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PhotosynthesiS

Kelp. Cyanobacteria. PhotosynthesiS. Green-leaved flowering plants. General Equation. visible light 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 chlorophyll. Purpose. To synthesize carbohydrates (i.e glucose) using the Sun’s energy. Location. chloroplast. Chloroplasts.

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PhotosynthesiS

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  1. Kelp Cyanobacteria PhotosynthesiS Green-leaved flowering plants

  2. General Equation visible light 6CO2 + 6H2O C6H12O6+ 6O2 chlorophyll

  3. Purpose • To synthesize carbohydrates (i.e glucose) using the Sun’s energy Location • chloroplast

  4. Chloroplasts • 2 layered membrane (inner & outer membrane) • Stroma – pr- rich semi-liquid • Thylakoids – membrane bound sacs • Membranes contain chlorophyll & ETC's • Stacked thylakoids  Grana

  5. Chloroplasts • Lamellae – unstacked thylakoid • Connect adjacent grana In each plant cell, there are between 40 and 200 chloroplasts…in a typical leaf, there are 500 000 chloroplasts per square mm!

  6. Light • A form of E that travels in wave packets called photons • Photons carry specific amounts of energy

  7. Light • Each wavelength (colour) of visible light is associated with photons of one distinct amount of energy

  8. Light Photons w/ short wavelengths have high E, long wavelengths have low E The wavelength of a photon (and thus the colour of light) that an atom or molecule absorbs is determined by energy levels of the electrons in that atom or molecule

  9. Pg 158

  10. Chlorophyll & Accessory Pigments

  11. Pigment Molecules • Compounds that absorb visible light • Plants have many different types of pigment molecules, each absorb light in a different region of the spectrum.

  12. Absorbance Spectrum • A graph that shows the relative amounts of light of different wavelengths that a compound absorbs Pg 158

  13. Pigment Molecules • Pigment molecules appear the colour of the light wavelength they reflect. Pg 158

  14. Chlorophyll • Green coloured pigment found in chloroplasts • Absorbs light E and begins the process of PS

  15. Chlorophyll Structure • Porphyrin ring (w/ Mg at centre) • e- in ring absorb the light E to begin PS • Long hydrocarbon tail • Anchors chlorophyll molecule in membrane

  16. 2 Types of Chlorophyll Chlorophyll a • Methyl group (CH3) attached to ring • Primary light-absorbing pigment in photosynthetic organisms

  17. 2 Types of Chlorophyll Chlorophyll b • Aldehyde group (-COH) attached to ring • Acts as an accessory pigment • Absorbs photons that chlorophyll a absorbs poorly or not at all

  18. Carotenoids • Orange and yellow accessory pigments • Absorb light which would otherwise damage chlorophyll • Then lose the E as heat

  19. Carotenoids • Example: -carotene = orange colour of carrots and autumn leaves.

  20. Action Spectrum • A graph that shows the relative effectiveness of different wavelengths of light for promoting photosynthesis Pg 159

  21. Light E is not absorbed by individual pigment molecules...light E is absorbed by a network of chlorophyll molecules known as a photosystem.

  22. Photosystems • Located in the thylakoid membranes • Made up of chlorophyll molecules, accessory pigments and proteins

  23. Photosystemspg 159 Contain Antenna Complex Chlorophyll molecules that collect and channel E This E causes e- in chlorophyll to become energized E is passed through photosystem to the rxn center

  24. Photosystems Contain Reaction Centre Protein containing Chlorophyll a that absorbs light E and releases an excited e- to the primary e- acceptor to begin the light rxn

  25. Photosystems Pg 159

  26. Two Photosystems in PS • PSI (P700) – chlorophyll a absorbs wavelengths of 700 nm • PSII (P680) – chlorophyll a absorbs wavelengths of 680 nm

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