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Photosynthesis

Photosynthesis. Energy & Life. Overview of Photosynthesis. Autotrophs (Producers). Plants and some other types of organisms that contain chlorophyll are able to use light energy from the sun to produce food. Autotrophs. Autotrophs include organisms that make their own food

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Photosynthesis

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  1. Photosynthesis Energy & Life

  2. Overview of Photosynthesis

  3. Autotrophs (Producers) 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. Importance of ATP Principal Compound Used To Store Energy In Living Organisms

  10. 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

  11. 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

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

  13. 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

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

  15. History of Photosynthesis & Plant Pigments

  16. 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

  17. 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?

  18. 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

  19. 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.

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

  21. 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

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

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

  24. 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

  25. The Photosynthesis Equation

  26. 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

  27. Photosynthesis • Where does it take place? • Inside the CHLOROPLAST • Thylakoid membrane • Stacks of these are called granum • Light Reactions happen here • Contains: Chlorophyll (light absorbing/reflecting pigment) • Electrons get excited and start chemical rxns • Stroma • Dark Reactions happen here

  28. 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

  29. 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

  30. Chlorophyll a and b

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

  32. 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

  33. The Biochemical Reactions

  34. It Begins with Sunlight!

  35. Photoautotrophs Absorb Light Energy

  36. Inside A Chloroplast

  37. 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

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

  39. 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

  40. Photosynthesis Overview

  41. 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

  42. Light Dependent Reaction

  43. Light Dependent Reaction

  44. PhotosystemII absorbs light energy Electrons are energized and passed to the Electron Transport Chain Lost electrons are replaced from the splitting of water into 2H+, free electrons, and Oxygen 2H+ pumped across thylakoid membrane Photosynthesis Begins

  45. Photosystem I High-energy electrons are moved to Photosystem I through the Electron Transport Chain Energy is used to transport H+ from stroma to inner thylakoid membrane NADP+ converted to NADPH when it picks up 2 electrons & H+

  46. One more pause for the visual learners...

  47. Chemiosmosis powers ATP synthesis • Energy released during electron flow through the photosystems drives the transport of Hydrogen ions across the thylakoid membrane. • Energy from those electrons is used to make ATP by chemiosmosis • Using the same H+ concentration gradient through the ATP Synthase • During photosynthesis it is known as: Photophosphorylation because it all stated with light from the sun

  48. Chemiosmosis

  49. Let’s Look at That

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