1. Pathways that Harvest and Store Chemical Energy6
Pathways that Harvest and Store Chemical Energy

2. Five principles governing metabolic pathways:
Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism
Five principles governing metabolic pathways:
1. Chemical transformations occur in a series of intermediate reactions that form a metabolic pathway.
2. Each reaction is catalyzed by a specific enzyme.
3. Most metabolic pathways are similar in all organisms.

3. Concept 6.1 ATP, Reduced Coenzymes, and Chemiosmosis Play Important Roles in Biological Energy Metabolism
4. In eukaryotes, many metabolic pathways occur inside specific organelles.
5. Each metabolic pathway is controlled by enzymes that can be inhibited or activated.

4. They are the producers for all food chains on Earth!
What are the energy processing strategies that autotrophs use to obtain free energy?
Use energy from the environment to convert inorganic molecules into organic compounds where free energy is stored
They are the producers for all food chains on Earth!
Examples: photosynthetic and chemosynthetic
LINK Concept 3.4 Review the discussion of enzyme regulation

5. How do photosynthetic organisms obtain free energy?
Use visible light energy to convert water and CO2 in to organic compounds (sugar precursor molecules) and oxygen gas (waste)
Ex: ALL plants, phytoplankton (cyanobacteria and protists)

6. Are plants the only photosynthetic organisms?
NO!
Most of the oxygen in the atmosphere was produced by cyanobacteria and photosynthetic protists (phytoplankton)

7. Photosynthesis Reaction

8. Water and CO2 are both required for photosynthesis
Water and CO2 are both required for photosynthesis...How do they get to the sites of photosynthesis?

9. Photosynthesis is a two part process
Light Reactions (light dependent)
Carbon Fixation (Calvin Cycle; Dark reaction; Light Independent)

10. Photosynthesis is described as an endergonic redox process
Why endergonic?
What substance is oxidized?
To what is it oxidized?
What substance is reduced?
To what is it reduced?

11. What is light?
Light is energy!
Photons of specific wavelengths of light are used in the light reactions

12. What are the major photosynthetic pigments
What are the major photosynthetic pigments? Is this the only photosynthetic pigment?
In plants, two chlorophylls absorb light energy chlorophyll a and chlorophyll b.
PROTEINS!
Accessory pigments—additional pigments that can absorb other wavelengths of light energy

13. Why are plants green?
Chloroplasts cannot absorb all wavelengths of light equally and they reflect green

14. The light reactions occur in the thylakoid membranes
The Chloroplast
Chloroplasts are adapted to separate the light reactions from carbon fixation
The light reactions occur in the thylakoid membranes
Carbon fixation takes place in the stroma

15. Figure 6.15 An Overview of Photosynthesis

16. How do photosynthetic prokaryotic organisms carry out photosynthesis?
Internal folding of the plasma membrane and presence of chlorophyll provides a specialized site for photosynthesis to occur

17. Overview of the Light Reactions
Occurs: in photosystems (membrane proteins and pigment proteins) in the thylakoid membranes of chloroplasts
Uses: Water, light, NADP+, and ADP
Produces: O2 (waste), NADPH, and ATP

18. Figure 6.18 The Molecular Structure of Chlorophyll (Part 1)

19. Figure 6.18 The Molecular Structure of Chlorophyll (Part 2)

20. What happens when chlorophyll absorbs light energy?79

21. What happens when chlorophyll absorbs light energy?
Chlorophyll molecules in photosystems produce high energy electrons when exposed to photons
Excited Electrons move through electron transport chains between photosystems
This releases free energy used to move protons across the thylakoid membrane

22. Non-cyclic electron flow

23. Figure 6.19 Noncyclic Electron Transport Uses Two Photosystems

24. 7.3 SCIENTIFIC DISCOVERY: Scientists traced the process of photosynthesis using isotopes
Experiment 1: 6 CO2  12 H2O → C6H12O6  6 H2O  6 O2
Experiment 2: 6 CO2  12 H2O → C6H12O6  6 H2O  6 O2
Student Misconceptions and Concerns
Students may not connect the growth in plant mass to the fixation of carbon during the Calvin cycle. It can be difficult for many students to appreciate that molecules in air can contribute significantly to the mass of plants.
Teaching Tips
Many students do not realize that glucose is not the direct product of photosynthesis. Although glucose is often shown as a final product of photosynthesis, a three-carbon sugar is directly produced (G3P, as the authors note later in Module 7.10). A plant can use G3P to make many types of organic molecules, including glucose.
© 2012 Pearson Education, Inc. 24

25. What is the role of water in the light reactions?
Water is decomposed at PSII to supply chlorophyll with replacement electrons
This produces waste O2

26. How is ATP produced in non-cyclic electron flow?
Chemiosmosis!
The high concentration of H+ in the thylakoid space passively diffuse through ATP synthase enzyme

27. Electrons in the ETC are used to reduce NADP+ to NADPH
How is NADPH produced? Why is it considered a “final electron acceptor”
Electrons in the ETC are used to reduce NADP+ to NADPH
NADPH “accepts” the electrons at the end of the ETC

28. Figure 6.20 Cyclic Electron Transport Traps Light Energy as ATP

29. Summary of the Light Dependent Reactions:
Location?
Reactants (4)?
Products (4)?
**The ATP and NADPH produced are needed for the light independent reactions to take place**
ANIMATED TUTORIAL 6.5 Tracing the Pathway of CO2

30. Overview of the Calvin Cycle
Occurs: in the stroma of the chloroplast
Uses: CO2, NADPH, and ATP
Produces: Organic Molecules (G3P), NADP+, and ADP

31. How can we describe the process of carbon fixation?
The ATP and NADPH produced during the L.D. reactions will be used to drive the incorporation of CO2 in to an organic sugar building block called G3P

32. Figure 6.22 RuBP Is the Carbon Dioxide Acceptor

33. What is the first step of the Calvin Cycle
What is the first step of the Calvin Cycle? What is the name of the enzyme that catalyzes this reaction? This is carbon fixation.
Carbon dioxide is incorporated into the Calvin Cycle by the enzyme RuBisCo. This reaction turns a 5-Carbon RuBP molecule into two 3-Carbon PGA molecules

34. How are ATP and NADPH used in the Calvin Cycle?
The energy in ATP and the electrons in NADPH are used to reduce the PGA molecules into 3- Carbon G3P molecules. A total of 12 G3P molecules are produced

35. 10 of the 12 molecules produced are used to regenerate RuBP…Why?
G3P is the 3-Carbon organic compound produced during the calvin cycle. What are the possible fates of the G3P molecules produced?
10 of the 12 molecules produced are used to regenerate RuBP…Why?
2 G3P molecules exit the stroma and can be combined to…
Make sugars and be used in C.R.
Excess glucose stored as starch
Make lipids, amino acids, or nucleotides

36. Why is photosynthesis the most important biological reaction on Earth?
The C—H bonds generated by the Calvin cycle provide almost all the energy for life on Earth.
Autotrophs and Heterotrophs rely on this chemical energy to support their own growth and reproduction!
LINK Concept 45.3 The roles of autotrophs and heterotrophs in ecosystems are described

37. Photosynthesis Determines Global Productivity

38. Summary of the Calvin Cycle:
Location:
Reactants:
Products:
ANIMATED TUTORIAL 6.5 Tracing the Pathway of CO2

39. Figure 6.21 The Calvin Cycle