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PSI ROS phosphorylated and repr es the 24 hol period in the absence of any light cues. In VIVO in the anobacteria, the phosphorylation of Kaic peaks at night, and this results in the activation of genes coding components of the oxidative pentose phosphate pathway. Daytime photosynthesis KaiA KaiB Kaic NADPH 80 ROS 3 co, fixation and glycogen synthesis +ATP 60 +Mg Detoxification mechanisms 40 20- OPPP NADPH 48 o00 24 72 time (hours) Night-time oxidative pentose phosphate pathway carbon flux O Draw the reactions of the oxidative phase of the pentose phosphate pathway including all reactants d products and enzymes (excluding the final isomerization step). O One hypothesis for why the oxidative pentose phosphate pathway is activated at night is to prepare anobacteria for the accumulation of reactive oxygen species (ROS) generated during the day by the ht-harvesting reactions. Which product of the oxidative pentose phosphate pathway is necessary to mbat reactive oxygen species? What enzyme uses this product to combat ROS and what antioxidant es it generate? Which particular ROS does the antioxidant target via a specific enzyme, and what is e enzyme? What other product does the oxidative pentose phosphate pathway produce, what is it used for, d what daytime activity might production of this product prepare cynobacteria, for? %P-KaiC

PSI ROS phosphorylated and repr es the 24 hol period in the absence of any light cues. In VIVO in the anobacteria, the phosphorylation of Kaic peaks at night, and this results in the activation of genes coding components of the oxidative pentose phosphate pathway. Daytime photosynthesis KaiA KaiB Kaic NADPH 80 ROS 3 co, fixation and glycogen synthesis +ATP 60 +Mg Detoxification mechanisms 40 20- OPPP NADPH 48 o00 24 72 time (hours) Night-time oxidative pentose phosphate pathway carbon flux O Draw the reactions of the oxidative phase of the pentose phosphate pathway including all reactants d products and enzymes (excluding the final isomerization step). O One hypothesis for why the oxidative pentose phosphate pathway is activated at night is to prepare anobacteria for the accumulation of reactive oxygen species (ROS) generated during the day by the ht-harvesting reactions. Which product of the oxidative pentose phosphate pathway is necessary to mbat reactive oxygen species? What enzyme uses this product to combat ROS and what antioxidant es it generate? Which particular ROS does the antioxidant target via a specific enzyme, and what is e enzyme? What other product does the oxidative pentose phosphate pathway produce, what is it used for, d what daytime activity might production of this product prepare cynobacteria, for? %P-KaiC

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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2. Cyanobacteria are photosynthetic prokaryotes that are likely responsible for generating the oxygen- rich atmosphere we enjoy on Earth. Many species of cyanobacteria display "circadian rhythms" that manifest as oscillations in gene expression with a period of ~24 hours. The circadian rhythms are governed by a biochemical cascade that regulates the phosphorylation of a single protein. Remarkably, this circadian "clock" can be reconstituted in vitro with only 3 proteins, known as KaiA, KaiB and Kaic. Upon addition of Mg2+ and ATP to the reaction, KaiC cycles between being phosphorylated and dephosphorylated and reproduces the 24 hour period in the absence of any light cues. In vivo in the cyanobacteria, the phosphorylation of KaiC peaks at night, and this results in the activation of genes encoding components of the oxidative pentose phosphate pathway. Daytime photosynthesis m PSI ROS KaiA KaiB KaiC NADPH CO₂ fixation and glycogen synthesis 60 +ATP +Mg w 48 72 %P-KaiC 24 Detoxification mechanisms FOSS OPPP Z NADPH 0000 ROS 0 time (hours) Night-time oxidative pentose phosphate pathway carbon flux (a) Draw the reactions of the oxidative phase of the pentose phosphate pathway including all reactants and products and enzymes (excluding the final isomerization step). (b) One hypothesis for why the oxidative pentose phosphate pathway is activated at night is to prepare cyanobacteria for the accumulation of reactive oxygen species (ROS) generated during the day by the light-harvesting reactions. Which product of the oxidative pentose phosphate pathway is necessary to combat reactive oxygen species? What enzyme uses this product to combat ROS and what antioxidant does it generate? Which particular ROS does the antioxidant target via a specific enzyme, and what is the enzyme? (c) What other product does the oxidative pentose phosphate pathway produce, what is it used for, and what daytime activity might production of this product prepare cynobacteria for? 0x80000
Transcribed Image Text:2. Cyanobacteria are photosynthetic prokaryotes that are likely responsible for generating the oxygen- rich atmosphere we enjoy on Earth. Many species of cyanobacteria display "circadian rhythms" that manifest as oscillations in gene expression with a period of ~24 hours. The circadian rhythms are governed by a biochemical cascade that regulates the phosphorylation of a single protein. Remarkably, this circadian "clock" can be reconstituted in vitro with only 3 proteins, known as KaiA, KaiB and Kaic. Upon addition of Mg2+ and ATP to the reaction, KaiC cycles between being phosphorylated and dephosphorylated and reproduces the 24 hour period in the absence of any light cues. In vivo in the cyanobacteria, the phosphorylation of KaiC peaks at night, and this results in the activation of genes encoding components of the oxidative pentose phosphate pathway. Daytime photosynthesis m PSI ROS KaiA KaiB KaiC NADPH CO₂ fixation and glycogen synthesis 60 +ATP +Mg w 48 72 %P-KaiC 24 Detoxification mechanisms FOSS OPPP Z NADPH 0000 ROS 0 time (hours) Night-time oxidative pentose phosphate pathway carbon flux (a) Draw the reactions of the oxidative phase of the pentose phosphate pathway including all reactants and products and enzymes (excluding the final isomerization step). (b) One hypothesis for why the oxidative pentose phosphate pathway is activated at night is to prepare cyanobacteria for the accumulation of reactive oxygen species (ROS) generated during the day by the light-harvesting reactions. Which product of the oxidative pentose phosphate pathway is necessary to combat reactive oxygen species? What enzyme uses this product to combat ROS and what antioxidant does it generate? Which particular ROS does the antioxidant target via a specific enzyme, and what is the enzyme? (c) What other product does the oxidative pentose phosphate pathway produce, what is it used for, and what daytime activity might production of this product prepare cynobacteria for? 0x80000
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