Photosynthesis By: Muhammad Iqbal Khan SS Biology Email ID mikhan1313@yahoo.com Contact: 0923135448175

Lecture 3 Outline (Ch. 8) Photosynthesis overview A. Purpose B. Location The light vs. the “dark” reaction Chloroplasts pigments A. Light absorption B. Types Light reactions A. Photosystems B. Photophosphorylation V. The light independent reaction (“dark” reaction) A. Carbon “fixation” B. Reduction C. Regeneration VI. Alternative plants

Photosynthesis - overview

Photosynthesis - overview Overall purpose: • photosynthesis – light chemical energy • complements respiration Energy for all life on earth ultimately comes from photosynthesis

Cellular Respiration vs. Photosynthesis (Exergonic) Photosynthesis: (Endergonic)

Photosynthesis – chloroplast recap Outer membrane Inner membrane Thylakoid membrane Stroma Thylakoid space Intermembrane space

Photosynthesis - overview 1. light rxn: store energy & split water – “photo” NADPH & ATP 2. dark rxn: “fix” CO2 & make sugars – “synthesis” Calvin cycle

Redox Reactions 6CO2 + 12H2O + light energy C6H12O6 + 6O2 + 6H2O Equation for photosynthesis

Photosynthesis - overview • light reactions: • dark reactions: – thylakoid membrane – stroma Light H2O Chloroplast Reactions NADP+ P ADP + ATP NADPH O2 Calvin Cycle CO2 [CH2O] (sugar) – thylakoid space

Photosynthesis – light absorption • visible light ~380 to 750 nm • chloroplast pigments – abs blue-violet & red - transmit and reflect green

Photosynthesis – light absorption • pigments: • chlorophyll a -energy-absorbing ring -hydrocarbon tail • accessory pigments - chlorophyll b - carotenoids - photoprotective

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