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Photosynthesis

Photosynthesis. Free powerpoints at http://www.worldofteaching.com. Overview. All energy on earth comes from the sun. We depend on: Plants Algae (underwater plants) Cyanobacteria (photosynthetic bacteria) To provide this energy to us!. Overview. Overview.

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Photosynthesis

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  1. Photosynthesis Free powerpoints at http://www.worldofteaching.com

  2. Overview • All energy on earth comes from the sun. • We depend on: • Plants • Algae (underwater plants) • Cyanobacteria (photosynthetic bacteria) • To provide this energy to us!

  3. Overview

  4. Overview • Carbon dioxide and water are taken in by plants • Plants absorb light energy and convert it to a usable form. • ATP • Energy is used to “fix” carbon dioxide into sugar molecules • Chemical energy • Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.

  5. Photosynthesis • Occurs in producers (autotrophs) • These include some bacteria, algae and plants • Occurs in chloroplasts • 6CO2 + 6H2Oenzymes, chlorophyll C6H12O6 + 6O2 light energy

  6. Leaves and Photosynthesis

  7. Chloroplasts • Have TWO membranes • A “bi-bilayer!” • The inner membrane is called the thylakoid. • The thylakoid is folded and looks like stacks of coins called granum (grana singular). • The stroma is the space surrounding the granum Image source: http://www.daviddarling.info/encyclopedia/C/chloroplasts.html

  8. Chloroplasts • Chlorophyll molecules are embedded in the thylakoid membrane • Act like a light “antenna” • These molecules can absorb sunlight energy. Image from Biology 11: College Preparation. Pg 73. Nelson, Toronto. 2003.

  9. Photosynthetic Pigments

  10. Light (dependent)Reactions • Happen ONLY in sunlight • Hence they depend on light! • Light is absorbed by chlorophyll molecules • The energy generates molecules of ATP Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

  11. Light Independent Reactions(formerly the “dark reactions”) • Happen in sunlight, and in the dark. • Hence “independent of light” • ATP generated by sunlight drives the Calvin Cycle. • Monosaccarides (eg. glucose) are manufactured in the cycle. • Monosaccarides are used to “build” polysaccharides (eg. starch). Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.

  12. Overall Reaction What is the equation for photosynthesis? carbon dioxide + water  glucose + oxygen + energy light chlorophyll 6CO2 + 6H2O  C6H12O6 + 6O2 + energy enzymes

  13. Summary

  14. Photosynthesis vs Respiration • Photosynthesis • Occurs in chloroplasts • Uses light to produce high-energy molecules (sugars) • Uses CO2 and H2O • Gives off O2 gas 6CO2 + 6H2O enzymes, chlorophyll C6H12O6 + 6O2 light energy

  15. Cont’d • Respiration: • Occurs in mitochondria • Uses O2 to break down sugars • Releases stored energy to make ATP from ADP • Gives off CO2 and H2O C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP enzymes

  16. Relationship between Photosynthesis and Respiration

  17. Why do leaves turn brown in the fall? • It’s all about pigments! • During the growing season, chlorophyll is continually being produced and broken down and leaves appear green. As night length increases in the autumn, chlorophyll production slows down and then stops and eventually all the chlorophyll is destroyed. The carotenoids and anthocyanins that are present in the leaf are then unmasked and show their colors.

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