Calvin Cycle 2015 student

7.10 ATP and NADPH power sugar synthesis in the Calvin cycle The Calvin cycle makes sugar in the stroma. The necessary ingredients are – atmospheric CO 2 and – ATP and NADPH (from?) The Calvin cycle produces a three-carbon sugar called glyceraldehyde-3-phosphate (G3P). – Sugar formed from splitting glucose in glycolysis G3P is used to make glucose and other organic molecules. © 2012 Pearson Education, Inc.

Figure 7.10A Input Output: G3P Calvin Cycle CO 2 ATP NADPH

7.10 ATP and NADPH power sugar synthesis in the Calvin cycle The steps of the Calvin cycle include – carbon fixation, – reduction, – release of G3P, and – regeneration of the starting molecule ribulose bisphosphate (RuBP). © 2012 Pearson Education, Inc.

Figure 7.10B_s1 11 P P P PGA RuBP CO 2 Rubisco Input: Step Carbon fixation Calvin Cycle

Figure 7.10B_s P P P P P ATP ADP NADPH NADP  G3P 3-PGA RuBP CO 2 Rubisco Input: Step Reduction Step Carbon fixation Calvin Cycle

Figure 7.10B_s Glucose and other compounds P P P P P P P ATP ADP NADPH NADP  G3P 3-PGA RuBP CO 2 Rubisco Input: Output: Step Release of one molecule of G3P Step Reduction Step Carbon fixation Calvin Cycle

Figure 7.10B_s Glucose and other compounds P P P P P P P ATP ADP NADPH NADP  G3P 3-PGA RuBP CO 2 Rubisco Input: Output: Step Regeneration of RuBP Step Release of one molecule of G3P Step Reduction Step Carbon fixation Calvin Cycle

7.11 EVOLUTION CONNECTION: Other methods of carbon fixation have evolved in hot, dry climates C 3 plants – First product of carbon fixation is a three carbon compound 3-PGA – Close their stomata in hot dry weather (why?) – Photorespiration occurs Oxygen builds up, rubisco adds O 2 instead of CO 2 to RuBP resulting in a 2-carbon product which is broken down in the cell using ATP – What will happen if this process continues for too long? © 2012 Pearson Education, Inc.

7.11 EVOLUTION CONNECTION: Other methods of carbon fixation have evolved in hot, dry climates C 4 plants have evolved a means of – carbon fixation that saves water (closed stomata) during photosynthesis C 4 plants first fix CO 2 into a four-carbon compound. – With the help of an enzyme The four- carbon compound “shuttles” the carbon to the Calvin cycle. © 2012 Pearson Education, Inc.

Figure 7.11 Calvin Cycle Sugarcane Pineapple Mesophyll cell Bundle- sheath cell CO 2 4-C compound CO 2 3-C sugar C 4 plant 3-C sugar CAM plant Day CO 2 4-C compound Night

7.11 EVOLUTION CONNECTION: Other methods of carbon fixation have evolved in hot, dry climates CAM plants, such as pineapples and cacti. CAM plants conserve water by opening their stomata and admitting CO 2 only at night. CO 2 is fixed into a four-carbon compound, – which banks CO 2 at night and – releases it to the Calvin cycle during the day. © 2012 Pearson Education, Inc.