What is Photosynthesis?

1. What is Photosynthesis? • Photosynthesis is a biochemical process.

2. What is Photosynthesis? • Plants absorb light from the sun. • They convert this solar or radiantenergy into stored chemicalenergy.

3. Chlorophyll. • Photosynthesis takes place in greenpigmentscalled chlorophyll. Chlorophyll is a molecule

4. Chloroplasts • The green pigments known as chlorophyll are found in chloroplasts. Chloroplasts are organelles

5. Chloroplasts • Chloroplasts are bound by a membrane.

6. Stroma • A fluid-filled region within the chloroplast is known as the stroma.

7. The stroma is filled with fluid

8. Very Important • The stroma contains most of theenzymes required for photosynthetic reactions.

9. Thylakoids • Also inside the chloroplast is a system of membranes that form an interconnected set of flat, disk-like sacs referred to as the thylakoids.

10. Thylakoids • The thylakoid sacs are arranged in stacks, similar in appearance to a stack of coins.

11. Thylakoid and Coins

12. Grana • These stacks are called grana

13. Grana = Stacks of Thylakoids

14. Chlorophyll • Chlorophyll is a complex molecule that is the main pigment of photosynthesis.

15. Chlorophyll • Chlorophyll has two primary forms.

16. Chlorophyll a • The most important is chlorophyll a.

17. Chlorophyll a • Chlorophyll a is bright green and is responsible for absorbing energy from the violet-blue to red and red-orange light wavelengths.

18. Chlorophyll a • Chlorophyll a initiates the light-dependent reactions in the photosynthetic process.

19. Chlorophyll b • Chlorophyll b is yellow-green and absorbs wavelengths of light slightly different from chlorophyll a.

20. Carotenoids • Carotenoids are additional pigment • yellow and orange in color that • absorb energy from green-yellow-orange wavelengths.

21. Carotenoids • The energy absorbed by carotenoids can be transferred to chlorophyll a.

23. Photosynthesis 1-2-3 • Plants convert light energy into chemical energy stored in glucose molecules through the process of photosynthesis.

24. Photosynthesis 1-2-3 • Chlorophyll traps light energy from sunlight.

25. Photosynthesis 1-2-3 • It uses the this energy to manufacture the high-energy compounds ATP and NADPH.

26. Photosynthesis 1-2-3 Plants use the energy held in the ATP and NADPH molecules to make carbohydrates. .

27. Photosynthesis 1-2-3 • Sugars, starches, and cellulose are carbohydrates

28. Photosynthesis 1-2-3 • Sugars and starches serve as energy sources for cells.

29. Photosynthesis 1-2-3 • Cellulose is the main structural component of walls that surround plant cells.

31. The Reactions • Photosynthesis has two main reactions.

32. Light-dependent Reactions • The first is the light-dependent reaction.

33. Light-dependent Reactions • The light-dependent reaction only occurs in the presence of light.

34. Light-dependent Reactions • Chlorophyll absorbs the light energy.

35. Light-dependent Reactions • The light energy is converted to electricalenergy.

36. Light-dependent Reactions • Some of the electrical energy is used to make ATP through a process known as photophosphorylation. • Some of the light energy trapped by the chlorophyll is used to split water molecules. • Oxygen from the water is released. • Hydrogen atoms from the water combine with NADP to form NADPH.

37. Light-independent Reactions • The light-independent reaction does not requirelight. • It is sometimes referred to as the dark reaction. • In this reaction ATP and NADPH, formed during the light-dependent reaction, are used to make high-energy carbohydrates.

38. Light-independent Reactions • The carbohydrates function as a good long-term energy storage system. • What happens to tree sap in the fall? • The materials used in the process include carbon dioxide from the air and hydrogen from the NADPH. • Remember this hydrogen was originally obtained from water.

39. Light-independent Reactions • Most plants use the Calvin cycle to fix carbon during the light-independent reaction. • The Calvin cycletakes place in the stroma within mesophyll cells. • Initially a six-carbon molecule is formed. • Instantly, it splits into 2 three-carbon molecules.

40. Light-independent Reactions • The three-carbon molecules join to form the simple sugars, glucose, and fructose. • It takes six turns of the Calvin cycle, involving the input of six carbon dioxide molecules, hydrogen from NADPH plus ATP, to result in one molecule of glucose.

41. What Factors Affect Photosynthesis? • Outside factors influence the rate of photosynthesis. • The first requirement for photosynthesis is a healthy, living, green plant or other photosynthetic organism.

42. What Factors Affect Photosynthesis? • There must be an ample supply of carbon dioxide in the atmosphere. • Higher levels of carbon dioxideresult in more rapid growth. • In some greenhouses, carbon dioxide is added to the atmosphere to speed photosynthesis and plant growth.

43. What Factors Affect Photosynthesis? • Watermust be available for plant use. • Severe lack of water results in wilting or a limp appearance to the plant. • Stamatas close to conserve water. • Carbon dioxide levels in the leaf drop, and photosynthesis shuts down.

44. What Factors Affect Photosynthesis? • Light or radiant energy drives photosynthesis. • Photosynthesis cannot occur without light.

45. What Factors Affect Photosynthesis? • Temperature is also important. • As with all enzymes, the enzymes involved in photosynthesis work in a narrow temperature range.