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Photosynthesis

Photosynthesis. Defined as the process of transferring light energy into chemical energy. Chloroplasts – part of the plant cell were photosynthesis occurs. Pg. 112 (green dots) Thylakoid – a membrane disc that hold chlorophyll in the chloroplast. Granum – a stack of thylakoids.

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Photosynthesis

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  1. Photosynthesis • Defined as the process of transferring light energy into chemical energy. • Chloroplasts – part of the plant cell were photosynthesis occurs. Pg. 112 (green dots) • Thylakoid – a membrane disc that hold chlorophyll in the chloroplast. • Granum – a stack of thylakoids. • Stroma – fluid that surrounds the thylakoids in the chloroplast.

  2. The 3 reactions of photosynthesis • 1. Light absorption by chlorophyll • 2. Light Reaction • 3. Calvin Cycle (dark reaction) • So, what happens when light strikes a chlorophyll molecule? • 1. Light is given off • 2. Heat is given off • 3. It is used to create energy

  3. The light causes the chlorophyll molecules to vibrate and release electrons, which is electrical energy. Then in the second phase the electrical energy is converted to chemical energy. • The transport of these electrons occurs in the photosystems of the light reaction.

  4. Photosystem II is where electrons are used as electrical energy. • Photosystem I is where electrons are used as chemical energy. • The energy produced from both photosystems is stored as ATP & NADPH  Stored Energy. • Pg. 114 & 115  Steps

  5. Calvin Cycle • The stored energy in the light reaction (ATP & NADPH) is used in the Calvin cycle. Also called Dark Reaction or Light-independent Reaction. • CO2 is used to start the cycle. Hydrogen is then added with the help of ATP & NADPH to complete the cycle, in which sugars are produced and oxygen is released. • It stores sugars & starches in the leaves. • Plants stay alive for weeks without light because of the stored sugars & starches.

  6. Water + Carbon Dioxide  Glucose + Oxygen as a by-product • Glucose (C6H12O6) is produced in the Calvin cycle (Dark Reaction). • Pg. 117  Steps • Plants are autotrophs & not mobile • Animals are heterotrophs & mobile • All of the reactions take place in the chloroplast of a plant cell (contains chlorophyll) • Calvin Cycle  stroma • Light reactions  thylakoid membrane

  7. C4 vs. C3 Plants • C4 plants are adapted to environments with high temperatures and dry conditions. Produce more sugars. • Produce a 4-carbon compound of PGA • They have enzymes that enable this. • Ex. Corn, crabgrass, buffalo grass, sugar cane • Warm Season Plants • C3 plants are adapted to cooler climates. • Produce a 3-carbon compound of PGA • Ex. Wheat, blue-grass, fescue • Cool Season Plants

  8. CAM plants undergo a process where their stomata are open at night & closed during the day. Why would they do this? Examples? • This occurs in very hot & dry climates. • Cactuses & Pineapples • Where does the energy come from in plants? • What are the colors of visible light? • ROYGBIV • What color is most absorbed by plants?

  9. Plants use all the colors of the spectrum except green. It reflects green the most. • Two types of chlorophyll  A & B. • Chlorophyll A does photosynthesis, while chlorophyll B helps. Chlorophyll A prefers the red wavelength of visible light, which means most plants should grow better with that wavelength. Pg. 113 • During the fall plants start to lose their chlorophyll and other accessory pigments are now displayed. • Carotenoids, xanthophylls, anthocyanins • Video - photosynthesis

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