How do photosynthesis occurs in plants.pptx

This slide explain the photosynthesis process in plants.

1. Photosynthesis: Life from Light and Air

2. PHOTO // SYNTHESIS

3. Photosynthesis is the process by autotrophic organisms that use light energy, carbon dioxide and water to make sugar and oxygen gas PHOTOSYNTHESIS

4. PHOTOSYNTHESIS 6 CO 2 + 6 H 2 O + light energy → C 6 H 12 O 6 + 6 O 2 (Carbon dioxide) (water) (glucose) (oxygen)

5. Organisms that use light energy from the sun to produce food— autotrophs (auto = self) Ex: plants and some microorganisms (some bacteria and protists)

6. Organisms that CANNOT use the sun’s energy to make food— heterotrophs Ex: animals and most microorganisms

7. Photosynthesis: Photosynthesis is the process by which the energy of sunlight is converted into the energy of glucose

8. Chloroplasts double membrane stroma fluid-filled interior thylakoid sacs grana stacks Thylakoid membrane contains chlorophyll molecules electron transport chain ATP synthase H + gradient built up within thylakoid sac Plant structure H + H + H + H + H + H + H + H + H + H + H + outer membrane inner membrane thylakoid granum stroma thylakoid chloroplast ATP

9. Chloroplast Organelle where photosynthesis takes place. Granum Thylakoid Stroma Outer Membrane Inner Membrane

10. Thylakoid Thylakoid Membrane Thylakoid Space Granum

11. Why is Photosynthesis important? Makes organic molecules (glucose) out of inorganic materials (carbon dioxide and water). It begins all food chains/webs. Thus all life is supported by this process. It also makes oxygen gas!!

12. Photosynthesis -starts ecological food webs!

13. PHOTOSYNTHESIS Absorbing Light Energy to make chemical energy: glucose! Pigments: Absorb different colors of white light (ROY G BIV) Main pigment: Chlorophyll a Accessory pigments: Chlorophyll b and Carotenoids These pigments absorb all wavelengths (light) BUT green!

14. Chlorophyll a Chlorophyll b Carotenoids Xanthophyll Chloroplasts contain several pigments

15. Why do we see green? Green color from white light reflected NOT absorbed Chloroplast: organelle responsible for photosynthesis Chlorophyll: located within Chloroplast Green pigment

16. Light: absorption spectra Photosynthesis gets energy by absorbing wavelengths of light chlorophyll a absorbs best in red & blue wavelengths & least in green accessory pigments with different structures absorb light of different wavelengths chlorophyll b, carotenoids, xanthophylls Why are plants green?

17. violet blue green yellow orange red

18. Chlorophyll Molecules Located in the thylakoid membranes . Chlorophyll have Mg + in the center. Chlorophyll pigments harvest energy (photons) by absorbing certain wavelengths ( blue-420 nm and red-660 nm are most important). Plants are green because the green wavelength is reflected , not absorbed .

19. Plants Leaves are green because they contain the pigment: chlorophyll Leaves have a large surface area to absorb as much light as possible

20. What happens during photosynthesis? Plants capture light energy and use that energy to make glucose Sunlight provides the energy needed by chlorophyll to change molecules of carbon dioxide and water into glucose Oxygen is also released in this reaction

21. Photosynthesis

22. Photosynthesis: An Overview The net overall equation for photosynthesis is: Photosynthesis occurs in 2 “ stages ” : The Light Reactions (or Light-Dependent Reactions) The Calvin Cycle (or Light-Independent Reactions) 27 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 light

23. Photosynthesis Light reactions light-dependent reactions energy conversion reactions convert solar energy to chemical energy ATP & NADPH Calvin cycle light-independent reactions sugar building reactions uses chemical energy (ATP & NADPH) to reduce CO 2 & synthesize C 6 H 12 O 6

24. Light Reactions O 2 H 2 O Energy Building Reactions ATP produces ATP produces NADPH releases O 2 as a waste product sunlight H 2 O ATP O 2 light energy  + + + NADPH NADPH

25. H + H + ATP Synthase H + H + H + H + H + H + high H + concentration H + ADP + P ATP PS II PS I E T C low H + concentration H + Thylakoid Space Thylakoid SUN (Proton Pumping)

26. Calvin Cycle sugars CO 2 Sugar Building Reactions ADP builds sugars uses ATP & NADPH recycles ADP & NADP back to make more ATP & NADPH ATP NADPH NADP CO 2 C 6 H 12 O 6  + + + NADP ATP + NADPH ADP

27. Putting it all together CO 2 H 2 O C 6 H 12 O 6 O 2 light energy  + + + Sugar Building Reactions Energy Building Reactions Plants make both: energy ATP & NADPH sugars sunlight O 2 H 2 O sugars CO 2 ADP ATP NADPH NADP

28. Photosynthesis summary Light reactions produced ATP produced NADPH consumed H 2 O produced O 2 as byproduct Calvin cycle consumed CO 2 produced G3P (sugar) regenerated ADP regenerated NADP NADP ADP

29. Different Carbon-Fixing Pathways Environments differ, and so do details of photosynthesis C3 plants C4 plants CAM plants

30. Stomata Stomata () Small openings through the waxy cuticle covering epidermal surfaces of leaves and green stems Allow CO 2 in and O 2 out Close on dry days to minimize water loss

31. C3 Plants C3 plants Plants that use only the Calvin–Benson cycle to fix carbon Forms 3-carbon PGA in mesophyll cells Used by most plants, but inefficient in dry weather when stomata are closed

32. Photorespiration When stomata are closed, CO 2 needed for light-independent reactions can’t enter, O 2 produced by light-dependent reactions can’t leave Photorespiration At high O 2 levels, rubisco attaches to oxygen instead of carbon CO 2 is produced rather than fixed

33. C4 Plants C4 plants Plants that have an additional set of reactions for sugar production on dry days when stomata are closed ; compensates for inefficiency of rubisco Forms 4-carbon oxaloacetate in mesophyll cells, then bundle-sheath cells make sugar Examples: Corn, switchgrass, bamboo

34. C3 and C4 Plant Leaves

35. CAM Plants CAM plants (Crassulacean Acid Metabolism) Plants with an alternative carbon-fixing pathway that allows them to conserve water in climates where days are hot Forms 4-carbon oxaloacetate at night, which is later broken down to CO 2 for sugar production Example: succulents, cactuses

36. Fig. 7-13a, p. 117 C3

37. Fig. 7-13b, p. 117 C4

38. Fig. 7-13c, p. 117 CAM

39. A CAM Plant Jade plant ( Crassula argentea )

40. FACTORS AFFECTING THE RATE OF PHOTOSYNTHESIS :

41. 1) LIGHT As light intensity increases, the rate of photosynthesis initially increases, and thereafter, levels off to a plateau.

42. This plateau represents the maximum rate of photosynthesis ---as seen in the diagram. Higher light intensity initially causes more electrons in the chlorophyll molecules to become excited (gain energy). Modern Biology (Holt)

43. As more and more electrons are excited, the light reactions occur more rapidly. At a certain light intensity , however, all the available electrons are excited and a further increase in light intensity will not increase the rate of photosynthesis. Modern Biology (Holt)

44. 2) Carbon dioxide Like increasing light intensity, increasing levels of carbon dioxide around the plant stimulates photosynthesis until it reaches a plateau. This graph would resemble that of light intensity. Modern Biology (Holt)

45. 3 ) Temperature a) Raising the temperature accelerates various chemical reactions of photosynthesis. As a result, the rate of photosynthesis increases , over a certain range. Modern Biology (Holt)

46. b) The rate of photosynthesis generally peaks at a certain temperature , as seen in the graph. c) Above this temperature, the rate decreases .

47. Why is temperature important? The light-independent reaction of photosynthesis is controlled by enzymes . Temperature affects enzyme reactions. As temperature increases, collision frequency between reactant particles and between reactant and enzyme increases. This increases the rate of reaction up to the optimum temperature. Beyond the optimum temperature however, enzymes begin to be denatured . Their tertiary structure breaks down, changing the shape of the active site so that reactant molecules no longer fit. up to optimum temperature enzyme denatured at high temperature

48. d) As the temperature increases, the stomates begin to close , to limit water loss. This will have the effect of stopping the carbon dioxide from entering the leaf. This will also decrease the rate of photosynthesis . (Also: Enzymes do not function well at too high a temperature.)

49. 4) Water A lack of water will also slow the rate of photosynthesis. Stomata can close from water loss . Plants such as the cactus have adaptations to prevent water loss in dry, desert climates .