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" thatmanifest as oscillations in gene expression with a period of ~24 hours. The circadian rhythms aregoverned 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 anddephosphorylated and reproduces the 24 hour period in the absence of any light cues. In vivo in thecyanobacteria, the phosphorylation of KaiC peaks at night, and this results in the activation of genesencoding components of the oxidative pentose phosphate pathway.DaytimephotosynthesismPSI ROSKaiA KaiB KaiCNADPHCO₂ fixation andglycogen synthesis60+ATP+Mgw4872%P-KaiC24DetoxificationmechanismsFOSSOPPPZNADPH0000ROS0time (hours)Night-time oxidative pentosephosphate pathway carbon flux(a) Draw the reactions of the oxidative phase of the pentose phosphate pathway including all reactantsand products and enzymes (excluding the final isomerization step).(b) One hypothesis for why the oxidative pentose phosphate pathway is activated at night is to preparecyanobacteria for the accumulation of reactive oxygen species (ROS) generated during the day by thelight-harvesting reactions. Which product of the oxidative pentose phosphate pathway is necessary tocombat reactive oxygen species? What enzyme uses this product to combat ROS and what antioxidantdoes it generate? Which particular ROS does the antioxidant target via a specific enzyme, and what isthe 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

An alternative pathway for glucose oxidation is the pentose phosphate pathway (PPP). In…

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

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter10: Cell Division And Mitosis

Section: Chapter Questions

Problem 3TYK: A major difference between hereditary information in eukaryotes and prokaryotes is: a. in...