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Understanding Photosynthesis: Process and Mechanisms Explained

Delve into the intricate process of photosynthesis, from light energy absorption to organic substance production. Explore how sunlight, pigments, and factors like temperature affect the rate of photosynthesis. Learn about chloroplast structure, photoactivation, and chemiosmosis.

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Understanding Photosynthesis: Process and Mechanisms Explained

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  1. PHOTOSYNTHESIS Sun Hwa Dong

  2. Photosynthesis • Produces organic substances • Uses light Energy, Simple inorganic substances • Light Energy to Chemical Energy

  3. Absorption of Light • Sunlight = White light, but made up of wavelengths like red, green, blue • Pigments absorb lights • Red, Blue > Green • Green light cannot be reflected

  4. Absorption of Energy • Some used to produce ATP. • Some split water molecules – Photolysis of Water • This forms Oxygen and Hydrogen.

  5. CO₂ is absorbed to make organic substances. • Carbon in a gas to carbon in solid compounds – Carbon Fixation • This involves use of Hydrogen from photolysis and Energy from ATP.

  6. Measuring Rates of Photosynthesis • Production of O₂ : Aquatic plants release bubbles of O₂ • Uptake of CO₂ :If CO₂ is absorbed from water, the pH of water rises • Increases in biomass : the rate of increase in biomass means more photosynthesis.

  7. Effect of Light Intensity

  8. Effect of CO₂ Concentration • Low light intensity - shortage of ATP and hydrogen

  9. Effect of Temperature • CO₂ fixation is catalyzed by enzymes.

  10. Limiting Factors • Each factors can limit the rate when below optimal level. • Combination of factors – only one factor furthest from its optimum limits • When 2 of the factors are equally close to optimum, increasing them rises the rate.

  11. Action and Absorption Spectra • Action Spectra: % use of wavelengths of light in photosynthesis • Absorption Spectra: % use of the wavelengths of visible light that are absorbed

  12. Photoactivation • Chlorophyll & accessory pigments -Photosystem • Chlorophyll molecules in photosystem absorb light energy and pass it to 2 special chlorophyll molecules in the reaction centre. • Electron within the molecules become excited and photoactivated.

  13. Photophosphorylation • Photophosphorylation: the production of ATP, using E from light which is carried out by thylakoids • Thylakoids: regular “stack” of membranes that contain Photosystem I &Ⅱ, ATP synthase, a chain of electron carriers

  14. Chemiosmosis • Protons pass across membrane and release E which is used by ATP synthase to produce ATP. • The coupling of ATP synthesis to electron transport via a concentration gradient of protons → CHEMIOSMOSIS

  15. Chloroplasts structure • Chloroplast envelop • Thylakoids • Small fluid filled spaces inside Thylakoids • Mostly have stacks of thylakoids called grana • Colorless fluid around Thylakoids = stroma

  16. Bibliography • Course Companion p95-108 • Study Guide p21, p75,p76-81 • Pearson: p 74-78, p227-236 • http://biotransitioneng.wordpress.com/2009/05/10/fossils-fuels-%E2%80%93-a-great-problem/ • http://botit.botany.wisc.edu/images/130/Chlorophyta/Eremosphaera_Images/Chloroplasts_MC.html • Pearson Education, Inc., publishing as Benjamin Cummings • http://www.cbu.edu/~seisen/Photosynthesis.htm • http://helpmyphysics.co.uk/wordpress/?m=200902 • http://botit.botany.wisc.edu/images/130/Chlorophyta/Eremosphaera_Images/Chloroplasts_MC.html • http://generalhorticulture.tamu.edu/lectsupl/physiol/physiol.html • http://fhs-bio-wiki.pbworks.com/Factors-effecting-the-rate-of-photosynthesis • http://reefbuilders.com/2010/08/23/chlorophyll-f-a-newly-discovered-photosynthetic-pigment-uses-infrared-light/ • www.theoremeinnovation.com/revolution-en.html • www.firstrays.com/plants_and_light.htm • http://image.absoluteastronomy.com/images/encyclopediaimages/c/ch/chemiosmosis1.png • www.cbs.dtu.dk/staff/dave/roanoke/bio101ch07.htm • micro.magnet.fsu.edu/.../chloroplasts.html

  17. Vocabulary • Photosynthesis: The process used by plants and other organisms to produce all their own organic substances (food), using only light energy and simple inorganic substances. • Photolysis of water: Splitting of water by energy absorbed by chlorophyll. • Carbon Fixation: The conversion of carbon in a gas to carbon in solid compounds. • Photosystem: protein complexes involved in photosynthesis • Photoactivation: The initial stage of photosynthesis in chlorophyll Molecules where the presence of light Energy raises the energy. • Chemiosmosis: The coupling of ATP synthesis to electron transport via a concentration gradient of protons • Photophosphorylation: the production of ATP, using E from light which is carried out by thylakoids • Thylakoids: regular “stack” of membranes with very small fluid-filled spaces inside that contain Photosystem I &Ⅱ, ATP synthase, a chain of electron carriers • Grana: stacks of thylakoids • Stroma: a colorless fluid around the thylakoids that contains many different enzymes

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