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Photosynthesis

Photosynthesis. How cells acquire energy. Review. What is a heterotroph? What is an autotroph? What is the main source of energy? What is energy?. Potential Energy. Stored energy Based on position of an object. Kinetic Energy. Energy that moving objects/particles possess.

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Photosynthesis

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  1. Photosynthesis How cells acquire energy

  2. Review • What is a heterotroph? • What is an autotroph? • What is the main source of energy? • What is energy?

  3. Potential Energy • Stored energy • Based on position of an object

  4. Kinetic Energy • Energy that moving objects/particles possess

  5. Radiant Energy • Energy in the form of light

  6. Sunlight Energy • Continual input of solar energy into Earth’s atmosphere • Almost 1/3 is reflected back into space • Of the energy that reaches Earth’s surface, about 1% is intercepted by photoautotrophs (organisms that capture light energy to make food) • This means that only 10% of the energy is passed to each trophic level

  7. Electromagnetic Spectrum Shortest Gamma rays wavelength X-rays UV radiation Visible light Infrared radiation Microwaves Longest Radio waves wavelength

  8. How does the energy travel to the Earth? • Light • Sunlight is perceived as “white” light • Actually is a mixture of wavelengths • Light absorbing pigments (CHLOROPHYLL) gather the sun’s energy

  9. Figure 8-5: Chlorophyll Light Absorption Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll absorbs light very well in the blue and red regions of the visible spectrum. It does not absorb green which is why the plant is green. • Light Absorption • http://mc2.cchem.berkeley.edu/Java/

  10. Chloroplasts Organelles of photosynthesis

  11. Pigment Structure • Light-catching part of molecule often has alternating single and double bonds • These bonds contain electrons that are capable of being moved to higher energy levels by absorbing light

  12. Chlorophylls Main pigments in most photoautotrophs chlorophyll a Wavelength absorption (%) chlorophyll b Wavelength (nanometers)

  13. Variety of Pigments Chlorophylls a and b-reflect green Carotenoids-reflect red, yellow, orange • Carotenes - pure hydrocarbons • Xanthophylls - contain oxygen Anthocyanins-reflects red to purple (flowers) Phycobilins-reflects red to purple (flowers)

  14. Pigments in Photosynthesis • Bacteria • Pigments in plasma membranes • Plants • Pigments embedded in thylakoid membrane system • Pigments and proteins organized into photosystems • Photosystems located next to electron transport systems

  15. Chloroplast Structure

  16. Thylakoid Membrane • Contain pigments that absorb light • Chlorophyll is the main one • Light dependent reaction occurs here

  17. Stroma • Location of the Calvin cycle • 13 reactions in three phases • 13 enzymes catalize the steps

  18. Photosynthesis: An overview

  19. Photosynthesis Equation: light 6CO2+6H2O C6H12O6+6O2

  20. Chemical Energy & ATP • Energy also comes in chemical compounds. • Adenosine Triphosphate – ATP • Consists of a nitrogen-containing compound (adenine), a 5-C sugar (ribose), & THREE phosphate groups • Adenosine Diphosphate – ADP • Consists of a nitrogen-containing compound (adenine), a 5-C sugar (ribose), & TWO phosphate groups

  21. ATP & ADP

  22. ATP Adenine Ribose Phosphate

  23. Why is ATP important? • Stores Energy for all types of cells. • Organelles can move throughout cell. • Active Transport • Sodium-Potassium pump

  24. Downfalls??? • ATP only stores small quantities of energy. • Only allows a few seconds of activity. • Glucose stores 90 times as much energy. • Possible Solution??? • Store glucose and use it to make ATP.

  25. NADPH • Another energy carrying molecule • NADP+ + H+ + 2e- NADPH • Energy carrierenergystored energy • NADPH NADP+ + H+ + 2e- • Stored energyEnergy carrierreleased energy

  26. Water CO2 Sugars O2 Photosynthesis: An Overview LIGHT Chloroplast NADP+ ADP + P Light- Dependent Reactions Calvin Cycle ATP NADPH

  27. Light-Dependent Reactions • Require light • Produce oxygen gas • Convert ADP and NADP+ into energy carriers ATP and NADPH

  28. Of course it’s not that easy… It is strongly recommended that you look at your book diagrams before the test and read your notes at the same time!

  29. There are 2 Photosystems • When a pigment molecule absorbs a photon, one of the pigment’s electrons jumps to an energy level farther from the nucleus, making it have an ‘excited’ state • Both photosystems capture solar power

  30. Photosystem II Extra Info… • Chlorophyll a is called P680 Photosystem I • Chlorophyll a is called P700 You don’t need to know this, but it has to do with the wavelengths of the colors they absorb. 680 nm is the red wavelength and 700 nm is the far red wavelength

  31. Differences • Photosystem II • Water molecules are split, allows ADP to become ATP again

  32. Electron Transport Chain • Light energy is converted to chemical energy of ATP and NADPH • Electrons removed from water pass from photosystem II to photosystem I to NADP+, providing energy for the synthesis of ATP

  33. ATP and NADPH move to the Calvin Cycle

  34. Calvin Cycle (Melvin Calvin) • Plants use energy that ATP and NADPH contain to build high-energy compounds that can be stored for a long time • Produces high-energy sugars • Light-independent reaction • Sugar factory within the chloroplast

  35. Calvin Cycle— • Carbon fixation—enzyme called rubisco combines with Carbon Dioxide, and splits • Reduction—two chemical reactions consume energy from ATP and oxidize NADPH. Produces energy rich three carbon sugars • G3P released—Net product of photosynthesis—used to make glucose • Regeneration of RuBP—ATP rearranges G3P to form more RuBP for step 1 to repeat FOR ONE G3P MOLECULE, THE CALVIN CYCLE CONSUMES NINE ATP AND SIX NADPH, PROVIDED BY THE LIGHT REACTIONS. IT TURNS SIX TIMES TO MAKE ONE GLUCOSE MOLECULE.

  36. What affects photosynthesis? • Water • Shortage of water would slow/stop photosynthesis • Temperature • Enzymes are necessary • Ideal temps (0-35 degrees C) • Light intensity

  37. Why is Photosynthesis Important? • Oxygen • Carbon Dioxide and Moderation of Global Warming • Other?

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