KEY CONCEPT All cells need chemical energy.

1. KEY CONCEPT All cells need chemical energy.

2. Starch molecule Glucose molecule The chemical energy used for most cell processes is carried by ATP. • Molecules in food store chemical energy in their bonds.

3. phosphate removed • ATP transfers energy from the breakdown of food molecules to cell functions. • Energy is released when a phosphate group is removed. • ADP is changed into ATP when a phosphate group is added.

4. adenosine triphosphate tri=3 adenosine diphosphate di=2 Organisms break down carbon-based molecules to produce ATP. • Carbohydrates are the molecules most commonly broken down to make ATP. • not stored in large amounts • up to 36 ATP from one glucose molecule

5. Fats store the most energy. • 80 percent of the energy in your body • about 146 ATP from a triglyceride • Proteins are least likely to be broken down to make ATP. • amino acids not usually needed for energy • about the same amount of energy as a carbohydrate

6. A few types of organisms do not need sunlight and photosynthesis as a source of energy. • Some organisms live in places that never get sunlight. • In chemosynthesis, chemical energy is used to build carbon-based molecules. • similar to photosynthesis • uses chemical energy instead of light energy

7. Questions • What kind of molecule provides the most ATP when it is broken down? • Why do organisms need to digest food?

8. KEY CONCEPTThe overall process of photosynthesis produces sugars that store chemical energy.

9. Photosynthetic organisms are producers. • Producers make their own source of chemical energy. • Plants use photosynthesis and are producers. • Photosynthesis captures energy from sunlight to make sugars.

10. chloroplast leaf cell leaf • Chlorophyll is a molecule that absorbs light energy. • In plants, chlorophyll is found in organelles called chloroplasts.

11. grana (thylakoids) chloroplast stroma Photosynthesis in plants occurs in chloroplasts. • Photosynthesis takes place in two parts of chloroplasts. • grana (thylakoids) • stroma

12. The light-dependent reactions capture energy from sunlight. • take place in thylakoids • water and sunlight are needed • chlorophyll absorbs energy • energy is transferred along thylakoid membrane then to light-independent reactions • oxygen is released

13. The light-independent reactions make sugars. • take place in stroma • needs carbon dioxide from atmosphere • use energy to build a sugar in a cycle of chemical reactions

14. granum (stack of thylakoids) 1 chloroplast sunlight 6H2O 6O2 2 energy thylakoid stroma (fluid outside the thylakoids) 6CO2 1 six-carbon sugar C6H12O6 3 4 • The equation for the overall process is: 6CO2 + 6H2O  C6H12O6 + 6O2

15. Questions • What is the role of chlorophyll in photosynthesis? • What is the overall purpose of photosynthesis? • Describe the overall process of photosynthesis using the equation to determine what information to include.

16. KEY CONCEPT Photosynthesis requires a series of chemical reactions.

17. The first stage of photosynthesis captures and transfers energy. • The light-dependent reactions include groups of molecules called photosystems.

18. 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. 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

20. The light-dependent reactions produce ATP. • hydrogen ions flow through a channel in the thylakoid membrane • ATP synthase attached to the channel makes ATP

21. The second stage of photosynthesis uses energy from the first stage to make sugars. • Light-independent reactions occur in the stroma and use CO2 molecules.

22. A molecule of glucose is formed as it stores some of the energy captured from sunlight. • carbon dioxide molecules enter the Calvin cycle • energy is added and carbon molecules are rearranged • a high-energy three-carbon molecule leaves the cycle

23. A molecule of glucose is formed as it stores some of the energy captured from sunlight. • two three-carbon molecules bond to form a sugar • remaining molecules stay in the cycle

24. Questions • Describe a photosystem • When/where does water and oxygen play into this process • What is the ultimate product of photosystem? • What are the by products?

25. KEY CONCEPT Life in an ecosystem requires a source of energy.

26. Producers provide energy for other organisms in an ecosystem. • Producers get their energy from non-living resources. • Producers are also called autotrophs because they make their own food.

27. Producers provide energy for other organisms in an ecosystem. • Consumers are organisms that get their energy by eating other living or once-living resources. • Consumers are also called heterotrophs because they feed off of different things.

28. carbon dioxide + water + hydrogen sulfide + oxygen sugar + sulfuric acid Almost all producers obtain energy from sunlight. • Photosynthesis in most producers uses sunlight as an energy source. • Chemosynthesis in prokaryote producers uses chemicals as an energy source.

29. Section 2 The Calvin Cycle Chapter 6 Alternative Pathways • The C4 Pathway • Some plants that evolved in hot, dry climates fix carbon through the C4 pathway. These plants have their stomata partially closed during the hottest part of the day. • Certain cells in these plants have an enzyme that can fix CO2 into four-carbon compounds even when the CO2 level is low and the O2 level is high. These compounds are then transported to other cells, where the Calvin cycle ensues.

30. Section 2 The Calvin Cycle Chapter 6 Alternative Pathways, continued • The CAM Pathway • Some other plants that evolved in hot, dry climates fix carbon through the CAM pathway. These plants carry out carbon fixation at night and the Calvin cycle during the day to minimize water loss.

31. Section 2 The Calvin Cycle Chapter 6 Factors That Affect Photosynthesis • Light Intensity • The rate of photosynthesis increases as light intensity increases, because more electrons are excited in both photosystems. • However, at some point all of the available electrons are excited, and the maximum rate of photosynthesis is reached. The rate then stays level regardless of further increases in light intensity.

32. Section 2 The Calvin Cycle Chapter 6 Factors That Affect Photosynthesis, continued • Carbon Dioxide Levels • As with increasing light intensity, increasing levels of carbon dioxide also stimulate photosynthesis until the rate levels off.

33. Section 2 The Calvin Cycle Chapter 6 Factors That Affect Photosynthesis, continued • Temperature • As temperature increases, the rate of photosynthesis increases to a maximum and then decreases with further rises in temperature. • The rate peaks at a certain temperature, at which many of the enzymes that catalyze the reactions become ineffective. Also, the stomata begin to close, limiting water loss and entry of carbon dioxide.