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PHOTOSYNTHESIS I. Autotrophs and Heterotrophs Energy for living things comes from the SUN A. Autotrophs- make their own food • Ex: plants, some bacteria, protists • Heterotrophs- obtain it from the foods they consume » Ex: animals, some bacteria, protozoans (and even fungi!) • Sooo… food as energy is either MADE through photosynthesis or OBTAINED through consumption II. Think about the Location of Photosynthesis… = WATER Other Important Parts Xylem: transports H2O Stoma: pore that allows gases to enter and exit III. CHLOROPLAST STRUCTURE A. Double-membrane structure 1outer membrane 2 inner membrane 3 granum (stack) 4 Thylakoid (individual) 5 Stroma (fluid) B. Internal Organization 1. Thylakoids: photosynthetic membranes that have clusters of chlorophyll and other pigments 2. Stroma: Fluid surrounding thylakoids IV. Light & Pigments A. Sunlight is “white” but contains mixtures of visible wavelengths B. Plants gather sun’s energy using lightabsorbing molecules called PIGMENTS MAJOR 1. Chlorophyll a - Absorbs all colors of light except green - Plays major role in light reactions of photosynthesis 2. Chlorophyll b - Yellow-green MINOR C. Plant Pigments 3. Xanthophyll - In carotenoid family - Yellow 4. Carotene - Red & orange pigments Plant pigments absorb different wavelengths of energy- which wavelength is the LEAST absorbed? Green is NOT absorbed! D. Wavelengths 1. Leaves ABSORB blue-violet & red-orange light very well 2. Green light is REFLECTED why plants look green! V. PHOTOSYNTHESIS Inputs: Light, carbon dioxide, & water Outputs: sugar and oxygen Photosynthesis Has Two Parts: VI. Light Reaction 1. Chlorophyll captures light energy in chloroplast 2. This splits H2O into oxygen and hydrogen 3. Oxygen is a "waste product" & escapes to the atmosphere 4. Energy from the reaction is used in the next stage (Calvin Cycle). B. ATP and NADPH (chemical energy) are recycled back into the system. C. Light reaction is charging up the “battery” needed to make sugars in Calvin Cycle VII. Calvin Cycle A. Does NOT use light at all B. This is the process to use energy from Light Cycle to convert CO2 into glucose Reactants: VIII.Overview of Photosynthesis Products: Two Processes Light Reaction Calvin Cycle IX. Factors Affecting Photosynthesis • Shortage of raw materials • Temperature • Light intensity