Photosynthesis

1. Photosynthesis

2. Autotrophs • Auto = self • Troph = eating • Organisms that can produce their own food (energy) from inorganic materials (sunlight)

3. Heterotroph • Hetero = other • Troph = eating • Organisms that cannot make its own food. Requires organic compounds (other organisms) for its principle source of food.

4. Chemical Energy and ATP • All cells use chemical energy carried by ATP-Adenosine triphosphate. • Cells use ATP for functions such as building molecules and moving material through active transport.

5. ATP • The energy carried by ATP is released when a phosphate group is removed from the molecule. • ATP become ADP (Adenosine diphosphate) • ADP can become ATP again through a series of chemical reactions.

6. ATP • ATP is produced during the breakdown of carbon-based molecules. • Different foods provide different amounts of ATP. • Carbohydrates (glucose) can make ~ 36 molecules of ATP • Lipids can make ~ 146 molecules

7. Special Creatures • Some organisms do not need sunlight and photosynthesis as a source of energy. • Some organisms live near cracks in the ocean and never see sunlight • Chemosynthesis • Process by which some organisms use chemical energy instead of light energy to make energy-storing carbon-based molecules

8. Photosynthetic Organisms are Producers. • Producers • Produce the chemical energy for themselves and for other organisms. • Photosynthesis • A process that captures energy from sunlight to make sugars that store chemical energy. • Chlorophyll • A molecule in chloroplasts that absorb some of the energy in visible light

9. Properties of Light • Organisms use only a small range of wavelengths for photosynthesis, vision, and other processes. • Most of these wavelengths are the ones we see as visible light, a small part of the electromagnetic spectrum from the sun. • Light energy is packages as photons, which vary in energy as a function of wavelength. • The shortest are gamma rays with the highest energy; longer are radio waves with the lowest energy. • Photoautotrophs use only a small range (380-750 nm) of wavelengths for photosynthesis.

10. From Sunlight to Photosynthesis • Pigment molecules on the thylakoid membranes absorb photons. • The chlorophylls in green leaves mask the accessory pigments until autumn when the chlorophyll content declines. • A pigment absorbs light of specific wavelengths by acting as an antenna for receiving photon energy. • Chlorophyll a and b pigments absorb blue and red, but reflect green (leaves). • Carotenoid pigments absorb blue-violet and blue-green but reflect yellow, orange, and red. • Xanthophylls reflect yellow, brown, purple, or blue light; anthocyanins reflect red and purple light in fruit and flowers; phycobilines reflect red or blue-green light and are accessory pigments found in red algae and cyanobacteria.

11. Harvesting the Rainbow • Violet and red light are the wavelengths best suited for photosynthesis.

12. Photosynthesis in Chloroplasts • Both stages of photosynthesis occur in the chloroplast. • The semifluid interior (stroma) is the site for the second series of photosynthesis reactions. • Flattened sacs, thylakoids, interconnected by channels weave through the stroma; the first reactions occur here. • In the thylakoid membranes, pigments are organized into clusters called photosystems, each consisting of 200-300 pigment molecules capable of trapping energy from the sun.

13. Photosynthesis in Chloroplasts • Light-dependent reactions • Convert light energy to the chemical bond energy of ATP. • Water is split to release oxygen. • NADP+ picks up electrons to become NADPH to be used later. • Light-independent reactions • Assemble sugars and other organic molecules using ATP, NADPH, and CO2.

14. First Stage: Light-Dependent Reaction • Capture and transfer energy. • There are two photosystems involved: photosystem II and photosystem I

15. Light-Dependent Reaction • Chlorophyll and other light-absorbing molecules capture energy from sunlight. • Water molecules are broken down into hydrogen ions, electrons, and oxygen gas (waste) • Sugars are NOT MADE during this part of photosynthesis Day 1

16. Light Dependent Reaction: Photosystem II • Chlorophyll and other light absorbing molecules absorb energy from sunlight and that energy is transferred into chloropyll. • The energy is then transferred to electrons. • 1. Energy is absorbed in sunlight • High energy electrons leave the chorophyll and enter the electron transport chain (a series of proteins in the thylakoid) • 2. Water molecules split • 3. Hydrogen ions transported

17. Light Dependent Reaction: Photosystem I • Chlorophyll and other light-absorbing molecules absorb sunlight and add it to the electrons from photosystem II • 4. Energy is absorbed from sunlight. Electrons are energized. • 5. NADPH produced. • In photosynthesis NADPH functions like ATP. • The molecules of NADPH go to light-independent reactions.

18. ATP Production • Final part of the light-reaction. • 6. Hydrogen ion diffusion • H+ ions flow through the thylakoid. • 7. ATP produced • ATP synthase take the ions as they flow and makes ATP by adding phosphate groups to ADP.

19. Light Dependent Reaction: Photosystem II and Photosystem I

20. Summary of Light-Dependent Reactions • PRODUCTS ARE: • NADPH • Used later to make sugar. • ATP • Used later to make sugar. • Oxygen • Given off as a waste.

21. 2nd Stage: Light Independent Reaction • Uses energy from the first stage to make sugar. • Light-independent reactions take place ANY time that energy is available (it doesn’t need sunlight). • Light-independent reactions use the NADPH and ATP made during the light-dependent reactions to make sugar.

22. The Calvin-Benson Cycle • Uses the NADPH and ATP from the light-dependent reaction, and CO2 from the atmosphere to make simple sugars.

23. The Calvin-Benson Cycle • 1. Carbon dioxide added. • CO2 molecules are added to five-carbon molecules already in the Calvin Cycle (RuBP). • six-carbon molecules are formed . • 2. Three-carbon molecules formed (PGA). • ATP and NADPH is used to split the six-carbon molecules into two three-carbon molecules.

24. The Calvin-Benson Cycle • 3. Three-carbon molecules exit. • Most of the three-carbon molecules will stay IN the Calvin Cycle. • ONE high energy three-carbon molecule will leave the cycle. • When TWO three-carbon molecules leave the cycle, they will bond together to build a six-carbon sugar molecule. • Glucose (C6H12O6)

25. The Calvin-Benson Cycle • 4. Three-carbon molecules recycled (PGAL). • Energy from ATP is used to change the three-carbon molecules that stayed in the cycle to five-carbon molecules. • These five-carbon molecules stay in the Calvin Cycle. • They are added to new CO2 molecules that enter the cycle.

26. The Calvin-Benson Cycle

27. Summary of Light-Independent Reactions • PRODUCTS ARE: • Glucose • Used to store energy. • NADP+ • Return to the light-dependent reaction. • Will be changed into NADPH there. • ADP • Return to the light-dependent reaction. • Will be changed into ATP there.

28. Functions of Photosynthesis • Provides material for plant growth and development. • Simple sugars are bonded together to form complex sugars like cellulose and starch. • Starches store energy for the plant. • Cellulose is a major component of the cell wall. • Helps regulate the Earth’s environment. • Removes CO2 from the atmosphere.

29. Photosynthetic Equation • 6CO2 + 6H2O C6H12O6 + 6O2 • Light Dependent Reactions • Includes Photosystem II • Electron Transport Chain • Photosystem I • Light Independent Reactions • Includes the Calvin Cycle

30. Photosynthetic Equation