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Photosynthesis

Photosynthesis. Anthocyanin (fall) and phycobilins (red algae and cyanobacteria ) are accessory pigments They absorb other wavelengths of color Review : Light travels in waves and is in packets called photons. Photosynthesizers use wavelengths between 380 to 750 nm. Photosynthesis.

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Photosynthesis

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  1. Photosynthesis • Anthocyanin (fall) and phycobilins (red algae and cyanobacteria) are accessory pigments • They absorb other wavelengths of color • Review: Light travels in waves and is in packets called photons. Photosynthesizers use wavelengths between 380 to 750 nm.

  2. Photosynthesis • Pigments catch the suns energy- by exciting electrons and moving them to higher energy levels. When they fall back to the lower energy level they emit energy that the plant can use to make food or conduct sugar producing reactions.

  3. Photosynthesis

  4. Photosynthesis: Light Dependent Reaction

  5. Photosynthesis: Light Dependent Reaction • Light Dependent Reactions • Photosystems, located in the thylakoid membrane , contain pigments (ie. chlorophyll). When a pigment catches a photon of the right energy level, its electrons get excited. (Jump to a higher energy level)

  6. Photosynthesis: Light Dependent Reaction • The excitation energy is transferred to the reaction center, the energetic electron is transferred to an electron receptor.

  7. Photosynthesis: Light Dependent Reaction • Electron transport – allows the excited electrons to move from carrier to carrier. During the electron’s trip protons (H+) transport across the membrane creating a proton gradient. NADP acts as the electron and proton acceptor and reduces to become NADPH.

  8. Photosynthesis: Light Dependent Reaction

  9. Photosynthesis: Light Dependent Reaction

  10. Photosynthesis: Light Dependent Reaction • The protons that accumulate in the thylakoid compartment now flow back across the membrane through ATP synthaseto produce ATP.

  11. Photosynthesis: Light Dependent Reaction

  12. Photosynthesis: Light Independent Reaction • Light independent Reaction • Takes place in the stroma of the chloroplast • Requires the input of ATP and NADPH made in the light dependent reactions • Results in a 3 carbon fragment PGAL (G3P) which can be made into glucose, proteins or lipids

  13. Photosynthesis: Light Independent Reaction Complete student hand out of Calvin- Benson Cycle

  14. Different plants, Different pathways • Plants control the movement of water and gases through tiny openings called stomata.

  15. Different plants, Different pathways • C3 plants such as beans and sunflowers must be well irrigated in hot dry climates. • To preserve H2O, the stomata stay closed during the day which traps oxygen in the plant and does not allow carbon dioxide to enter. If there is too much oxygen, the enzymes insert it into the Calvin- Benson cycle.

  16. Different plants, Different pathways • C4 plants such as grasses and corn conduct the carbon fixation (C4) cycle in a separate cell then the Calvin- Benson cycle. • If the reactions are separated the enzymes can not be confused by the presence of too much oxygen.

  17. Different plants, Different pathways • CAM plants such as cacti have thick surface layers and water storing tissues. • CAM plants open their stomata at night to fix carbon and run a C4 cycle. The Calvin- Benson cycle is then run during the day. Why only open stomata during the night ?

  18. Questions?

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