8–1 Energy and Life A. Autotrophs and Heterotrophs B. Chemical Energy and ATP 1. Storing Energy

1. Section Outline Section 8-1 • 8–1 Energy and Life A. Autotrophs and Heterotrophs B. Chemical Energy and ATP 1. Storing Energy 2. Releasing Energy C. Using Biochemical Energy

2. What is energy? • The ability to do work. • Cells require energy for any “work” they do: • Cell reproduction • Manufacturing proteins • Movement of materials between cells • To allow tissues in muscles to move (animals)

3. Autotrophs and Heterotrophs • Autotrophs • Have the ability to generate their own food. • Base of many food chains • Plants, bacteria, etc. • Heterotrophs • Must obtain food from other source • Typically the autotrophs • All organisms must obtain/make food in the form of sugars to ultimately be used to create energy.

4. Section Outline Section 8-2 • 8–2 Photosynthesis: An Overview A. Investigating Photosynthesis 1. Van Helmont’s Experiment 2. Priestley’s Experiment 3. Jan Ingenhousz B. The Photosynthesis Equation C. Light and Pigments

5. Photosynthesis • the process of using light energy to convert CO2 and H2O into high energy glucose

6. Photosynthesis: Reactants and Products Section 8-2 Light Energy Chloroplast CO2 + H2O Sugars + O2

7. Early discoveries • Jan Van Helmont • 1643 – discovered plants take in water • Joseph Priestly • 1771 – plants release O2 • Jan Igenhousz • Plants only produce O2 in the presence of light.

8. The Photosynthesis Equation

10. Light CO2 Sugars O2 Figure 8-7 Photosynthesis: An Overview Section 8-3 Chloroplast Chloroplast NADP+ ADP + P Light- Dependent Reactions Calvin Cycle ATP NADPH

12. Figure 8-5 Chlorophyll Light Absorption Section 8-2 Absorption of Light by Chlorophyll a and Chlorophyll b Chlorophyll b Chlorophyll a V B G Y O R

13. Light Used in Photosynthesis • During Photosynthesis, the chlorophyll pigments can absorb only some wavelengths of the visible light from the electromagnetic spectrum. • Visible light consists of the following colors or wavelengths in order of increasing wavelengths / decreasing energy: • Violet, Indigo, Blue,Green, Yellow, Orange and Red. • The grana of the chloroplasts absorb mainly blue-violet and red-orange lights. • Green light is reflected and transmitted by green plants – hence, they appear green.

14. Light • Photon = a discrete packet of light energy. • The shorter the wavelength, the greater the energy….and vice-versa.

15. Pigments • Chlorophyll– “More like Borophyll”…..Billy Madison • Main pigments absorbing light for photosynthesis • Two types: • Chlorophyll a – light green • Chlorophyll b – dark green • Accessory pigments • Found in much smaller quantities • Xanthophyll - yellow • Carotene -orange

16. Section Outline Section 8-3 • 8–3 The Reactions of Photosynthesis A. Inside a Chloroplast B. Electron Carriers C. Light-Dependent Reactions D. The Calvin Cycle E. Factors Affecting Photosynthesis

17. Inside the chloroplast • Contain thylakoid • Site of light reaction • Stacks are called grana • Space in between is known as stroma • Site of Calvin cycle

19. Electron carriers • NADPH • Electrons are typically carried by molecules, especially when they are energized • Because they are negatively charged they are attracted to positive “things” • Electrons will combine with NADP+ and H+ to form NADPH • Called a reduction reaction (NADP+ is reduced) • NADP+ + H+ +2e- NADPH

20. Light Reaction overview • Light reaction – is dependent on light and occurs only during the day in nature. • It takes place in the thylakoid membrane of the chloroplast. • Light reactions involve • a) Splitting of water to produce oxygen, • b) Energy production (ATP) and • c) Reduction of NADP+ to NADPH.

21. Light reaction….in detail (now the party begins) • Chlorophyll's role • Provide electrons to be “energized” • Specific wavelengths of light strikes chlorophyll and energize electrons to enter into electron transport chain of light reaction. e-

22. Water’s role • Can chlorophyll run out of electrons? • Theoretically, yes. • Water replenishes the supply to chlorophyll so they can donate electrons to the electron transport chain • Water is split into H+ (Hey, that looks familiar!) and O2 (sort of important stuff – wonder where that goes?!?)

23. e- So what happens? • A specific wavelength of light (680 nm) strikes chlorophyll on the thylakoid membrane. • 2. An electron gets “energized” and enters into the electron transport chain. • 3. Electron “hops” from protein to protein “down hill.” • 4. Energy is released, provides energy for: • ADP + P ATP e-

24. So where does the electron go? • Into another chlorophyll “center” that is losing electrons when 700 nm of light hits it. • Those electrons eventually must join up with NADP+ and H+ to form NADPH (also needed by Calvin cycle) • Electron carriers!

25. Untitled Document

26. How is it made? • Concentration gradients are established by “pumping” H+ into the inner thylakoid space (energy comes from the electron “bouncing down hill”) • H+ naturally tend to diffuse out • This is kinetic energy – energy of motion • ATP synthase uses that energy to put ADP together with P to make ATP

27. Figure 8-10 Light-Dependent Reactions Section 8-3 Hydrogen Ion Movement Chloroplast Photosystem II ATP synthase Inner Thylakoid Space Thylakoid Membrane Stroma Electron Transport Chain Photosystem I ATP Formation

29. So what if ATP is made? • What is it used for? • To run the Calvin Cycle! • So does light directly make food for the plant? • No! Makes the fuel to run the reaction that makes food for the plant!

30. Summary • Light hits chlorophyll P680….. • Electrons energized enter electron transport chain • Water split……… • Replenishes lost electrons • Electrons passed “downhill”……… • Releases energy used to “pump” H+ uphill • P700……….. • Catches electron, 700 nm of light hits it and sends electrons on down to be picked up by NADP • NADP….. • Catches electrons, goes to Calvin Cycle • H+……… • “Fall” or diffuse through ATP synthase, provides energy to make ATP

37. Calvin Cycle • Series of reactions that require energy from ATP and electrons from NADPH • Starting reactant: • CO2 • Finished product: • “G3P” – glyceraldehyde 3-phosphate • G3P is then later processed into sugars, starches etc.

38. http://ppdb.tc.cornell.edu/images/calvincycle9kj7.jpg

39. CARBON FIXATION (3) CO2 molecules enter Rubisco attaches the CO2 to RuBP

40. REDUCTION 6 ATP and 6 NADPH used 1 G3P molecule produced

41. Regenerate RuBP Use 3 more ATP

42. “PGA” • Three carbon molecules formed at the beginning of Calvin • “G3P” • Cell converts later to sugars and carbs • “RuBP” • What combines with CO2, to keep Calvin going.

43. Video 5 Video 5 Calvin Cycle • Click the image to play the video segment.

44. Light- dependent reactions Calvin cycle Energy from sunlight Thylakoid membranes ATP Stroma NADPH High-energy sugars ATP NADPH O2 Chloroplasts Concept Map Section 8-3 Photosynthesis includes takes place in uses use take place in to produce to produce of

45. Now where??? • So what happens with this G3P?? • Converted to sugar based molecules like…. • Glucose/fructose…. – maple syrup anyone? • Starch – French fries, cornbread, and pasta • Cellulose – cell wall material – 2 X 4’s, paper, and Raisin BRAN • Depends on the needs of the cell at that instance • Plants generate 200 billion tons of “Carbs” a year globally! • Atkins would be mortified!

46. Factors affecting photosynthesis • Water deficiencies • Supplies chlorophyll with electrons for light reaction • Temperature • Low temperatures minimize enzyme activity • Most reactions in photosynthesis enzyme driven • Light • Amount of daylight • Why deciduous trees drop leaves and go dormant for the winter

47. Alternative methods of photosynthesis • Tropical plants temporarily fix CO2 by alternate method • Corn, sugar cane, grasses • C4 plants (most plants are C3 – remember PGA?) • CO2 fixed forms a 4-carbon molecule instead of PGA, one of the carbons breaks off, saving an extra carbon dioxide for the regular Calvin Cycle • Why do they feel the need to do so? • Generates lots of CO2 inside the leaf for Calvin • Ok???, So what?

48. Leaf anatomy of plants adapted for hot/arid conditions (C4 plants)… O2 C4 pathway C3 pathway Separate CO2 fixation and sugar making into two different cells