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Unformatted text preview: • Capture of Light Energy • The Light Reactions • Carbon Fixation Lecture 12 Photosynthesis NH 4 + Plants make all complex organic molecules on their own! Stomata The overall chemical reaction of photosynthesis: 6 CO 2 + 6 H 2 O ! C 6 H 12 O 6 + 6 O 2 Is the reverse for that of respiration: C 6 H 12 O 6 + 6 O 2 ! 6 CO 2 + 6 H 2 O Photosynthesis can be divided into two pathways: ! The light reaction is driven by light energy captured by chlorophyll. It produces ATP and NADPH + H + . ! The Calvin–Benson cycle does not use light directly. It uses ATP, NADPH + H + , and CO 2 to produce sugars. An Overview of Photosynthesis Chloroplast sugars sugars CO 2 Aerobic respiration Photosynthesis C 6 H 12 O 6 + 6 O 2 + 6 H 2 O 6 CO 2 + 12 H 2 O NADP used exclusively for anabolic (biosynthetic) pathways: excess of NADPH (high [NADPH]/[NADP] ratio) to drive biosynthetic reductions. NAD used exclusively for catabolic pathways: excess of NAD (low [NADH]/[NAD] ratio) to accelerate oxidation of sugars and generation of NADH NAD and NADP have the same properties and occur in plants and animals, but are made by separate pathways and are independently regulated. Difference between NAD and NADP Is it a coincidence that photosynthesis takes place in the same narrow range of wavelength as vision?...
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