Lesson Overview

1. Lesson Overview 8.1 Energy and Life

2. Chemical Energy and ATP • Adenosine Triphosphate (ATP) – VERY IMPORTANT ENERGY MOLECULE • ATP consists of • 1. adenine • 2. 5-carbon sugar called ribose • 3. three phosphate groups

3. Using Biochemical Energy • ATP is not good for storing energy or for long term use • cells keep small amount of ATP for use • Cells can regenerate ATP by using the energy in foods like glucose

4. Heterotrophs and Autotrophs • Heterotrophs - obtain food by consuming other living things; various types (herbivores, carnivores, etc) • Autotrophs - organisms that make their own food; generally use sunlight to make food (photosynthesis)

5. Lesson Overview 8.2 Photosynthesis: An Overview http://www.wwnorton.com/college/biology/discoverbio3/core/content/index/animations.asp

6. Light • Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum

7. Pigments • Plants gather the sun’s energy with light-absorbing molecules called pigments • chlorophyll– main pigment in plants

8. Pigments • Two types of chlorophyll found in plants: • chlorophyll a and chlorophyll b • Another pigment found in plants • carotene

9. Chloroplasts • Photosynthesis takes place inside chloroplasts • Chloroplast structure includes: • double membrane • thylakoids (contain pigments) • grana (stacks of thylakoids) • stroma (fluid)

10. Energy Collection • When chlorophyll absorbs light, the energy is transferred to electrons

11. High-Energy Electrons • Energy in electrons must be transferred to other molecules to make food for the plant • Electron carriers are used to transfer the energy to another molecule

12. High-Energy Electrons • NADP+ - a carrier molecule used in photosynthesis • NADPH - carry the high-energy electrons to chemical reactions elsewhere in the cell

13. An Overview of Photosynthesis • Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high-energy sugars and oxygen.

14. PHOTOSYNTHESIS • Photosynthesis involves two sets of reactions: • 1. light-dependent reactions • 2. light-independent reactions

15. Light-Dependent Reactions • The light-dependent reactions use sunlight & water to produce ATP , NADPH(energy molecules), and oxygen • Take place within the thylakoid membranes

16. Light-Independent Reactions • During light-independent reactions, ATP, NADPH, and carbon dioxideare used to produce high-energy sugars • Light-independent reactions take place in the stroma (fluid)

17. Lesson Overview 8.3 The Process of Photosynthesis

18. The Light-Dependent Reactions: Generating ATP and NADPH • Photosystems (clusters of chlorophyll/proteins) absorb sunlight and generate high-energy electrons that are then passed to a series of electron carriers embedded in the thylakoid membrane

19. Photosystem II • Light energy is absorbed in the pigments within photosystem II, “exciting” electrons • These electrons are passed to the electron transport chain (ETC)

20. Photosystem II • Enzymes of the inner surface of the thylakoid break up water molecules into 2 electrons, 2 H+ ions, and 1 oxygen atom: • 2 electrons – go to PS II to replace other electrons • Oxygen – released into atmosphere • H+- create gradient to create ATP • ***WATER IS A PRETTY IMPORTANT PART OF THE EQUATION!!!

21. Electron Transport Chain • Energy from the electrons used to pump H+ from stroma into thylakoid space • Electrons wind up at PS I (chlorophyll/proteins); need to be “recharged/re-energized” by sunlight

22. Photosystem I • At end of ETC, electrons combine with H+ and NADP+ to make NADPH

23. Hydrogen Ion Movement and ATP Formation • H+ ions accumulate within the thylakoid space during process, creating a gradient • This gradient provides the energy to make ATP (using ATP synthase to pump H+) - chemiosmosis

24. Summary of Light-Dependent Reactions • The light-dependent reactions produce oxygen, ATP, and NADPH • ATP and NADPH will be used in LIGHT-INDEPENDENT REACTIONS to make sugar

25. The Light-Independent Reactions: Producing Sugars • Light-independent reactions, also known as Calvin cycle, require CO2, ATP, and NADPH to make sugar • Takes place in stroma

26. Carbon Dioxide Enters the Cycle • CO2 molecules enter the Calvin cycle from the atmosphere • An enzyme (rubisco) in the stroma combines carbon dioxide molecules with 5-carbon compounds = CARBON FIXATION

27. Carbon Dioxide Enters the Cycle • The 3-carbon compounds use energy from ATP and NADPH to change throughout the cycle

28. Sugar Production • 2 3-carbon molecules leave the cycle to become food for the plant • The rest of the carbon compounds are converted back into the beginning 5 carbon compounds to start cycle again

29. Factors Affecting Photosynthesis • Among the most important factors that affect photosynthesis are • temperature, light intensity, and the availability of water. • Average temp best (due to enzyme activity) • high light intensity (up to a point) • lack of water will slow or prevent photosynthesis

30. Photosynthesis Under Extreme Conditions • Most plants under bright, hot conditions close the small openings in their leaves that normally admit carbon dioxide (to conserve water) • Carbon dioxide falls to very low levels, slowing down or even stopping photosynthesis. • C4 and CAM plants have biochemical adaptations that minimize water loss while still allowing photosynthesis to take place in intense sunlight • C4 plants – corn, sugarcane • CAM plants – pineapple, cacti