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Photosynthesis

Learn about the process of photosynthesis and how autotrophs convert light energy into food. Explore the history of photosynthesis research and the importance of pigments like chlorophyll.

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Photosynthesis

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  1. Photosynthesis Energy & Life

  2. Overview of Photosynthesis

  3. Autotrophs Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food.

  4. Autotrophs • Autotrophs include organismsthat make their own food • Autotrophs can use the sun’s energy directly Euglena

  5. Heterotrophs • Heterotrophs are organisms that can NOT make their own food • Heterotrophs can NOT directly use the sun’s energy

  6. Energy • Energy Takes Many Forms such as light, heat, electrical, chemical, mechanical • Energy can be changed from one form to another • Energy can be stored in chemical bonds & then released later Candles release energy as HEAT & LIGHT

  7. ATP – Cellular Energy • Adenosine Triphosphate • Contains two, high-energy phosphate bonds • Also contains the nitrogen base adenine & a ribose sugar

  8. ADP • Adenosine Diphosphate • ATP releases energy, a free phosphate, & ADP when cells take energy from ATP One phosphate bond has been removed

  9. Sugar in ADP & ATP • Called ribose • Pentose sugar • Also found on RNA

  10. Importance of ATP Principal Compound Used To Store Energy In Living Organisms

  11. Releasing Energy From ATP • ATP is constantly being used and remade by cells • ATP provides all of the energy for cell activities • The high energy phosphate bonds can be BROKEN to release energy • The process of releasing ATP’s energy & reforming the molecule is called phosphorylation

  12. Releasing Energy From ATP • Adding A Phosphate Group To ADP stores Energy in ATP • Removing A Phosphate Group From ATP Releases Energy & forms ADP Loose Gain

  13. Cells Using Biochemical Energy Cells Use ATP For: • Active transport • Movement • Photosynthesis • Protein Synthesis • Cellular respiration • All other cellular reactions

  14. More on ATP • Cells Have Enough ATP To Last For A Few Seconds • ATP must constantly be made • ATP Transfers Energy Very Well • ATP Is NOT Good At Energy Storage

  15. Glucose • Glucose is a monosaccharide • C6H12O6 • One Molecule of glucose Stores 90 Times More Chemical Energy Than One Molecule of ATP

  16. History of Photosynthesis & Plant Pigments

  17. Photosynthesis • Involves the Use Of light Energy to convert Water (H20) and Carbon Dioxide (CO2) into Oxygen (O2) and High Energy Carbohydrates (sugars, e.g. Glucose) & Starches

  18. Investigating Photosynthesis • Many Scientists Have Contributed To Understanding Photosynthesis • Early Research Focused On The Overall Process • Later Researchers Investigated The Detailed Chemical Pathways

  19. Early Questions on Plants Several Centuries Ago, The Question Was:Does the increase in mass of a plant come from the air? The soil? The Water?

  20. Van Helmont’s Experiment 1643 • Planted a seed into A pre-measured amount of soil and watered for 5 years • Weighed Plant & Soil. Plant Was 75 kg, Soil The Same. • Concluded Mass Came From Water

  21. Priestley’s Experiment 1771 • Burned Candle In Bell Jar Until It Went Out. • Placed Sprig Of Mint In Bell Jar For A Few Days. • Candle Could Be Relit And Burn. • Concluded Plants Released Substance (O2) Necessary For burning.

  22. Ingenhousz’s Experiment 1779 Repeated Priestly experiment with & without sunlight

  23. Results of Ingenhousz’s Experiment • Showed That Priestley’s Results Only Occurred In The Presence Of Sunlight. • Light Was Necessary For Plants To Produce The “Burning Gas” or oxygen

  24. Julius Robert Mayer 1845 Proposed That Plants can Convert Light Energy Into Chemical Energy

  25. Samuel Ruben & Martin Kamen1941 Used Isotopes To Determine That The Oxygen Liberated In Photosynthesis Comes From Water RUBIN KAMEN

  26. Melvin Calvin 1948 • First to trace the path that carbon (CO2) takes in forming Glucose • Does NOT require sunlight • Called the Calvin Cycle or Light Independent Reaction • Also knownas the Dark Reaction

  27. Rudolph Marcus 1992 • Studied the Light Independent Reactions • First to describe the Electron transport Chain

  28. The Photosynthesis Equation

  29. Pigments • In addition to water, carbon dioxide, and light energy, photosynthesis requires Pigments • Chlorophyll is the primary light-absorbing pigment in autotrophs • Chlorophyll is found inside chloroplasts

  30. Light and Pigments • Energy From The Sun Enters Earth’s Biosphere As Photons • Photon = Light Energy Unit • Light Contains A Mixture Of Wavelengths • Different Wavelengths Have Different Colors

  31. Light & Pigments • Different pigments absorb different wavelengths of light • Photons of light “excite” electrons in the plant’s pigments • Excited electrons carry the absorbed energy • Excited electrons move to HIGHER energy levels

  32. Chlorophyll There are 2 main types of chlorophyll molecules: Chlorophyll a Chlorophyll b A third type, chlorophyll c, is found in dinoflagellates Magnesium atom at the center of chlorophyll

  33. Chlorophyll a and b

  34. Chlorophyll a • Found in all plants, algae, & cyanobacteria • Makes photosynthesis possible • Participates directly in the Light Reactions • Can accept energy from chlorophyll b

  35. Chlorophyll b • Chlorophyll b is an accessory pigment • Chlorophyll b acts indirectly in photosynthesis by transferring the light it absorbs to chlorophyll a • Like chlorophyll a, it absorbs red & blue light and REFLECTS GREEN

  36. The Biochemical Reactions

  37. It Begins with Sunlight!

  38. Photoautotrophs Absorb Light Energy

  39. Inside A Chloroplast

  40. Structure of the Chloroplast • Double membrane organelle • Outer membrane smooth • Inner membrane forms stacks of connected sacs called thylakoids • Thylakoid stack is called the granun (grana-plural) • Gel-like material around grana called stroma

  41. Function of the Stroma • Light Independent reactions occur here • ATP used to make carbohydrates like glucose • Location of the Calvin Cycle

  42. Thylakoid membranes • Light Dependent reactions occur here • Photosystems are made up of clusters of chlorophyll molecules • Photosystems are embedded in the thylakoid membranes • The two photosystems are: Photosytem I Photosystem II

  43. Photosynthesis Overview

  44. Energy Carriers • Nicotinamide Adenine Dinucleotide Phosphate (NADP+) • NADP+ = Reduced Form • Picks Up 2 high-energy electrons and H+from the Light Reaction to form NADPH • NADPH carries energy to be passed on to another molecule

  45. NADPH

  46. Light Dependent Reactions • Occurs across the thylakoid membranes • Uses light energy • Produce Oxygen from water • Convert ADP to ATP • Also convert NADP+ into the energy carrier NADPH

  47. Light Dependent Reaction

  48. Light Dependent Reaction

  49. Photosystem I • Discovered First • Active in the final stage of the Light Dependent Reaction • Made of 300 molecules of Chlorophyll • Almost completely chlorophyll a

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