1. Photosynthesis in Detail A Look Into the Future It is 100 years in the future and you are a research scientist. An enormous volcanic eruption has recently sent huge quantities of dust and ash into the atmosphere. Working with a partner, make a list of how this event will affect each of the following: 1. photosynthesis 2. plant life 3. animal life 4. human societies Section 8-3 Interest Grabber Go to Section:

2. Photosynthesis in Detail 8–3The Reactions of Photosynthesis A.Inside a Chloroplast B.NADPH C.Light-Dependent Reactions D.The Calvin Cycle E.Factors Affecting Photosynthesis Section 8-3 Section Outline Go to Section:

3. Photosynthesis in Detail Photosynthesis Process that captures the sun’s energy to convert water and carbon dioxide into sugars and oxygen. This is an energy absorbing reaction. 3 sunlight 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 chlorophyll

4. Photosynthesis in Detail It may be the most important chemical reaction on our planet. 1.Life on earth runs on solar power! Most of our food comes directly or indirectly from the sun through photosynthesis. 2.Also, oxygen is released into the air by plants through photosynthesis. Why is photosynthesis important?

5. Photosynthesis in Detail How do cells use the products of photosynthesis? Once sunlight energy is changed into chemical energy by photosynthesis, organisms must change the chemical energy in glucose into ATP, a form that can be used by cells. What is this process? Cellular Respiration!

6. Photosynthesis in Detail Respiration is almost the exact opposite reaction to photosynthesis. The products of one reaction are the reactants for the other, with energy from the sun driving the whole cycle. Photosynthesis: 6CO 2 + 6H 2 O + Energy C 6 H 12 O 6 + O 2 Respiration: C 6 H 12 O 6 + O 2 6CO 2 + 6H 2 O + Energy Linking Photosynthesis & Respiration

7. Photosynthesis in Detail Photosynthesis and cell respiration work together to solar power living things and recycle carbon.

8. Photosynthesis in Detail Where does photosynthesis take place? In plants, in the chloroplasts of leaf and green stem cells What are thylakoids? A photosynthetic membrane in the chloroplast. It contains clusters of chlorophyll and a protein (photosystems) that will capture the light energy from the sun. Grana – stacks of thylakoid membranes Stroma: The Region outside of the thylakoid membranes

9. Photosynthesis in Detail Photosynthesis occurs in chloroplasts of leaf cells. 9 Leaf tissue Leaf cell Chloroplast (organelle)

10. Photosynthesis in Detail

11. Chloroplasts All the pigments and enzymes for the light reaction are close together on the thylakoids membranes. Nearby, the stroma has the enzymes and reactants for the light-independent reactions.

12. Photosynthesis in Detail sunlight 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 chloroplasts **Photosynthesis is actually 2 sets of reactions: 1.light dependent reaction catches energy from the sun and transfers it to the: 2.light independent reaction which stores the energy in glucose

13. Photosynthesis in Detail KEY CONCEPT Photosynthesis requires a series of chemical reactions.

14. Photosynthesis in Detail The first stage of photosynthesis captures and transfers energy. The light-dependent reactions include groups of molecules called photosystems.

15. Photosynthesis in Detail **Photosystems (Proteins) groups of pigments that act like antennae to focus light energy towards a special reactor chlorophyll molecule in the middle. This really excites the electrons of the reactor molecule, boosting them to higher energy levels.

16. Photosynthesis in Detail Photosystems 16 e-e- e-e- Other Pigments Light

17. Photosynthesis in Detail Two Photosystems Photosystem II discovered second, but first one activated in the light reaction Group of pigments with reactor chlorophyll called p700 (because absorbs best at wavelength 700) Photosystem I discovered first, activated second group of pigments with p680 reactor chlorophyll at the center (because absorbs best at wavelength p680)

18. Photosynthesis in Detail **Photosystem II captures and transfers energy. –chlorophyll absorbs energy from sunlight –energized electrons enter electron transport chain –water molecules are split –oxygen is released as waste –hydrogen ions are transported across thylakoid membrane

19. Photosynthesis in Detail During photosynthesis electrons are super excited, the electrons then are transported to the area they are needed. The electrons must be handled by a carrier molecule **NADP: A Carrier molecule, it holds 2 electrons + 1 hydrogen and forms NADPH storing the electrons for transport to other parts of the cell. Used to produce glucose

20. Photosynthesis in Detail **Photosystem I captures energy and produces energy- carrying molecules. –chlorophyll absorbs energy from sunlight –energized electrons are used to make NADPH –NADPH is transferred to light- independent reactions

21. Photosynthesis in Detail Light Dependent Reactions 1.Capturing light from the sun A.Light is absorbed by pigments in photosystem II and excites 2 electrons, boosting them to higher energy levels B.2 electrons and their energy are carried from Photosystem II to Photosystem I along an electron transport chain. C.Then light is absorbed by pigments in photosystem II D.This excites photosytem II’s electrons & boosts them to higher energy levels. (uses molecules stuck in the thylakoid membrane)

22. Photosynthesis in Detail Light Dependent Reactions 1.Capturing light from the sun A.2 electrons in Phososystem II are so energized that they escape B.They are like hot (energized) potatoes in the cell. C.They are received by the carrier molecule NADP+

23. Photosynthesis in Detail Light Dependent Reactions 2. Split water molecules to form O 2 Electrons lost by Photosystem II need to be replaced! They are taken from nearby water molecules in an enzyme reaction that splits water into O 2, H + and electrons This is where the O 2 comes from in photosynthesis!

24. Photosynthesis in Detail The light-dependent reactions produce ATP. –hydrogen ions flow through a channel in the thylakoid membrane –**ATP synthase attached to the channel makes ATP

25. Photosynthesis in Detail Light Dependent Reactions 3. Form ATP and NADPH NADP + took H+ from splitting water and 2 electrons from Photosystem I NADPH ATP is made on ATP synthase embedded in the thylakoid membrane Electrons moving in the electron transport chain, pump protons into the thylakoid space. When protons diffuse back through ATP synthase, ADP is phosphorylated to ATP

26. Photosynthesis in Detail H 2 O H 2 O 1/2 O 2 + 2e - +2H + Electron transport chain

27. Photosynthesis in Detail Light Dependent Reactions Produces: 1.Oxygen (O 2 ) 2.ATP 3.NADPH Requires: water, sunlight & chloroplasts with photosystems (chlorophyll), enzymes, energy carriers

28. Photosynthesis in Detail Light Dependent Reactions

29. Photosynthesis in Detail Photosynthesis Overview Light Dependent Reactions 1.Capture energy from sunlight 2.Split water molecules to form O 2 3.Form ATP & NADPH (energy carrier) Light Independent Reactions 1.Use ATP and NADPH from the light dependent reaction to make sugars from CO 2 29 IMPORTANT SLIDE – KNOW THIS!!

30. Photosynthesis in Detail Light-independent reactions occur in the stroma and use CO 2 molecules. The second stage of photosynthesis uses energy from the first stage to make sugars.

31. Photosynthesis in Detail Light Independent Reactions Use ATP and NADPH from the light dependent reaction to make sugars from CO 2 also called dark reaction or Calvin cycle, because does not need light usually occurs during the day but can occur at night if CO 2, ATP and NADPH are available. occurs in the stroma of the chloroplast

32. Photosynthesis in Detail **Calvin Cycle Light Independent Used to develop high energy sugars. CO2 enters cycle: combines with other carbons to make 12, 3-carbon molecules Energy Input: Energy from ATP and NADPH create high energy bonds in the carbon molecules.

33. Photosynthesis in Detail **Calvin Cycle 6 Carbon Sugar: 3 carbon molecules are converted into 6 Carbon sugars 5-Carbon molecules Regenerated: the left over Carbon molecules are formed into 5 carbon chains to reenter the cycle.

34. Photosynthesis in Detail **Light Independent Cycle http://student.ccbcmd.edu/~gkaiser/biotutorials/photosyn/images/u4fg46.jpg CO 2 from the air is combined using enzymes through this cycle to produce sugars. It takes 6 turns with 6CO 2 and uses 18 ATP and 12 NADPH to produce one glucose molecule.

35. Photosynthesis in Detail **Light Independent Reactions Produces: glucose Requires: CO2, plus ATP & NADPH from the light reaction and enzymes

36. Photosynthesis in Detail Photosynthesis includes of take place in takes place in uses to produce use Light- dependent reactions Calvin cycle Thylakoid membranes StromaNADPH ATP Energy from sunlight ATPNADPHO2O2 Chloroplasts High-energy sugars Section 8-3 Concept Map Go to Section:

37. Photosynthesis in Detail Energy travels to earth from the sun in waves that act like light packets of energy. Sunlight (white light) is a mix of different wavelengths with different energy. Shorter wavelengths (ultraviolet) have more energy. Light we see is light that is reflected from an object’s surface because it is not absorbed. Short waveLong wave (more energy)(less energy)

38. Photosynthesis in Detail Chlorophyll Pigments Because light is a form of energy, any molecule that absorbs light also absorbs energy = its electrons get excited. Pigments - molecules that absorb certain wavelengths and reflect certain wavelengths (what we see as color!) Plants gather energy using light absorbing pigments Chlorophyll a & b are the main light capturing pigments in plants.

39. Photosynthesis in Detail Chlorophyll Absorbtion Chlorophyll a & b absorb light in the blue and red regions of the spectrum and reflect green Why are plants green?

40. Photosynthesis in Detail Carotenoids Other light absorbing pigments that capture different wavelengths of light Usually red, yellow, orange Seen in the fall when less chlorophyll present. Part of the photosystems

41. Photosynthesis in Detail 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 C 6 H 12 O 6 Carbons and oxygen in sugars come from CO 2 Oxygen released by plants comes from splitting water Photosynthesis – tracking molecules

42. Photosynthesis in Detail Summary of Photosynthesis

43. Photosynthesis in Detail

44. Factors that affect the rate of photosynthesis Light - Low quantity or wrong wavelength light = less photosynthesis Temperature – enzyme catalyzed reactions = optimum temperature CO 2 - Low CO 2 = less photosynthesis Water - Low water for splitting, and can cause leaf pores to close, so CO 2 cannot diffuse into the leaves.