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PHOTOSYNTHESIS

Explore the wonders of photosynthesis, the process where plants convert sunlight into energy, revealing the science behind why plants are green and the magic of light reactions and the Calvin Cycle.

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PHOTOSYNTHESIS

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  1. PHOTOSYNTHESIS 6.1

  2. The main form of energy from the sun is in the form of electromagnetic radiation • Visible radiation (white light) used for photosynthesis • Remember : ROY G. BIV?

  3. The electromagnetic spectrum

  4. A Red Object absorbs the blue and green wavelengths and reflects the red wavelengths

  5. Why are plants green?

  6. pigment a compound that absorbs light • different pigments absorb different wavelengths of white light. • chlorophyll is a pigment that absorbs red & blue light (photons) so green is reflected or transmitted. • Chlorophyll is located in the thylakoidmembranes So, Plants are green because the green wavelength is reflected, not absorbed.

  7. 2 types of chlorophyll • Chlorophyll a – involved in light reactions • Chlorophyll b – assists in capturing light energy – accessory pigment • Carotenoids – accessory pigments – captures more light energy • Red, orange & yellow

  8. The electromagnetic wavelengths and the wavelengths that are absorbed by the chlorophyll

  9. During the fall, what causes the leaves to change colors?

  10. Fall Colors • In addition to the chlorophyll pigments, there are other pigments present • During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments • Carotenoids are pigments that are either red, orange, or yellow

  11. Photosynthesis is - • conversion of light energy into chemical energy that is stored in organic compounds (carbohydrates > glucose) • Used by autotrophs such as: • Plants • Algae • Some bacteria (prokaryotes)

  12. (carbohydrate) • glucose - energy-rich chemical produced through photosynthesis • C6H12O6 • Biochemical pathway – series of reactions where the product of one reaction is consumed in the next • E.g. photosynthesis product is glucose which is used in cellular respiration to make ATP

  13. Photosynthesis equation Light energy 6CO2 + 6H2O C6H12O6 + 6O2 Chlorophyll Reactants: Carbon dioxide and water Products: glucose and oxygen which is a byproduct

  14. Where does photosynthesis take place?

  15. Chloroplast Mesophyll Cell Stoma Plants • Mainly occurs in the leaves: a. stoma - pores b. mesophyll cells

  16. Nucleus Cell Wall Chloroplast Central Vacuole Mesophyll Cell of Leaf Photosynthesis occurs in these cells!

  17. Oxygen (O2) Carbon Dioxide (CO2) Guard Cell Guard Cell Stomata (stoma) Pores in a plant’s cuticle through which water vapor and gases(CO2 & O2) are exchanged between the plant and the atmosphere. Stoma Found on the underside of leaves

  18. Stroma Outer Membrane Thylakoid Granum Inner Membrane Chloroplast Organelle where photosynthesistakes place. Thylakoid stacks are connected together

  19. Parts • chloroplasts – dbl membrane organelle that absorbs light energy • Thylakoids – flattened sacs contain pigment - chlorophyll • Grana (pl: granum) – layered thylakoids (like pancakes) • Stroma – solution around thylakoids • Stomata – pore on underside of leaf where O2 is released and CO2 enters • Stroma : chloroplast :: cytosol : cytoplasm

  20. Thylakoid Membrane Thylakoid Space Granum Thylakoid Grana make up the inner membrane

  21. What do cells use for energy?

  22. Energy for Life on Earth • Sunlight is the ULTIMATE energy for all life on Earth • Plants store energy in the chemical bonds of sugars • Chemical energy is released as ATP during cellular respiration

  23. Structure of ATP • ATP stands for adenosine triphosphate • It is composed of the nitrogen base ADENINE, the pentose (5C) sugar RIBOSE, and three PHOSPHATE groups • The LAST phosphate group is bonded with a HIGH ENERGY chemical bond • This bond can be BROKEN to release ENERGY for CELLS to use

  24. Removing a Phosphate from ATP Breaking the LAST PHOSPHATE bond from ATP, will --- • Release ENERGY for cells to use • Form ADP (adenosine diphosphate) • Produce a FREE PHOSPHATE GROUP

  25. High Energy Phosphate Bond

  26. FREE PHOSPHATE can be re-attached to ADP reforming ATP Process called Phosphorylation

  27. Phosphorylation

  28. Photosynthesis SUN 1. Light Reaction - Produces energy from solar power (photons) in the form of ATP and NADPH. 2. Calvin Cycle • Also called Carbon Fixation or Carbon Cycle, Uses energy (ATP and NADPH) from light reaction to make sugar (glucose).

  29. 3 stages of photosynthesis-

  30. Stages: • STAGE 1 - LIGHT REACTIONS - energy from sun is used to split water into H+ an O2 • STAGE 2 – energy is converted to chemical energy & stored in ATP & NADPH in stroma • STAGE 3 - CALVIN CYCLE where carbon is fixed into glucose

  31. Light Reaction (Electron Flow) • Occurs in the Thylakoid membranes • 2 possible routes for electron flow: Use Photosystem I and Electron Transport Chain (ETC) and generate ATP only • OR use Photosystem II and Photosystem I with ETC and generate O2, ATP and NADPH

  32. Photosynthesis animation • http://www.mhhe.com/biosci/genbio/biolink/j_explorations/ch09expl.htm

  33. ELECTRON TRANSPORT - LIGHT REACTIONS in 5 steps

  34. Photosystem I and II • Step 1 – light excites e- in photosystem II • Step 2 – e- move to primary e- acceptor Step 3 – e- move along electron transport chain (etc) • Step 4 – light excites e- in photosystem I • Step 5 – e- move along 2nd (etc) • End – NADP+ combine H+ to make NADPH

  35. Light reaction animation • http://www.science.smith.edu/departments/Biology/Bio231/ltrxn.html

  36. Electron transport chain song • Play the "Come On Down (The Electron Transport Chain)" song performed by Sam Reid. 

  37. Photolysis –photo-chemical splitting of water (restoring photosystem II)

  38. Chemiosmosis – synthesis of ATP • Powers ATP synthesis • Takes place across the thylakoid membrane • Uses ETC and ATP synthase • H+ move down their concentration gradient forming ATP from ADP • Concentration of protons is greater in thylakoid than stroma

  39. SUN (Proton Pumping) H+ H+ Thylakoid E T PS I PS II C high H+ concentration H+ H+ H+ H+ H+ H+ Thylakoid Space H+ ATP Synthase low H+ concentration ADP + P ATP H+ Chemiosmosis

  40. The Calvin Cycle 6.2

  41. Calvin Cycle - • Biochemical pathway in photosynthesis that produces organic compounds using ATP & NADPH • Carbon fixation – carbon atoms from CO2 are bonded or ‘fixed’ into carbohydrates • occurs in stroma

  42. Calvin Cycle • Carbon Fixation • C3 plants (80% of plants on earth) • Occurs in the stroma • Uses ATP and NADPH from light reaction as energy • Uses CO2 • To produce glucose: it takes 6 turns and uses 18 ATP and 12 NADPH.

  43. STROMA– where Calvin Cycle occurs Outer Membrane Thylakoid Granum Inner Membrane Chloroplast

  44. (36C) (6C) 6C-C-C-C-C-C (unstable) 6CO2 6C-C-C 6C-C-C 12PGA (36C) 6ATP 6ATP (30C) 6C-C-C-C-C 6NADPH 6NADPH RuBP (36C) 6C-C-C 6C-C-C 6ATP 12G3P (30C) (6C) C3 C-C-C-C-C-C Glucose glucose Calvin Cycle (C3 fixation)

  45. C3 Glucose Calvin Cycle Remember: C3 = Calvin Cycle

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