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Chapter 6 Photosynthesis

Chapter 6 Photosynthesis. Section 6.1. Energy Processes for Life. Autotrophs manufacture their own food from inorganic substances Use photosynthesis to convert light energy from the sun into chemical energy. Heterotrophs cannot manufacture their own food

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Chapter 6 Photosynthesis

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  1. Chapter 6Photosynthesis Section 6.1

  2. Energy Processes for Life • Autotrophs manufacture their own food from inorganic substances • Use photosynthesis to convert light energy from the sun into chemical energy

  3. Heterotrophs cannot manufacture their own food • Must obtain food by eating autotrophs or other heterotrophs

  4. Photosynthesis • Involves a complex series of chemical reactions in which the product of one reaction is consumed in the next reaction • Biochemical pathway

  5. 6CO2 + 6H2O + solar energy  C6H12O6 + 6O2 Solar energy drives a series of chemical reactions that require carbon dioxide and water

  6. Light Absorption in Chloroplasts • Light reactions- the initial reactions in photosynthesis • Begin with the absorption of light in chloroplasts

  7. Chloroplasts • Each chloroplast is surrounded by a pair of membranes • Inside the membranes are stacks of thylakoids • The stacks are called grana • The fluid surrounding the grana is called stroma

  8. Light and Pigments • Visible spectrum- white light can be separated into an array of colors when passed through a prism • ROY G. BIV

  9. Light • Light travels in waves • The distance from the crest of one wave to the crest of another wave is called a wavelength

  10. Chloroplast Pigments • Pigments- compounds that absorb light • Chlorophyll a – absorbs more red light • Chlorophyll b – absorbs more blue light • Carotenoids – absorbs more green light

  11. Only chlorophyll a is directly involved in the light reactions of photosynthesis • Chlorophyll b assists chlorophyll a in capturing light energy (accessory pigment)

  12. In the leaves of a plant, chlorophylls are abundant • In Fall, plants lose their chlorophylls and their leaves take on the color of the carotenoids

  13. Electron Transport • Each cluster of pigment molecules is a photosystem • Two types of photosystems: photosystem I & photosystem II

  14. Light Reactions • 1. light energy excites electrons in chlorophylla molecules of photosystem II • 2. These electrons move to a primary electron acceptor • 3. The electrons are then transferred along a series of molecules called an electron transport chain

  15. 4. light excites electrons in chlorophyll a molecules of photosystem I. As these electrons move to another primary electron acceptor, they are replaced by electrons from photosystem II • 5. The electrons from photosystem I are transferred along a second electron transport chain. At the end of this chain, they combine with NADP+ and H+ to make NADPH

  16. Restoring Photosystem II • Replacement electrons come from water molecules • An enzyme inside the thylakoid splits water molecules into protons, electrons, and oxygen • 2H2O  4H+ + 4e- + O2

  17. Chemiosmosis • Synthesis of ATP • Depends on a concentration gradient of protons across a thylakoid membrane • The concentration of protons is higher inside the thylakoid

  18. ATP synthase makes ATP by adding a phosphate group to ADP • ATP synthase functions as a carrier protein

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