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Photosynthesis

Photosynthesis. Energy and Life. Autotroph: organisms that make their own food Heterotrophs: organisms that obtain energy from the foods they consume To live, all organisms, including plants, must release the energy in sugars and other compounds. Chemical Energy and ATP.

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Photosynthesis

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  1. Photosynthesis

  2. Energy and Life • Autotroph: organisms that make their own food • Heterotrophs: organisms that obtain energy from the foods they consume • To live, all organisms, including plants, must release the energy in sugars and other compounds

  3. Chemical Energy and ATP • ATP: (adenosine triphosphate) used by all cells as their basic energy source. • ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups. • The three phosphate groups are the key to ATP’s ability to store and release energy • ADP + P + energy  ATP

  4. Photosynthesis– plants use the energy of sunlight to convert water and carbon dioxide into high energy carbs. (glucose) and oxygen (waste)

  5. The Importance of Photosynthesis • The oxygen in the air comes from photosynthesis. The plants continue to replenish the oxygen in the air. • All of our food comes directly or indirectly from photosynthesis.

  6. The Photosynthesis Equation • The overall reaction is: 6CO2 + 6H2O LIGHT> C6H12O6 + 6O2 OR Carbon Dioxide + Water light> Glucose + Oxygen

  7. The Reactions of Photosynthesis • Remember it all occurs in the chloroplast. • Thylakoids – sac-like photosynthetic membranes inside chloroplasts, arranged in stacks called grana • Photosystems – clusters of pigments in thylakoid • Stroma – region outside of the thylakoid membrane (Calvin Cycle takes place)

  8. Light • Photosynthesis uses visible light • Only visible light with intermediate wavelengths has enough energy to cause chemical change without destroying biological molecules.

  9. Pigment • Pigments – molecules that collect light • Each pigment absorbs a particular wavelength of light in the visible spectrum • The main photosynthetic pigment is chlorophyll. • Two types chlorophyll a and chlorophyll b • Accessory pigments: • Carotenoids • Anthocyanins– not photosynthetic

  10. Pigment Absorption

  11. How it works • Light is a form of energy • When cholorphyll absorbs light, much of the energy is transferred directly to electrons in the molecule • The raising of the energy levels of these electrons makes photosynthesis work

  12. Electron Carriers • Electron carriers are used to transport high-energy electrons from chlorophyll to other molecules • NADP+ (nicotinamide adenine dinculetotide phosphate) • Accepts and hold two high energy electrons and a hydrogen ion (H+) • Makes NADPH

  13. Stage of Photosynthesis 1. 2.

  14. Light Reactions • Requires light • Produces ATP and NADPH and oxygen gas • ATP synthase is a membrane protein • Allows H+ ions to pass through the cell membrane • Transforms ADP into ATP • Think of the light reaction, as a process by which organisms "capture and store" radiant energy as they produce oxygen gas.

  15. The Dark Reactions • The dark reactions take place outside the thylakoid membrane. • Uses ATP and NADPH and CO2 from the light reaction to produce high energy sugars (glucose) • Carbon dioxide is broken and “fixed” into glucose or fructose molecules in the CALVIN CYCLE!

  16. Factors Affecting Photosynthesis • The amount of water • Temperature. • Best between 0 and 35 ºC. • Intensity of light

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