Lecture 10.pdf

Chloroplast Anatomy & Function Outer membrane: Porins in outer membrane Inner membrane: Transporters for inner membrane Stroma: – Most biochemistry – Calvin cycle, ATP synthesis, transcription, translation of chloroplastic proteins Chloroplast Anatomy & Function Thylakoid membrane: e- transport comp...

Chloroplast Anatomy & Function Outer membrane: Porins in outer membrane Inner membrane: Transporters for inner membrane Stroma: – Most biochemistry – Calvin cycle, ATP synthesis, transcription, translation of chloroplastic proteins Chloroplast Anatomy & Function Thylakoid membrane: e- transport components and ATP synthase Thylakoid space: acidified space during e- transport Loading… Plants energy storage Convert some sugars from photosynthesis into fat and starch for storage Located in chloroplast There are two stages of photosynthesis that take place in the stroma of the chloroplast. Loading… Structure of a Photosystem Located in thylakoid membrane Antenna complex: chlorophyll, carotinids and other pigments Reaction center: 2 specialized chlorophyll molecules E- transport chain in photosynthesis Cyclic Photophosphorylation: only ATP is produced in photosystem I Dark Reactions: Calvin Cycle occurs in the stroma creates glyceraldehyde-3-phosphate (a 3C sugar) Phase 1: Carbon Fixation Loading… RuBP and CO2 converted to 6 molecules of 3 phosphoglycerate (3PGA, a 3 carbon sugar) Rubisco Phase 2: Triose phosphates made (3PGA) 1 triose phosphate per 3 CO2, 9 ATP (3 ATP used later in cycle), and 6 NADPH Phase 3: RuBP is regenerated Normally RuBP fixes CO2 and 3 phosphoglycerate is produced. When O2 is fixed, the cell does photorespiration. This is NOT an efficient process. C4 plants separate steps into different locations using PEP and PEP carboxylase. CAM plants fix and then use CO2 via PEP Carboxylase at night. What are the two stages of photosynthesis and where do they occur? Loading… Where are the photosystems located? What is the role of the chlorophyll special pair? Loading… In what order are the photosystems I and II photosystem used? Photosystem Describe the pathway of the energized electrons as they leave photosystem II. What provides the energy to move protons? throught Where are the protons moved to?moved frohylakothes How is the energy of the proton motive forced used? II is used before I After being energized in Photosystem II, electrons leave the reaction center of PSII and are passed through an electron transport chain consisting of cytochrome b6f and plastocyanin. This transport chain transfers the electrons to Photosystem I. flow of elections is The energy stored in the proton gradient is used by ATP synthase to produce ATP through chemiosmosis. Protons move back into the stroma through ATP synthase, driving the synthesis of ATP from ADP and inorganic phosphate. How are the electrons that leave the reaction center of photosystem II replaced? The electrons that leave the reaction center of Photosystem II are replaced by the splitting of water molecules. This process, known as photolysis, releases oxygen, protons, and electrons, with the electrons being used to replace those lost from Photosystem II. E- transport chain in photosystem II After being energized in Photosystem I (PSI), electrons leave the reaction center of PSI and are transferred to an electron carrier called ferredoxin (Fd). Describe the pathway of the energized electrons as they leave photosystem I. What is the energy from the electrons used to do? How are the electrons that leave the photosystem I reaction center replaced? The electrons that leave the Photosystem I reaction center are replaced by the electrons that come from Photosystem II via the electron transport chain. Photosystem I E- transport chain in photosynthesis How is oxygen generated by photosynthesis? What is the ATP and the NADPH produced by the light reactions used for? T or F The Calvin cycle occurs in the thylakoid space. T or F The first step of the Calvin cycle is to fix CO2 with ribulose 1,6 bisphosphate using Rubisco. T or F The product of the Calvin cycle is sucrose. What are the triosephosphates used for? Do all plant cells do photosynthesis? Do all plant cells do cellular respiration? Normally RuBP fixes CO2 and 3 phosphoglycerate is produced. When O2 is fixed, what is made instead of the 3-phosphoglycerate (glycerate-3-phosphate)? instead of producing two molecules of 3phosphoglycerate, as in normal photosynthesis, only one molecule of 3phosphoglycerate is produced, along with one molecule of phosphoglycolate, during photorespiration. What 2 mechanisms have some plants evolved to avoid photorespiration? Structure of C4 leaf Mesophyll cells Bundle sheath cell Vascular tissue Determine if each statement is true or false. T or F Succulents are a type of CAM plant. T or F CAM plants avoid photorespiration by performing CO2 fixation only during the daytime. T or F CAM plants thrive in cool, moist environments. T or F CAM plants avoid transpiration by shutting their stomata during the day. yes RUBP (Ribulose - 1 Disphosphate) Yes , 5- RUDISCO 3- Phosphoglycerate PEP (phosphoenopyruvate) PEP Carboxylase OXaloacetate low high Masophyll Mesophyll Cells yes Yes PEP (Phosphoenolpyruvate PEP Carboxylase Oxaloacetate high and Bundle Sheath cells minimal mesophy" cells minimal -