Photosynthesis PDF

At the end of this session, you should be able to: o explain the process of photosynthesis o list the three (3) components necessary for photosynthesis to take place o explain the general reaction for photosynthesis in terms of water, light, oxygen and carbon dioxide and carbohydrate o describe th...

At the end of this session, you should be able to: o explain the process of photosynthesis o list the three (3) components necessary for photosynthesis to take place o explain the general reaction for photosynthesis in terms of water, light, oxygen and carbon dioxide and carbohydrate o describe the phenomena of transpiration, photosynthesis, and cellular respiration o describe the structure of the chloroplast o list the products of photosynthesis  TWO COMPONEN STAGES TS o Light o PHOTO – sunlight Dependent light Reactions o water (H2O) SYNTHES o carbon dioxide o Light IS - putting Independent together, (CO2) Reactions composition - process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities SO… Where do living things get energy? FOOD Food for a cell = glucose SO… How do living things get food? Different ways of obtaining food: Autotrophs – organisms that make their own food through photosynthesis (AKA: producers) Examples: plants, algae, certain bacteria Heterotrophs – organisms that consume or eat food (AKA: consumers) Examples: animals, fungi, some  TWO TYPES OF AUTOTROPHS CHEMOAUTOTROPHS PHOTOAUTOTROPHS - make food using chemical - conduct photosynthesis; use energy rather from the light energy from the sun and oxidation of inorganic water from the soil or ocean to molecules such as iron, sulfur combine CO2 into complex and magnesium organic molecules/glucose includes land and aquatic plants, algae and some bacteria  STRUCTURES OF THE PLANTS Leaf cross section Chloroplasts Mesophyll vein s CO2 O Stomata Chloroplast 2 Mesophyll cell Outer Thylakoid membran Thylakoi e Intermembran Stroma d Granum e space space Inner membrane CHEMICAL EQUATION: 6CO2 + 6H2O → C6H12O6 + 6O2 Reactants: 6 CO2 12 H2O Products: C6H12O6 6 H2O 6 O2 Photosynthesis is a Redox Reaction  LIGHT DEPENDENT REACTION LIGHT INDEPENDENT REACTION - photo part - synthesis part - convert solar energy into - uses ATP and NADPH to chemical energy reduce CO2 to glucose - occurs in the THYLAKOID MEMBRANE - occurs in the STROMA -PRODUCTS : ATP, NADPH and OXYGEN  REACTIONS OF PHOTOSYNTHESIS PHOTOSYSTEM: - light capturing unit, contains chlorophyll, the light capturing pigment ELECTRON - sequence of electron carrier TRANSPORT molecules that shuttle electrons, energy released to make ATP SYSTEM: - Electrons in chlorophyll must be replaced so that cycle may continue-these electrons come from water molecules, Oxygen is liberated from the light reactions  7 Electron transport chain 4 Electron Primary transport chain electron Fd 8 Primary acceptor e– e– NADP+ electron NADP+ + H+ acceptor Pq e– reductase NADPH 2 H+ e– 2 Cytochrome H2O complex + 1/2 O2 3 Pc 1 e– P700 e– 5 1 1 P680 Light Light 6 ATP Pigment molecules Photosystem I Photosystem II (PS I) (PS II)  e– e– e– Mill makes NADPH e– ATP e– e– n Photo e– ATP Photon Photosystem II Photosystem I  Figure 10.16 CYCLIC ELECTRON FLOW Primary acceptor Primary Fd acceptor Fd NADP+ Pq NADP+ + H+ reductase Cytochrome NADPH complex Pc Photosystem I Photosystem II ATP © 2017 Pearson Education, Inc.  Figure 10.UN03 H2O CO2 Light NADP+ ADP CALVIN LIGHT CYCLE REACTIONS ATP NADPH O2 [CH2O] (sugar) © 2017 Pearson Education, Inc. CALVIN CYCLE Calvin Cycle: Uses ATP and NADPH to convert CO2 to sugar Occurs in the stroma Uses ATP, NADPH, CO2 Produces 3-C sugar G3P (glyceraldehyde-3- phosphate) Three phases: 1. Carbon fixation 2. Reduction 3. Regeneration of RuBP (CO2 acceptor) Phase 1: 3 CO2 + RuBP (5-C sugar ribulose bisphosphate) Catalyzed by enzyme rubisco (RuBP carboxylase) Phase 2: Use 6 ATP and 6 NADPH to produce 1 net G3P Phase 3: Use 3 ATP to regenerate RuBP Alternative mechanisms of carbon fixation have evolved in hot, arid climates Photorespiration Metabolic pathway which: – Uses O2 & produces CO2 – Uses ATP – No sugar production (rubisco binds O2  breakdown of RuBP) Occurs on hot, dry bright days when stomata close (conserve H2O) Why? Early atmosphere: low O2, high CO2?  EVOLUTIONARY ADAPTATIONS 1. Problem with C3 Plants: – CO2 fixed to 3-C compound in Calvin cycle – Ex. Rice, wheat, soybeans – Hot, dry days: » partially close stomata, ↓CO2 » Photorespiration » ↓ photosynthetic output (no sugars made) 2. C4 Plants: – CO2 fixed to 4-C compound – Ex. corn, sugarcane, grass – Hot, dry days  stomata close – 2 cell types = mesophyll & bundle sheath cells » mesophyll : PEP carboxylase fixes CO2 (4- C), pump CO2 to bundle sheath » bundle sheath: CO2 used in Calvin cycle – ↓photorespiration, ↑sugar production – WHY? Advantage in hot, sunny areas 3. CAM Plants: – Crassulacean acid metabolism (CAM) – NIGHT: stomata open  CO2 enters  converts to organic acid, stored in mesophyll cells – DAY: stomata closed  light reactions supply ATP, NADPH; CO2 released from organic acids for Calvin cycle – Ex. cacti, pineapples, succulent (H 2O- storing) plants – WHY? Advantage in arid conditions End of lecture slide for the lesson Photosynthesis