Energy Conversion in Cell: ATP, Photosynthesis, and Cellular Respiration

1. Chapter 10 Cell Energy- ATP Photosynthesis and Cellular Respiration

2. Cool “Fires” Attract Mates and Meals • Fireflies use light, instead of chemical signals, to send signals to potential mates • Females can also use light flashes to attract males of other firefly species — as meals, not mates

3. The light comes from a set of chemical reactions, the luciferin-luciferase system • Fireflies make light energy from chemical energy • Life is dependent on energy conversions

4. ENERGY AND THE CELL • Living cells are compartmentalized by membranes • Membranes are sites where chemical reactions can occur in an orderly manner • Living cells process energy by means of enzyme-controlled chemical reactions

5. Energy is the capacity to perform work • Energy is defined as the capacity to do work • All organisms require energy to stay alive • Energy makes change possible

6. Chemical reactions either store or release energy • Cells carry out thousands of chemical reactions • The sum of these reactions constitutes cellular metabolism

7. ATP shuttles chemical energy within the cell • In cellular respiration, some energy is stored in ATP molecules • ATP powers nearly all forms of cellular work • ATP molecules are the key to energy coupling

8. When the bond joining a phosphate group to the rest of an ATP molecule is broken by hydrolysis, the reaction supplies energy for cellular work Adenine Phosphategroups Hydrolysis Energy Ribose Adenosine triphosphate Adenosine diphosphate(ADP)

9. How ATP powers cellular work Reactants Products Potential energy of molecules Work Protein

10. The ATP cycle Hydrolysis Dehydration synthesis Energy from exergonic reactions Energy for endergonic reactions

11. Life in the Sun • Light is central to the life of a plant • Photosynthesis is the most important chemical process on Earth • It provides food for virtually all organisms • Plant cells convert light into chemical signals that affect a plant’s life cycle

12. Light can influence the architecture of a plant • Plants that get adequate light are often bushy, with deep green leaves • Without enough light, plants become tall and spindly with small pale leaves • Too much sunlight can damage a plant • Chloroplasts and carotenoids help to prevent such damage

13. AN OVERVIEW OF PHOTOSYNTHESIS • Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbondioxide Water Glucose Oxygengas PHOTOSYNTHESIS

14. Autotrophs are the producers of the biosphere • Plants, some protists, and some bacteria are photosynthetic autotrophs • They are the ultimate producers of food consumed by virtually all organisms

15. On land, plants such as oak trees and cacti are the predominant producers

16. In aquatic environments, algae and photosynthetic bacteria are the main food producers

17. Photosynthesis occurs in chloroplasts • In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts • A chloroplast contains: • stroma, a fluid • grana, stacks of thylakoids • The thylakoids contain chlorophyll • Chlorophyll is the green pigment that captures light for photosynthesis

18. The location and structure of chloroplasts Chloroplast LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll Intermembrane space CHLOROPLAST Outer membrane Granum Innermembrane Grana Stroma Thylakoidcompartment Stroma Thylakoid

19. Plants produce O2 gas by splitting water • The O2 liberated by photosynthesis is made from the oxygen in water

20. Overview: Photosynthesis occurs in two stages linked by ATP and NADPH • The complete process of photosynthesis consists of two linked sets of reactions: • the light reactions and the Calvin cycle • The light reactions convert light energy to chemical energy and produce O2 • The Calvin cycle assembles sugar molecules from CO2 using the energy-carrying products of the light reactions

21. An overview of photosynthesis H2O CO2 Chloroplast Light NADP+ ADP+ P LIGHTREACTIONS(in grana) CALVINCYCLE(in stroma) ATP Electrons NADPH O2 Sugar

22. THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY • Certain wavelengths of visible light drive the light reactions of photosynthesis Gammarays Micro-waves Radio waves X-rays UV Infrared Visible light Wavelength (nm)

23. Reflectedlight Light Chloroplast Absorbedlight Transmittedlight

24. Photosystems capture solar power • Each of the many light-harvesting photosystems consists of: • an “antenna” of chlorophyll and other pigment molecules that absorb light • a primary electron acceptor that receives excited electrons from the reaction-center chlorophyll

25. Primaryelectron acceptor PHOTOSYSTEM Photon Reaction center Pigmentmoleculesof antenna

26. Fluorescence of isolated chlorophyll in solution Heat Photon(fluorescence) Photon Chlorophyllmolecule

27. Excitation of chlorophyll in a chloroplast Primaryelectron acceptor Othercompounds Photon Chlorophyllmolecule

28. In the light reactions, electron transport chains generate ATP, NADPH, and O2 • Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons • The excited electrons are passed from the primary electron acceptor to electron transport chains • Their energy ends up in ATP and NADPH

29. Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product Primaryelectron acceptor Electron transport Primaryelectron acceptor Electron transport chain Photons Energy forsynthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis

30. The production of ATP by chemiosmosis in photosynthesis Thylakoidcompartment(high H+) Light Light Thylakoidmembrane Antennamolecules Stroma(low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE

31. THE CALVIN CYCLE: CONVERTING CO2 TO SUGARS ATP and NADPH power sugar synthesis in the Calvin cycle • The Calvin cycle occurs in the chloroplast’s stroma • This is where carbon fixation takes place and sugar is manufactured CALVINCYCLE OUTPUT:

32. Details of the Calvin cycle INPUT: 3 In a reaction catalyzed by rubisco, 3 molecules of CO2 are fixed. CO2 Step Carbon fixation. 1 1 3 P P 6 P RuBP 3-PGA 6 ATP 3 ADP Step Energy consumption and redox. 2 6 ADP + P CALVINCYCLE 3 ATP 2 6 4 NADPH 6 NADP+ Step Release of one molecule of G3P. 3 5 P 6 P G3P G3P 3 Step Regeneration of RuBP. 4 Glucoseand other compounds OUTPUT: 1 P G3P

33. PHOTOSYNTHESIS REVIEWED AND EXTENDED Review: Photosynthesis uses light energy to make food molecules Chloroplast Light • A summary of the chemical processes of photo-synthesis Photosystem IIElectron transport chains Photosystem I CALVIN CYCLE Stroma Electrons Cellular respiration Cellulose Starch Other organic compounds LIGHT REACTIONS CALVIN CYCLE

34. Many plants make more sugar than they need • The excess is stored in roots, tuber, and fruits • These are a major source of food for animals

35. STAGES OF CELLULAR RESPIRATION AND FERMENTATION Overview: Respiration occurs in three main stages • Cellular respiration oxidizes sugar and produces ATP in three main stages • Glycolysis occurs in the cytoplasm • The Krebs cycle and the electron transport chain occur in the mitochondria

36. An overview of cellular respiration High-energy electrons carried by NADH GLYCOLYSIS ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS KREBSCYCLE Glucose Pyruvicacid Cytoplasmicfluid Mitochondrion

37. Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid Glucose Pyruvicacid

38. The Krebs cycle completes the oxidation of organic fuel Acetyl CoA • The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group 2 KREBSCYCLE CO2

39. 2 carbons enter cycle Oxaloaceticacid 1 Citric acid CO2 leaves cycle 5 KREBSCYCLE 2 Malicacid 4 Alpha-ketoglutaric acid 3 CO2 leaves cycle Succinicacid Step Acetyl CoA stokesthe furnace Steps and NADH, ATP, and CO2 are generatedduring redox reactions. Steps and Redox reactions generate FADH2and NADH. 1 2 3 4 5

40. Chemiosmosis in the mitochondrion Proteincomplex Intermembranespace Electroncarrier Innermitochondrialmembrane Electronflow Mitochondrialmatrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE

41. Connection:Certain Poisons can interrupt the “chain” Rotenone Oligomycin Cyanide,carbon monoxide ELECTRON TRANSPORT CHAIN ATP SYNTHASE

42. For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules Cytoplasmic fluid Mitochondrion Electron shuttleacrossmembranes KREBSCYCLE GLYCOLYSIS 2AcetylCoA KREBSCYCLE ELECTRONTRANSPORT CHAINAND CHEMIOSMOSIS 2Pyruvicacid Glucose by substrate-levelphosphorylation used for shuttling electronsfrom NADH made in glycolysis by substrate-levelphosphorylation by chemiosmoticphosphorylation Maximum per glucose:

43. Fermentation is an anaerobic alternative to aerobic respiration • Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP • But a cell must have a way of replenishing NAD+

44. In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol • This recycles NAD+ to keep glycolysis working released GLYCOLYSIS 2 Pyruvicacid 2 Ethanol Glucose

45. In lactic acid fermentation, pyruvic acid is converted to lactic acid • As in alcoholic fermentation, NAD+ is recycled • Lactic acid fermentation is used to make cheese and yogurt GLYCOLYSIS 2 Pyruvicacid 2 Lactic acid Glucose

46. Food molecules provide raw materials for biosynthesis • In addition to energy, cells need raw materials for growth and repair • Some are obtained directly from food • Others are made from intermediates in glycolysis and the Krebs cycle • Biosynthesis consumes ATP

47. Biosynthesis of macromolecules from intermediates in cellular respiration ATP needed todrive biosynthesis GLUCOSE SYNTHESIS KREBSCYCLE AcetylCoA Pyruvicacid G3P Glucose Aminogroups Amino acids Fatty acids Glycerol Sugars Proteins Fats Polyscaccharides Cells, tissues, organisms

48. The fuel for respiration ultimately comes from photosynthesis • All organisms have the ability to harvest energy from organic molecules • Plants, but not animals, can also make these molecules from inorganic sources by the process of photosynthesis