1. UNIT IV – CELLULAR ENERGY Hillis ~ Ch 2,6 Big Campbell ~ Ch 8,9,10 Baby Campbell ~ Ch 5,6,7 Dual Campbell Ch 6,7,8

2. I. THE WORKING CELL Energy  Kinetic Energy  Potential Energy  Chemical Energy

3. I. THE WORKING CELL, cont Thermodynamics  First Law of Thermodynamics  Total amount of energy in universe is constant  Second Law of Thermodynamics  Energy is lost to the environment as heat; that is, some energy becomes unusable

4. I. THE WORKING CELL, cont Metabolism   Two types of reactions    Exergonic    Endergonic

5. I. THE WORKING CELL, cont  Gibbs Free Energy (ΔG)

6. I. THE WORKING CELL, cont  ΔG and Enzyme Catalysis

7. I. THE WORKING CELL, cont  Energy Coupling  Energy released in exergonic rxn is used to drive endergonic rxn.

8. II. ATP Adenosine Triphosphate  Nucleotide that stores & provides usable energy to the cell  Structure of ATP   ATP contains potential energy, especially between 2 nd and 3 rd phosphate groups.  P – P bond is unstable  Easily broken by

9. II. ATP, cont ATP → ADP + P i   Coupled with endergonic rxn – specifically, by transferring phosphate group from ATP to another molecule.

10. II. ATP, cont ADP + P i → ATP   Mechanisms for “making” ATP  Substrate-level Phosphorylation  Oxidative Phosphorylation  Photophosphorylation

11. II. ATP, cont Substrate-Level Phosphorylation vs. Oxidative/Photo Phosphorylation

12. III. ♪ ♫ THE CYCLE OF LIFE ♪ ♫ Photosynthesis o Cellular Respiration o

13. IV. ENERGY IN THE CELL Oxidation-Reduction Reactions o Energy yield in catabolism comes from transfer of electrons o Movement of electrons releases chemical energy of molecule  Released energy used to generate ATP from ADP and P i o Known as redox reaction  Oxidation   Reduction 

14. IV. ENERGY IN THE CELL, cont Oxidation-Reduction Reactions, cont  Electron movement in molecules often traced by changes in H atom distribution

15. IV. ENERGY IN THE CELL, cont Importance of Electron Carriers o Energy contained in molecules (for example, glucose) must be released in a series of steps  Electrons released as hydrogen atoms with corresponding proton  Hydrogen atoms are passed to an electron carrier o Electron carriers are coenzymes o “Carry” 2 electrons in the form of H-atoms o Allow for maximum energy transfer, minimum energy loss

16. IV. ENERGY IN THE CELL, cont Electron Carriers  NAD +  Nicotinamide adenine dinucleotide  Electron acceptor in cellular respiration  Reduced to  FAD  Flavin adenine dinucleotide  Electron acceptor in Krebs Cycle  Reduced to  NADP +  Nicotinamide adenine dinucleotide phosphate  Electron acceptor in light reaction of photosynthesis  Reduced to

17. V. PHOTOSYNTHESIS – AN OVERVIEW Photosynthesis – Process of capturing ___________ energy and converting it to ________________ energy Plants are __________________; also known as _____________ Redox Reaction

18. V. PHOTOSYNTHESIS – AN OVERVIEW, cont Water Movement  Root Structure  Ψ  Transpiration

19. V. PHOTOSYNTHESIS – AN OVERVIEW, cont Leaf Structure  Epidermis  Cuticle  Stomata & Guard Cells  Mesophyll Chloroplast Structure  Thylakoids –  Site of Light Reaction  First step in photosynthesis  Granum  Stroma  Site of Calvin Cycle  Second step in photosynthesis

20. VI. LIGHT REACTION OF PHOTOSYNTHESIS Occurs in thylakoid membranes Converts light energy to chemical energy Light energy o Visible light is a small portion of the electromagnetic spectrum. o Light absorbed by chlorophyll and other photosynthetic pigments to power reactions is not seen. Light not utilized by plant is reflected & seen by human eye. o Light energy measured in photons.

21. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont Photosynthetic pigments  Chlorophyll a – absorbs mainly blue-violet and red light  Chlorophyll b – absorbs mainly blue and orange light  Carotenoids – other accessory pigments; expand spectrum of light energy that can be used for photosynthesis

22. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont A photon of light energy is absorbed by pigment molecule in Photosystem II. Energy is passes from one molecule to another until it reaches P680 - pair of chlorophyll a molecules. Electron in each is excited to higher energy state – transferred to primary electron acceptor. Water is split to replace electron lost by P680. O 2 is released. H + ions remain.

23. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont Excited electron moves from primary electron acceptor to Photosystem I via electron transport chain. As electron “falls”, energy is released. Used to synthesize ATP through chemiosmosis. Known as photophosphorylation

24. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont Light energy is transferred via light-harvesting complexes to P700 in Photosystem I. Excited electron is captured by primary electron acceptor. P700’s electron is replaced by electron transport chain on Photosystem II. Electron from P700 moves through a short electron transport chain, reducing NADP + to NADPH.

25. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont Linear Electron Flow

26. VI. LIGHT REACTION OF PHOTOSYNTHESIS, cont Cyclic Electron Flow oAlternative pathway seen in some bacteria, plants oMay be photoprotective in plants oOnly utilizes Photosystem I oNo NADPH production oNo O 2 release oDoes generate ATP

27. VII. CALVIN CYCLE OF PHOTOSYNTHESIS Also known as Dark Reaction, Light- Independent Rxn Occurs in stroma of chloroplasts “Synthesis” part of photosynthesis; utilizes ATP, NADPH generated in Light Reaction + CO 2 to produce organic molecules Anabolic; endergonic Requires enzyme Rubisco Three basic steps  Carbon Fixation  Reduction  Regeneration of RuBP

28. VII. CALVIN CYCLE OF PHOTOSYNTHESIS, cont

29. VII. CALVIN CYCLE OF PHOTOSYNTHESIS, cont Sugar Transport

30. VIII. PHOTORESPIRATION Counterproductive pathway that produces 2-C molecule, which is then released as CO 2 Due to oxygen competing for active site of Rubisco Consumes ATP; decrease carbohydrate yield

31. VIII. PHOTORESPIRATION, cont Plant Adaptations  C4 Plants

32. VIII. PHOTORESPIRATION, cont Plant Adaptations, cont  CAM Plants

33. IX. CELLULAR RESPIRATION – AN OVERVIEW Process used by cells to convert chemical energy in glucose (and other molecules) to ATP Primarily takes place in mitochondria of eukaryotic cells Overall Reaction

34. IX. CELLULAR RESPIRATION OVERVIEW, cont 1)Glycolysis  “Sugar-breaking”  Initial breakdown of glucose to intermediate, some ATP 2)Pyruvate Oxidation  Occurs in mitochondria 3)Krebs Cycle  Completes oxidation of glucose to CO 2  Produces ATP, but more importantly provides high-energy electrons for etc 4)Electron Transport Chain  Oxidative Phosphorylation  Highest ATP yield; uses energy released from downhill flow of electrons to generate ATP

35. X. GLYCOLYSIS Occurs in cytosol of cell Does not require oxygen First part of pathway is energy investment phase Second part of pathway is energy pay-off phase Energy Investment Phase

36. X. GLYCOLYSIS, cont Energy Pay-Off Phase

37. X. GLYCOLYSIS, cont Summary of Glycolysis

38. XI. OXIDATIVE RESPIRATION Pyruvate Oxidation o Oxygen must be available o Takes place in mitochondrial matrix prior to Citric Acid Cycle …  Carboxyl group of pyruvate is removed, given off as CO 2  Remaining 2-C molecule is oxidized to acetate → NAD + reduced to NADH + H +  Acetate binds to molecule known as Coenzyme A to form acetyl CoA

39. XI. OXIDATIVE RESPIRATION, cont Citric Acid Cycle ( Krebs cycle, tricarboxylic acid cycle, TCA cycle) o 2-C molecule goes through a series of redox rxns. o Occurs in mitochondrial matrix o Produces NADH, FADH 2, ATP, and CO 2. o CoA is not actually a part of the reaction... it is recycled... remember, it is an enzyme!

40. XI. OXIDATIVE RESPIRATION, cont Oxidative Phosphorylation o Traditionally called Electron Transport o Occurs in inner mitochondrial membrane  Membrane organized into cristae to increase surface area o Two components to Oxidative Phosphorylation  Electron Transport Chain  Chemiosmosis

41. XI. OXIDATIVE RESPIRATION, cont Oxidative Phosphorylation o Electron Transport Chain  Collection of molecules, each more electronegative than the one before it  Molecules are reduced, then oxidized as electrons are passed down the chain  Oxygen is ultimate electron acceptor  Purpose is to establish H + gradient on two sides of inner mitochondrial membrane  Energy from “falling electrons” used to pump H + from matrix into intermembrane space

42. XI. OXIDATIVE RESPIRATION, cont Oxidative Phosphorylation o Chemiosmosis  Enzyme complexes known as ATP synthases located in inner mitochondrial membrane  H + electrochemical gradient provides energy  Known as proton motive force  Movement of H + ions through membrane rotates enzyme complex  Rotation exposes active sites in complex  ATP is produced from ADP and P i

43. XI. OXIDATIVE RESPIRATION, cont A summary of oxidative phosphorylation...

44. XI. OXIDATIVE RESPIRATION, cont

45. XII. CELLULAR RESPIRATION – A SUMMARY Each NADH shuttled through ETC results in approximately _________ ATP Each FADH 2 shuttled through ETC results in approximately _________ ATP. Total ATP Gain in Cellular Respiration = ____ (glycolysis) + ____ (citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP / glucose

46. XII. CELLULAR RESPIRATION – A SUMMARY, cont

48. XIII. CATABOLISM OF OTHER FOOD MOLECULES

49. XIV. METABOLIC POISONS Blockage of Electron Transport Chain Inhibition of ATP Synthase “Uncouplers” o Prevent creation of H + ion gradients due to leakiness of mitochondrial membrane

50. XV. FERMENTATION Anaerobic pathway Occurs in cytosol Purpose Glycolysis

51. XV. FERMENTATION, cont