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  1. Photosynthesis RS: Ms. Alvarez CT: Mrs. Rojas

  2. Photosynthesis • Autotrophs (Plants, algae, many bacteria) make organic compounds by photosynthesis. • Chloroplast are the sites of photosynthesis in plants. • Photosynthesis is the process of converting light energy to chemical energy that is stored through the synthesis of sugars. • Plants trap the sun’s energy and build carbohydrates (sugar), called glucose that store energy.

  3. How is photosynthesis divided? • Light reactions • Light-independent reactions / Calvin Cycle/ Dark cycle

  4. Thelight-dependent reaction • This reaction happens in the thylakoid membrane of the chloroplasts. • Light and water are required • Light energy is converted to chemical energy. • ATP, O2 , and NADPH are produced. • oxygen is released into the atmosphere. . • Photosystems have molecules called chlorophylls. • Chlorophylls absorb light.

  5. The light-independent reaction Take place in the stroma of chloroplast. Uses ATP and NADPH to convert CO2 to sugar.

  6. Photosynthesis

  7. Why are leaves green?

  8. Exploring photosynthesis and respiration • In this activity the production of oxygen is used as a measure of the rate of photosynthesis. • Plants need carbon dioxide for photosynthesis. • For this investigation carbon dioxide is provided by a baking soda solution.

  9. Exploring photosynthesis and respiration • This investigation can also allow you to explore cellular respiration through the measurement of oxygen consumption. • Cellular respiration is common to all plants, animals and other organisms which live in an aerobic (with oxygen) environment. • Cellular Respiration is the breakdown of organic compounds by living organisms to obtain energy. • When plants are grown in the light they usually produce more oxygen through photosynthesis than they consume through cellular respiration. • However, when plants are grown in the dark, the trapping of light by photosynthesis can no longer occur, and oxygen is not produced.

  10. Hypothesis Purpose • If leaf discs are placed in light then they will produce _____ and they will____________. • If leaf discs are placed in the dark then they will not produce ___and they will_________. To study and learn the properties of photosynthesis.

  11. Materials • Baking soda + water • Syringe • Spinach leaf • Lamp • straw

  12. Procedure • Using a straw punch out 5 disks from a young spinach leaf. • Pull the plunger out of the syringe. Place the leaf disks into the syringe and replace the plunger. • Draw up 8 ml of baking soda solution into the syringe. Invert the syringe, tip end up, and gently push the plunger to remove all the extra air. • Put your finger over the syringe tip and pull the plunger. This will create a vacuum which will pull the air and oxygen from the leaf discs.

  13. Procedure • Tip the end of the syringe down so that the leaf discs are in the solution. Release plunger; remove your finger. Turn syringe back up and tap the side repeatedly until all of the discs sink. • Place the syringe narrow-end up about 5 cm from the lamp. Record the time. Tap the syringe with your finger every 20-30 seconds to dislodge the floating discs.

  14. Procedure • As the leaf discs photosynthesize and produce oxygen, they will float to the top. Record the time at which each disc floats. • After all discs float, put syringe in the dark. The leaf discs will sink as they respire and consume oxygen. Record the time at which each disc sinks.

  15. Data Calculate the average time. Floating: Sinking:

  16. Conclusion • Summarize the lab activity. • What caused the spinach discs to float when placed under the lamp? • Why did the spinach discs sink when placed in the dark? • Why was baking soda added to the water? • What is photosynthesis?

  17. Conclusion • What is cellular respiration? • What is the formula for photosynthesis? • What factors can affect the rate of photosynthesis? • What type of organisms can undergo photosynthesis?