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Photosynthesis

Photosynthesis. STEP Grade 9. Simple Diagram of a Leaf. Cross Section of a Leaf. The Chloroplast. The Chloroplast. Stroma:  The matrix surrounding the grana in the inner membrane of chloroplasts. The area between membranes (thylakoids, grana) inside the chloroplast.

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Photosynthesis

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  1. Photosynthesis STEP Grade 9

  2. Simple Diagram of a Leaf

  3. Cross Section of a Leaf

  4. The Chloroplast

  5. The Chloroplast • Stroma:  The matrix surrounding the grana in the inner membrane of chloroplasts. The area between membranes (thylakoids, grana) inside the chloroplast. • Grana: A series of stacked thylakoid disks containing chlorophyll; found in the inner membrane of chloroplasts.

  6. Chlorophyll

  7. Reactions of Photosynthesis • 6CO2 + 6H2O C6H6O6 + 6O2 • The process is a lot more complex • Actually takes place in two separate stages: • The Light reactions – occurs in grana • The Dark reactions – occurs in stroma

  8. The Light Reactions • The purpose of the light reactions is to change light energy into chemical energy in the form of 2 chemicals ATP and NADPH. • Requires light • Light energy used to make ATP. • The light splits water into hydrogen ions (H+) and oxygen atoms. • The oxygen is released to the air. • The H+ ions are used to make NADPH • ATP carries energy to the dark reactions. • NADPH carries energy and H+ to the dark reactions.

  9. The Dark Reactions • The purpose of the dark reactions is to change CO2 into sugar by adding energy & the H+ ions from ATP & NADPH. • Can occur in light or dark. • 6 CO2 & lots of ATP & NADPH are needed to make one sugar molecule. • The sugar is then used for plant growth or stored for use in fruits and leaves of plants as food for animals

  10. Light & Dark Reactions

  11. Limiting Factors • Factors affecting the rate of photosynthesis. • As the rate of photosynthesis increases so will the plants growth rate. • Three factors limit photosynthesis from going any faster: Light level, carbon dioxide level, and temperature. • Without enough light a plant cannot photosynthesize very fast, even if there is plenty of water and carbon dioxide. Increasing the light intensity will make photosynthesis faster.

  12. Limiting Factors • Sometimes photosynthesis is limited by the level of carbon dioxide. Even if there is plenty of light a plant cannot photosynthesize if it has run out of carbon dioxide. • Temperature can be a limiting factor too. If it gets too cold the rate of photosynthesis will slow right down; equally, plants cease to be able to photosynthesize if it gets

  13. Limiting Factors

  14. Questions • Which graph best shows the effect of increasing light intensity on the rate of photosynthesis? • Which graph best shows the effect of increasing carbon dioxide concentration on the rate of photosynthesis? A • Which graph best shows the effect of increasing temperature if light and carbon dioxide are not limiting (i.e. the levels of light and carbon dioxide are high). A

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