Energy Capturing Pathways (Photosynthesis) I. Introduction A. History

1. van Helmont,1630, showed plants need Water 2. Priestly, 1772, showed plants need Gas (phlogiston) 3. Ingenhaus, 1779, showed plants need Sunlight 4. de Saussure, 1804, showed Organized all the pieces the hydrogen in the glucose comes from splitting water 5. Van Neil, 1930, showed Page 98

B. Photosynthesis Overview Figure 6.3

& Autotrophs (self feeders) are organisms that can fix energy into carbon molecules. Figure 6.1

C. Background Information 1. Photosynthetic Structures Figure 6.2 Figure 6.2

2. Light Properties Figure 6.4

3. Pigments Magnesium a. Chlorophylls are primary and reflect greens. b. Xanthophylls are secondary and reflect reds. c. Carotenoids are secondary and reflect oranges and protect chlorophylls. Figure 6.5

II. Light Dependent Reactions A. Where located? The light dependent reactions occur via chlorophyll pigments in the thylakoid membrane of chloroplasts. Why is this solution red?

B. Steps (Light Dependent Reactions) Figure 6.6 Making ATP & NADPH using sunlight Figure 6.7

Actual written steps 1. Light excites electrons of magnesium of the chlorophyll molecules of photo-system II and I. 2. Electrons from II are passed through an ETC to make ATP, while electrons from I are passed through an ETC to make NADPH. 3. Electrons from II are used to backfill I chlorophyll that lost electrons to NADPH. 4. Water is split by II to fill electrons lost to I by stealing electrons from hydrogen. 5. Repeat as long as you have enough ????

Do plants need to keep expelling O2 for their benefit? C. Outcomes 1. The ATP and NADPH  sent to chloroplast stroma and are used to energize CO2 (via ATP) & add hydrogen (via NADPH). 2. The O2 sent to the stomata to be expelled or to the mitochondria for use. Do plants need to keep expelling O2 for their benefit? Or yours?

III. Light Independent Reactions A. Where located? The eight step process (Calvin cycle, the light independent reactions, or the DARK reactions) is in the chloroplast’s stroma. Figure 6.3

B. Steps (Light InDependent Reactions) Adding versus Rearranging Figure 6.8

Actual written steps 1. Rubisco attaches 3CO2 to RuBP. 2. Requires 6ATP and 6NADPH to make 6G3P. 3. Separate 1G3P and hold in reserve. 4. Rearrange other 5G3P back into RuBP requiring 3ATP. 5. Repeat as long as you have enough ???? 1Glucose requires 18ATP + 12NADPH

C. Outcomes 1. What to do with the glucose? 2. What to do with the ADP and Pi? 3. What to do with the NADP+?

IV. Photosynthetic Issues & Strategies A. Photorespiration Rubisco can also bind to O2 = Photorespiration

B. C3 Plants C3 plants go senescent rice, wheat, some grasses, and soybean. Figure 6.10

C. C4 Plants C4 plants turn CO2 into acid molecules then break up to give CO2 to Rubisco and H2O to Light Reactions. sugarcane, corn, and other grasses Figure 6.12

D. CAM Plants CAM plants completely separate light from dark reactions. cactus, pineapples, and succulents Figure 6.13

Comparing C3 with C4 leaf structures. Figure 6.11