For the entire process of photosynthesis: 6 CO 2 + 18 ATP + 12 NADPH + 12 H 2 O C 6 H 12 O 6 + 18 ADP + 18 Pi + 12 NADP+ 6 O 2 + 6 H 2 O + 12 H+
•What is photorespiration?•When does this occur?
Fig. 10-19a Stoma C 4 leaf anatomy Photosynthetic cells of C 4 plant leaf Vein (vascular tissue) Bundle- sheath cell Mesophyll cell Calvin cycle: chloroplast of bundle sheath cells C4 and CAM adaptations
Fig. 10-19b Sugar CO 2 Bundle- sheath cell ATP ADP Oxaloacetate (4C) PEP (3C) PEP carboxylase Malate (4C) Mesophyll cell CO 2 Calvin Cycle Pyruvate (3C) Vascular tissue The C 4 pathway
Fig. 10-20 CO 2 Sugarcane Mesophyll cell CO 2 C 4 Bundle- sheath cell Organic acids release CO 2 to Calvin cycle CO 2 incorporated into four-carbon organic acids (carbon fixation) Pineapple Night Day CAM Sugar Sugar Calvin Cycle Calvin Cycle Organic acid Organic acid (a) Spatial separation of steps (b) Temporal separation of steps CO 2 CO 2 1 2
The Importance of Photosynthesis: A Review Light reactions: • Are carried out by molecules in the thylakoid membranes • Convert light energy to the chemical energy of ATP and NADPH • Split H 2 O and release O 2 to the atmosphere Calvin cycle reactions: • Take place in the stroma • Use ATP and NADPH to convert CO 2 to the sugar G3P • Return ADP, inorganic phosphate, and NADP+ to the light reactions O 2 CO 2 H 2 O Light Light reaction Calvin cycle NADP + ADP ATP NADPH + P 1 RuBP 3-Phosphoglycerate Amino acids Fatty acids Starch (storage) Sucrose (export) G3P Photosystem II Electron transport chain Photosystem I Chloroplast Figure 10.21
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