Energy & Life 1

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Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food. 3

 Autotrophs include organisms that make their own food  Autotrophs can use the sun’s energy directly 4 Euglena

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 Involves the Use Of light Energy to convert Water (H 2 0) and Carbon Dioxide (CO 2 ) into Oxygen (O 2 ) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches 6

Many Scientists Have Contributed To Understanding Photosynthesis Many Scientists Have Contributed To Understanding Photosynthesis Early Research Focused On The Overall Process Early Research Focused On The Overall Process Later Researchers Investigated The Detailed Chemical Pathways Later Researchers Investigated The Detailed Chemical Pathways 7

 First to trace the path that carbon (CO 2 ) takes in forming Glucose  Does NOT require sunlight  Called the Calvin Cycle or Light Independent Reaction  Also known as the Dark Reaction 8

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In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments Chlorophyll is the primary light-absorbing pigment in autotrophs Chlorophyll is found inside chloroplasts 10

 Energy From The Sun Enters Earth’s Biosphere As Photons  Photon = Light Energy Unit  Light Contains A Mixture Of Wavelengths  Different Wavelengths Have Different Colors 11

 Different pigments absorb different wavelengths of light  Photons of light “excite” electrons in the plant’s pigments  Excited electrons carry the absorbed energy  Excited electrons move to HIGHER energy levels 12

There are 2 main types of chlorophyll molecules: Chlorophyll a found in all plants, algae, & cyanobacteria Chlorophyll b is an accessory pigment. Transfer the light it absorbed to chlorophyll a A third type, chlorophyll c, is found in dinoflagellates, brown algae and diatoms. Green light is reflected from the chlorophyll giving the plants its green color. 13

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 Double membrane organelle  Outer membrane smooth  Inner membrane forms stacks of connected sacs called thylakoids  Thylakoid stack is called the granun (grana-plural)  Gel-like material around grana called stroma 16

 Light Independent reactions occur here  ATP used to make carbohydrates like glucose  Location of the Calvin Cycle 17

 Light Dependent reactions occur here  Photosystems are made up of clusters of chlorophyll molecules  Photosystems are embedded in the thylakoid membranes 18

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 Nicotinamide Adenine Dinucleotide Phosphate (NADP + )  NADP + = Reduced Form  Picks Up 2 high-energy electrons and H + from the Light Reaction to form NADPH  NADPH carries energy to be passed on to another molecule 20

 Occurs across the thylakoid membranes  Uses light energy  Produce Oxygen from water  Convert ADP to ATP  Also convert NADP + into the energy carrier NADPH 21

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Photosystem absorbs light energy Electrons are energized and passed to the Electron Transport Chain Lost electrons are replaced from the splitting of water into 2H +, free electrons, and Oxygen 2H + pumped across thylakoid membrane 23

High-energy electrons are moved to Photosystem I through the Electron Transport Chain Energy is used to transport H + from stroma to inner thylakoid membrane NADP+ converted to NADPH when it picks up 2 electrons & H+ 24

Enzyme in thylakoid membrane called ATP Synthase As H+ ions passed through thylakoid membrane, enzyme binds them to ADP Forms ATP for cellular 25

Reactants: H2OH2OH2OH2O  Light Energy Energy Products:  ATP  NADPH 26

 ATP & NADPH from light reactions used as energy  Atmospheric C0 2 is used to make sugars like glucose and fructose  Six-carbon Sugars made during the Calvin Cycle  Occurs in the stroma 27

28 It takes two turns in the calvin cycle to create to create 1 carbohydrate. The carbohydrate is a glucose sugar molecule.

29 Light Independent Reaction Summary Reactants:  Energy molecules used are ATP and Nadph  CO 2Carbon Fixation Products:  Glucose

 Amount of available water  Temperature  Amount of available light energy  Color of Light 30