubisco once Mg2+ binds • 2- carboxyarabinitol 1- phosphate: inhibits carbamoylated rubisco Stage 2: Conversion of 3- Phosphoglycerate to Glyceraldehyde 3- phosphate • 3- phosphoglycerate is converted to glyceraldehyde 3- phosphate • All enzymes are located in the stroma 1st Step: 3- phosphoglycerate kinase catalyzes the transfer of a phosphoryl group from ATP to 3- phosphoglycerate to yield 1,3- bisphosphoglycerate 2nd Step: NADPH donates electrons in a reduction catalyzed by glyceraldehyde 3- phosphate dehydrogenase, producing glyceraldehyde 3- phosphate and Pi o High concentration of NADPH and ATP allow for this thermodynamically unfavorable reaction to take place o Triose phosphate isomerase: interconverts glyceraldehyde 3- phospate and dihydroxyacetone phosphate Stage 3: Regeneration of Ribulose 1,5- Bisphosphate from Triose Phosphates • Figure 20- 10 • Net result of three turns of the Calvin cycle is the conversion of three molecules of CO2 and one molecule of phosphate to a molecule of triose phosphate • 3 CO2 6 3- Phosphoglycerate 6 1,3- Bisphosphoglycerate 6 Glyceraldehyde 3- phosphate 5 glyceraldehyde 3- phosphate 3 ribulose 5- phosphate 3 ribulose 1,5- bisphosphate o Requires 9 ATP and 6 NADPH o Net 1 molecule of glyceraldehyde 3- phosphate • NADPH and ATP are produced in the light- dependent reactions of photosynthesis in the ratio of 2:3 • “Dark reactions” were named so to distinguish them from the primary light- driven reactions of electron transfer to NADP+ and synthesis of ATP Pi- triose phosphate antiport system: helps transport triose phosphate into the cytosol and Pi into the chloroplast • Helps transport ATP equivalents and reducing equivalents from the chloroplast to the cytosol • dihydroxy...
View Full Document

Ask a homework question - tutors are online