Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Photosynthesis

1,893 views

Published on

Published in: Education
  • Be the first to comment

Photosynthesis

  1. 1. Photosynthesis
  2. 3. Photosynthesis <ul><li>Method of converting sun energy into chemical energy usable by cells </li></ul><ul><li>done by autotrophs </li></ul><ul><li>takes place in specialized structures inside plant cells called chloroplasts </li></ul>
  3. 4. <ul><li>Capturing light energy </li></ul><ul><li>Using captured energy to make ATP and NADP + (energy carrying co-enzyme like NAD. It is reduced by 2 H atoms to NADPH + + H + ) </li></ul><ul><li>Using ATP and energy from NADPH to synthesize molecules like glucose. </li></ul><ul><li>first 2 steps require sunlight (light dependant) and occur in chlorophyll </li></ul><ul><li>last step does not necessarily need sunlight (light independent) and takes place in stroma </li></ul>3 Steps of Photosynthesis
  4. 6. Light-Dependent Phases <ul><li>occurs in thylakoid membrane </li></ul><ul><li>light energy converted to chemical energy of ATP & NADPH (reduced NADP = NADPH) </li></ul><ul><li>photosystems (highly organized light capturing complexes) are found in thylakoid membranes and made of 2 parts: </li></ul><ul><ul><ul><li>antenna complex – system of chlorophyll molecules and pigments that transfers energy to reaction centre </li></ul></ul></ul><ul><ul><ul><li>reaction centre – protein complex containing chlorophyll a that absorbs energy from antenna complex and raises it to high energy level to start photosynthesis </li></ul></ul></ul>
  5. 7. <ul><li>there are 2 kinds of photosytems (I and II) depending on which wavelength of light chlorophyll a absorbs </li></ul>
  6. 8. Steps in Light Dependent Reactions <ul><li>Photoexcitation: </li></ul><ul><li>Sunlight hits leaf and some energy passes into stroma then absorbed by antenna complex of photosystem II and passed along to chlorophyll a . </li></ul><ul><li>Electron Transport: </li></ul><ul><li>An electon gets boosted to a higher level and passed along a ETC (like in cellular respiration) in thylakloid membrane. </li></ul><ul><li>This energy boost also causes H 2 O to split which releases H + ions and O 2 which is vital to other living things. </li></ul>
  7. 9. <ul><li>e- passes through several carriers via redox reactions releasing energy as they pass through the proteins. H + ions are pumped from stroma into intermembrane space which creates electrochemical gradient. </li></ul><ul><li>Chemiosmosis: </li></ul><ul><li>H + ions move through ATPase complex back into stroma converting ADP to ATP a process called photophosphorylation . It takes 4 H + to make 1 ATP. </li></ul><ul><li>At same time light of a different wavelength is also striking photosystem 1. e - from P1 pass through another ETC, then move to enzyme NADP reductase that reduces NADP to NADPH which moves to Light Independent Phase . </li></ul>
  8. 10. <ul><li>Reactants: H 2 O, sunlight </li></ul><ul><li>Products: ½ O 2 , NADPH, ATP </li></ul><ul><li>YouTube - Light (Dependant) Reactions of Photosynthesis Animation </li></ul>
  9. 13. 2. Light Independent Reactions (the Calvin Cycle) <ul><li>ATP and NADPH generated in light reactions used to fuel the reactions which take CO 2 and break it apart, then reassemble the carbons into glucose. </li></ul><ul><li>called carbon fixation : taking carbon from an inorganic molecule (atmospheric CO 2 ) and making an organic molecule out of it (glucose) </li></ul><ul><li>occur in stroma </li></ul><ul><li>don’t require light </li></ul><ul><li>also known as C 3 Cycle </li></ul>
  10. 15. Steps in Light Independent Phase: <ul><li>Carbon Fixation </li></ul><ul><li>CO 2 molecule combines with 5C molecule called RuBisCO (ribulose biphosphate) to produce 2, 3C molecules called 3-PGA (3-phosphoglycerate). </li></ul><ul><li>2. Reduction Reactions </li></ul><ul><li>3-PGA phorphorylated by ATP then reduced by NADPH to produce G3P (glycerate 3-phosphate). </li></ul><ul><li>3. RuBisCO Regeneration </li></ul><ul><li>G3P phosphorylated by ATP to re-create RuBisCO to restart the cycle. For every 2 G3P, 1 molecule glucose is removed from cycle, so need 6 CO 2 to create 1 glucose. </li></ul>
  11. 17. Other Methods of Carbon Fixation Succulents, cacti, orchids, pineapple… Water efficiency night CAM Corn, sugar cane, grasses… Faster photosynthesis day C 4 Most plants Uses fewer ATP day C 3 Examples Advantages Stomata open Type of carbon fixation

×