Photosynthesis: Light-Independent Stage

Building Sugars What products came from the light-dependent reactions? ATP and NADPH Light-independent reactions use ATP and NADPH to build sugars from CO2 ATP energy source NADPH high energy electrons and H+ Where do these reactions happen? Stroma of the chloroplasts Who mapped it out? Melvin Calvin (called Calvin Cycle)

The Calvin Cycle: Part 1 Where do we also find GP? CO2+ATP+NADPHADP+Pi+NADP++glyceraldehyde-3-phosphate(GP) Where do we also find GP? Half-way point in glycolysis Can start glycolysis from here Phase 1: Carbon Fixation CO2 is fixed to 1,5-bisphosphate (RuBP) by the enzyme RuBP carboxylase/oxygenase (rubisco) creating a 6-C sugar 6-C is broken into two 3-phosphateglycerates (PGA)

The Calvin Cycle: Part 2 Phase 2: Reduction 3) NADPH and ATP supply the energy, electrons, and H+ needed to change PGA into GP How many GP do we have? 2 How many do we need to make glucose? Why do plants NOT just make sugar with the 2 GP? Need to regenerate RuBP or cycle shuts down Where have we seen this before? Oxaloacetate in the Krebs cycle

The Calvin Cycle: Part 3 Phase 3: Regeneration 4) GP molecules will be used to build RuBP molecules 3 turns of the cycle will produce 6 GP but 5 will be used to place the RuBP used; the left over G3P is used to build sugars 3 Turns: - 3 CO2 and 3 RuBP (5-C)  18 C - 6 GPs produced - 5 GPs 15 C 3 RuBP - Last GP builds a sugar How many turns are needed to make glucose? 6! That is really complex How many ATP are used to make glucose? 18 ATP (3 ATP/Turn; 6 Turns)

Calvin Cycle: Regulation What is used to regulate the cycle? ATP and NADPH levels What enzyme do they effect? Rubisco Rubisco is found in all photosynthetic organisms and up to 50% of all proteins in a leaf; most abundant protein on Earth (6kg/person) What does the name RuBP carboxylase/oxygenase tell you about the enzyme? Reacts with both CO2 and O2 Competitively inhibit each other

The Problem with Gas Exchange How does CO2 and O2 get in and out of a plant? Stromata under the leaves What else can escape through a stromata that the plant needs? H2O What problems must plants in dry, hot climates deal with? The plant needs to take in CO2 and release O2, but the open stromata will also release H2O H2O out

Homework Read Ch 10 and do Ch 10 vocabulary Do Ch 9 vocabulary “Test Your knowledge” for Ch 9 and “Apply Evolutionary Thinking” Lab reports due next Thursday Ch 10 and 11 are left and then a test on Ch 9, 10 and 11