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Almost all plants are photosynthetic autotrophs, as are some bacteria and protists

THE BASICS OF PHOTOSYNTHESIS. Almost all plants are photosynthetic autotrophs, as are some bacteria and protists. Autotrophs generate their own organic matter through photosynthesis Sunlight energy is transformed to energy stored in the form of chemical bonds Why are plants green?.

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Almost all plants are photosynthetic autotrophs, as are some bacteria and protists

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  1. THE BASICS OF PHOTOSYNTHESIS • Almost all plants are photosynthetic autotrophs, as are some bacteria and protists • Autotrophs generate their own organic matter through photosynthesis • Sunlight energy is transformed to energy stored in the form of chemical bonds • Why are plants green? (c) Euglena (d) Cyanobacteria (b) Kelp (a) Mosses, ferns, and flowering plants

  2. Light Energy Harvested by Plants & Other Photosynthetic Autotrophs 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

  3. AN OVERVIEW OF PHOTOSYNTHESIS • Photosynthesis is the process by which ______________organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbondioxide Water Glucose Oxygengas PHOTOSYNTHESIS

  4. AN OVERVIEW OF PHOTOSYNTHESIS Light • The light reactions: Chloroplast NADP ADP + P Calvin cycle • The Calvin cycle makes: Light reactions

  5. Chloroplasts: Sites of Photosynthesis • Photosynthesis • Occurs in chloroplasts, organelles in certain plants • All green plant parts have chloroplasts and carry out photosynthesis • The leaves have the most chloroplasts • The green color comes from chlorophyll in the chloroplasts • The pigments absorb light energy

  6. Photosynthesis occurs in chloroplasts • In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts • A chloroplast contains: • stroma, a fluid • grana, stacks of thylakoids • The thylakoids contain chlorophyll • Chlorophyll is the green pigment that captures light for photosynthesis

  7. Chloroplast LEAF CROSS SECTION MESOPHYLL CELL • The location and structure of chloroplasts LEAF Mesophyll Intermembrane space CHLOROPLAST Outer membrane Granum Innermembrane Grana Stroma Thylakoidcompartment Stroma Thylakoid

  8. Chloroplast Pigments • Chloroplasts contain several pigments • Chlorophyll a • Chlorophyll b • Carotenoids Figure 7.7

  9. Different pigments absorb light differently

  10. Excitation of chlorophyll in a chloroplast • Loss of energy due to heat causes the photons of light to be less energetic. • Less energy translates into longer wavelength. • Energy = (Planck’s constant) x (velocity of light)/(wavelength of light) • Transition toward the red end of the visible spectrum. e e Excited state 2 Heat Light Light (fluorescence) Photon Ground state Chlorophyll molecule (a) Absorption of a photon (b) fluorescence of isolated chlorophyll in solution

  11. Cyclic Photophosphorylation • Process for ATP generation associated with some Photosynthetic Bacteria • Reaction Center => 700 nm

  12. Two types of photosystems cooperate in the light reactions Photon ATP mill Photon Water-splitting photosystem NADPH-producing photosystem

  13. Primaryelectron acceptor Electron transport Primaryelectron acceptor Electron transport chain Photons Energy forsynthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis Noncyclic Photophosphorylation • Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product

  14. How the Light Reactions Generate ATP and NADPH Primary electron acceptor NADP Energy to make Primary electron acceptor 3 2 Light Electron transport chain Light Primary electron acceptor Reaction- center chlorophyll NADPH-producing photosystem 1 Water-splitting photosystem 2 H + 1/2

  15. In the light reactions, electron transport chains generate ATP, NADPH, & O2 • Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons • The excited electrons are passed from the primary electron acceptor to electron transport chains • Their energy ends up in ___________________

  16. Chemiosmosis powers ATP synthesis in the light reactions • The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane • The flow of H+ back through the membrane is harnessed by _____________________ • In the stroma, the H+ ions combine with NADP+ to form ________________

  17. The production of ATP by chemiosmosis in photosynthesis Thylakoidcompartment(high H+) Light Light Thylakoidmembrane Antennamolecules Stroma(low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

  18. Chloroplast • A Photosynthesis Road Map Light Stroma NADP Stack of thylakoids ADP + P Light reactions Calvin cycle Sugar used for  Cellular respiration  Cellulose  Starch  Other organic compounds

  19. Review: Photosynthesis uses light energy to make food molecules • A summary of the chemical processes of photosynthesis Chloroplast Light Photosystem IIElectron transport chains Photosystem I CALVIN CYCLE Stroma Electrons Cellular respiration Cellulose Starch Other organic compounds LIGHT REACTIONS CALVIN CYCLE

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