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Pigments and Leaf Structure

Pigments and Leaf Structure . Photosynthesis. Photosynthesis - the process by which light energy is captured and converted into chemical energy that is stored in organic compounds (glucose!) Autotrophs: organisms that make their own food. (plants, algae, and some bacteria)

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Pigments and Leaf Structure

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  1. Pigments and Leaf Structure

  2. Photosynthesis • Photosynthesis- the process by which light energy is captured and converted into chemical energy that is stored in organic compounds (glucose!) • Autotrophs: organisms that make their own food. (plants, algae, and some bacteria) • Photoautotrophs: use light to make own food • Chemoautotrophs: use chemicals to make own food (they do chemosynthesis) • Heterotrophs: organisms that obtain food by eating plants or other animals (animals, protists, and some bacteria)

  3. Chemosynthesis • Chemosynthesis: the process in which carbohydrates are made from carbon dioxide and water using chemical nutrients as the energy source, rather than the sunlight used for energy in photosynthesis. • Some bacteria convert energy by Chemosynthesis: • Carbon dioxide + water + hydrogen sulfide  glucose + sulfuric acid 6CO2+ 6H2O + 3 H2S  C6H12O6 + 3H2SO4 • Plants convert energy by Photosynthesis: • Carbon dioxide + water + sunlight (absorbed by chlorophyll)  glucose + oxygen • 6CO2 + 6H2O + sunlight (absorbed by chlorophyll)  C6H12O6 + O2

  4. Electromagnetic Spectrum

  5. Pigments and Absorption • Light-absorbing pigments are used in photosynthesis. • Main pigments: • chlorophyll a • chlorophyll b ** these reflect green light.** • Some other plant pigments are carotenoids (reflect yellow, orange, brown), anthocyanins (reflect red and purple), and xanthophylls (reflect yellow).

  6. Pigments and Absorption • Chlorophyll a absorbs light mostly in the blue-violet and red regions of the visible spectrum • Chlorophyll b absorbs light mostly in the blue and red regions of the visible spectrum • Carotenoidsabsorb light mostly in the violet and blue regions of the visible spectrum • Xanthophylls absorb light mostly in the blue and purple regions of the visible spectrum • Anthocyanins absorb light mostly in the blue, green, blue, and blue-green regions of the visible spectrum

  7. BASIC FORMULA FOR PHOTOSYNTHESIS • 6CO2 + 6H2O + light energy  C6H12O6(glucose) + 6O2 • Photosynthesis uses a biochemical pathway, or a complex series of chemical reactions in which the product of one reaction is consumed in the next reaction

  8. Leaf Structure Waxy cuticle Epidermis Palisade mesophyll – lots of chloroplasts Spongy mesophyll Vein with xylem and phloem Guard cells stoma

  9. leaf: a plant organ where food is made by photosynthesis • vein: contains vascular tissue which transports materials to and from the leaf • xylem: transports water and nutrients from the roots to the stem and then to the leaf • phloem: transports food that is made in the leaf to the stem and roots • stoma (plural- stomata): small openings in the lower surface of the leaf that allow gases to move into and out of the leaf (CO2, O2, and water vapor) • guard cells: “gates” that open and close the stomata • Leaf layers: • epidermis: the outer layer of the leaf that is covered with a waxy cuticle to prevent water loss • palisade mesophyll: the layer of narrow, tightly packed cells which contain many chloroplasts; a primary site of photosynthesis in the leaf • spongy mesophyll: loosely packed cells which contain air spaces that allow diffusion of carbon dioxide; also a site of photosynthesis (contains chloroplasts)

  10. Structures of Photosynthesis

  11. Details of Photosynthesis • Photosynthesis reactions take place inside the membrane of the chloroplasts, within the thylakoids, flattened sacs that are layered together to form stacks called granum (plural is grana). The solution surrounding the thylakoids is called the stroma. • 2 parts of Photosynthesis: • Light-dependent reactions (or just light reactions) • Light-independent reactions (the Calvin cycle)

  12. Light-Dependent Reaction • Light-dependent reactions (or just light reactions) • occur inside the thylakoids of the chloroplast • light is absorbed by chlorophyll; water is split into H+, electrons, and O2 • 2 very energy-rich molecules are also made: ATP and NADPH

  13. Light-Independent Reaction/Calvin Cycle/Dark Reaction • Light-independent reactions (the Calvin cycle) • occur in the stroma of the chloroplast • CO2 is used in this part; the ATP and NADPH from the light reactions are also used • Simple sugars are made during the Calvin cycle: [CH2O] or glucose, C6H12O6

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