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5.1 Energy & Photosynthesis Chapter 9 Energy: All organisms require energy for survival All energy in food ultimately comes from the sun Energy: How do we get it? Make it! Autotrophs Organisms that make their own food (glucose) using energy from the sun Examples: plants, algae & some bacteria Energy: How do we get it? Eat it! Heterotrophs Organisms that eat plants or animals to get energy Examples: animals & fungi Energy: What’s it all for? Why To move, breathe & reproduce Why do organisms need energy? do cells need energy? Active transport, cell division & make biomolecules Where does energy come from? Food: Carbs – quick energy; Lipids – long term energy Energy Molecules: ATP ADP Energy Molecules: ATP ATP (adenosine triphosphate) 1 ribose (sugar) molecule 3 phosphate groups Adenine (nitrogenous base) Energy Molecules: ADP ADP (adenosine diphosphate) 1 ribose (sugar) molecule 2 phosphate groups Adenine (nitrogenous base) Created when ATP loses energy & a phosphate Energy Molecules So what happens? ATP ADP Bond between 2nd & 3rd phosphate is broken Energy is released Energy can be used by the cell So what happens? ADP ATP Energy is stored when 3rd phosphate adds to ADP How do cells get ATP? Break down carbohydrates & lipids Creates energy – energy used to make ATP Where do animals get carbohydrates & lipids from? Their FOOD That food is produced by autotrophs in the process of photosynthesis Photosynthesis Ability to capture light energy from the sun and change it into chemical bond energy while making oxygen Photosynthesis Equation 6CO2 + 6H2O + Light energy C6H12O6 + 6O2 Photosynthesis Questions: Where does it occur in plants? What are the reactants? How do the reactants get into the plant? What are the products? What happens to the products? Location? In the chloroplast of plant cells Where does it occur? Chloroplast structure: Thylakoids: Sacs of membrane with pigment molecules Grana: Stacks of thylakoids Stroma: Liquid surrounding thylakoids Contains enzymes for PS Photosynthesis Pigments Photosynthesis Pigments Pigments in the plant chloroplast & vacuole absorb light energy Chlorophyll is the main pigment found in plant cell chloroplasts Reflect green light Photosynthesis process Occur in two steps: Light-dependent reactions Purpose: Make energy for light-independent reactions Light-independent reactions Also called Calvin cycle Purpose: Use energy from light reactions to make glucose Lightdependent Reactions Lightindependent Reactions thylakoid Glucose Photosynthesis process: light-dependent reactions Location: Thylakoids 1. Light energy is absorbed by chlorophyll 1. 2. 3. Chlorophyll electrons gain lots of energy NADPH carries high-energy electrons to the Calvin Cycle Light Energy used to make ATP for Calvin Cycle NADP+ NADPH NADP+ Photosynthesis process: light-dependent reactions Water is split to produce oxygen and hydrogen atoms 4. 2H2O + Light 2H2 + O2 Oxygen is released as a product; released through the stomata of leaves. Photosynthesis process: light-dependent reactions Used: Light Made: energy ATP NADPH H 2O Oxygen Light-independent rxns (product) Photosynthesis process: light-independent reactions Called No Calvin cycle light required! Location: Stroma of chloroplast Photosynthesis process: light-independent reactions ATP broken apart to release energy 1. ATP ADP + P + energy Energy used to bond electrons from NADPH with CO2 to make glucose 2. 1. Equation: CO2 + electrons C6H12O6 ADP goes back to light reactions to get recharged 3. Turned back into ATP Photosynthesis process: light-independent reactions Used: Made: CO2 ATP (from light rxns) NADPH (from light rxns) GLUCOSE !!! Photosynthesis review: Where How did the CO2 come from? did water enter the plant? What What absorbed the sunlight? reactant is used in the lightindependent reactions? Photosynthesis questions: What is made in the light-dependent reactions that is used in the lightindependent reactions? What reactant is responsible for making oxygen? Photosynthesis questions Where do the light-dependent reactions take place? Where do the light-independent reactions take place? What is the final product of the lightindependent reactions? H2O O2 Light ATP CO2 Glucose H NADPH ADP Factors that influence PS Rates Lack of water Example/Adaptation: Desert plants/conifers (pines): waxy coating and “needle” leaves to reduce water loss Factors that influence PS Rates Temperature: influences enzymes involved in the PS reactions What is the best temperature? Factors that Influence PS rates Intensity of light (varies by plant) Excess UV rays/sunlight can decrease PS
