Remember!

1. Remember! • ADP vs. ATP • How is glucose related to ATP & energy?

2. Remember! • Plants are autotrophs, which means they do NOT have to consume other organisms for food. So where do plants get their food & energy?

3. Photosynthesis

4. Photosynthesis • The process in which plants use solar energy to convert water & carbon dioxide into high-energy carbohydrates (sugars & starches) & oxygen (a waste product)

5. Photosynthesis • Photosynthesis occurs in chloroplasts! • Mostly in the leaves

6. The Photosynthesis Equation Reactants  Products 6CO2 + 6H2O + Light  C6H12O6 + 6O2 Carbon Dioxide + Water + Light  Sugars + Oxygen

7. Plants get their CO2 from the water or air they live in. The roots of the plant soak of water from the soil. Sunlight provides the energy to convert the water & CO2 into sugars & oxygen!

9. Light & Pigments • Photosynthesis requires: • Water • Carbon Dioxide • Light • Chlorophyll – a pigment molecule in chloroplasts; 2 types: • Chlorophyll A • Chlorophyll B

10. ROYGBIVRed-Orange-Yellow-Green-Blue-Indigo-Violet • Sunlight is perceived as white light, but is really a mixture of different wavelengths of light (like a rainbow)! • The visible light we can see is a very small portion of the electromagnetic spectrum. Red: long wavelength; less energy Violet: short wavelength; high energy

11. Pigments • Molecules that absorb light at different wavelengths • Chlorophyll absorbs light in the visible spectrum, except the green wavelengths. • Green light is reflected by the leaves, making plants look green! The high energy that is absorbed makes photosynthesis work!

12. Factors that Affect Photosynthesis • Shortage of water • Temperature • Intensity of light The optimum temperature for photosynthesis is 20-25 degrees Celsius (about room temperature)!

13. How does UV light affect the rate of photosynthesis? • Materials available: • Elodea • Baking Soda (NaHCO3) • Water • UV Lamp • Beakers, test tubes, graduated cylinders, etc. • Question • Hypothesis • Materials • Procedure • Data & Results • Conclusion

14. Photosynthesis occurs inside chloroplasts! • Chloroplasts contain: • Thylakoids: sac-like photosynthetic membranes containing pigments • Grana (singular “granum”): stacks of thylakoids • Stroma: region of chloroplasts outside of the thylakoid membranes • Inner Membrane • Outer Membrane

15. Electron Carriers • Sunlight excites electrons in chlorophyll, causing them to gain energy. • An excited electron is like a hot coal & cannot easily be carried from 1 place to another! • A protein, an electron carrier, is required to transport excited electrons.

16. Electron Carriers • Electron Transport: an electron carrier protein can accept a pair of high-energy electrons & transfer them to another molecule • Electron Transport Chain: series of electron carriers • Example: NADP+ (nicotinamide adenine dinucleotide phosphate) NADP+ + 2 electrons + H+ NADPH NADPH can carry high-energy electrons to other chemical reactions in the cell that need energy!

17. Photosynthesis • Photosynthesis can be broken down into 2 parts: • Light Dependent Reactions • Light Independent Reactions (The Calvin Cycle)

18. Light Dependent Reactions • Split water, produce oxygen gas as waste, & convert ADP & NADP+ into ATP & NADPH

19. Light Dependent Reactions

20. Light Dependent Reactions • Light hits Photosystem II in the thylakoid membranes. Two electrons are excited & these excited electrons are passed onto the Electron Transport Chain. • To replace the lost electrons, the thylakoid membrane obtains low-energy electrons by splitting water: 2H2O  4H+ + O2 + 2 electrons • The O2 is released as waste. • The Hydrogen ions (4H+) are released inside the thylakoid membrane.

21. Light Dependent Reactions

22. Light Dependent Reactions 2. Electron Transport Chain (ETC) • Electrons are passed from Photosystem II to Photosystem I from 1 electron carrier to the next until they reach Photosystem I. • Energy from the electrons is used by the electron carriers in the ETC to force H+ ions from the stroma into the inner thylakoid space. Build up of H+ will be used to drive ATP Synthase!

23. Light Dependent Reactions

24. Light Dependent Reactions 3. Light hits Photosystem I. • Pigments in Photosystem I use energy from light to energize two electrons, making them high-energy. • They are passed to NADP+ Reductase, which catalyzes the reaction of NADP+ to combine with the high-energy electrons & hydrogen ions (H+) to become NADPH. NADP+ + 2 electrons + H+ NADPH

25. Light Dependent Reactions

26. Light Dependent Reactions 4. Hydrogen Ion Movement • The inside of the thylakoid membrane fills up with positively charged hydrogen ions (H+) as electrons are passed from Photosystem II to Photosystem I. • ATP Synthesis • The thylakoid membrane contains a protein called ATP Synthase that spans the membrane & allows H+ ions to pass through it. • As H+ ions pass through ATP Synthase, the protein rotates & binds ADP & a phosphate group to produce ATP.

27. Light Dependent Reactions

28. Light Independent ReactionsAKA The Calvin Cycle • During the Calvin Cycle, plants use ATP & NADPH (made in the Light Dependent Reactions) to produce high-energy sugars for long term storage. • Does NOT require light!

29. The Calvin Cycle • CO2 enters the cycle. • Six carbon dioxide molecules enter & combine with six 5-carbon molecules. • Result: twelve 3-carbon molecules

30. The Calvin Cycle 2. Energy Input • The twelve 3-carbon molecules are converted into high-energy forms using ATP & NADPH. • During this process, 12 ATP  12 ADP • During this process, 12 NADPH  NADP+

31. The Calvin Cycle 3. 6-carbon sugar produced from two 3-carbon molecules 4. 5-carbon molecules regenerated • 10 remaining 3-carbon molecules converted into six 5-carbon molecules • This requires 6 ATP  6 ADP • These 5-carbon molecules can be reused in step 1 of the Calvin Cycle.

33. Photosynthesis includes Light- dependent reactions Calvin cycle takes place in uses use take place in Energy from sunlight Thylakoid membranes ATP Stroma NADPH to produce to produce of High-energy sugars ATP NADPH O2 Chloroplasts

34. Photosynthesis is important for almost all life on Earth because it — A produces oxygen B uses simple elements C is responsible for most decay D releases usable forms of nitrogen

35. A B • What is this picture showing? • What is letter A? __________ • What is letter B? __________ chloroplast stroma thylakoid

36. The diagram represents plant photosynthetic activities taking place in a “food factory.” CO2 What gas is represented by letter A? _______ What is represented by letter B? __________ C6H12O6

37. Light Dependent or Calvin Cycle? Calvin Cycle • Occurs in the stroma • Needs CO2 • Produces ATP and NADPH • Occurs in the thylakoid membranes • Needs sunlight • Can occur in the dark • Uses ATP and NADPH • Produces a 6-Carbon Sugar Calvin Cycle Light Dependent Light Dependent Light Dependent Calvin Cycle Calvin Cycle Calvin Cycle

38. How does exercise affect your body’s production of CO2? • Materials: • Erlenmeyer Flask • Bromothymol Blue (indicator – turns greenish yellow in the presence of acids) • Straws • Water *Hint: CO2 & water form an acid when put together!*