1. © 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 6 Cellular Respiration: Obtaining Energy from Food

2. ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE Animals depend on plants to convert solar energy to: –Chemical energy of sugars –Other molecules we consume as food Photosynthesis: –Uses light energy from the sun to power a chemical process that makes organic molecules. © 2010 Pearson Education, Inc.

3. Producers and Consumers Plants and other autotrophs (self-feeders): –Make their own organic matter from inorganic nutrients. Heterotrophs (other-feeders): –Include humans and other animals that cannot make organic molecules from inorganic ones. Autotrophs are producers because ecosystems depend upon them for food. Heterotrophs are consumers because they eat plants or other animals.

4. Figure 6.1 – Producer and Consumer: A parrot (consumer) eats a fruit produced by a plant (producer).

5. Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide and water. –CO 2 is obtained from the air by a plant’s leaves. –H 2 O is obtained from the damp soil by a plant’s roots. Chloroplasts in the cells of leaves: –Use light energy to rearrange the atoms of CO 2 and H 2 O, which produces –Sugars (such as glucose) –Other organic molecules –Oxygen © 2010 Pearson Education, Inc.

6. Plant and animal cells perform cellular respiration, a chemical process that: –Primarily occurs in mitochondria –Harvests energy stored in organic molecules –Uses oxygen –Generates ATP The waste products of cellular respiration are: –CO 2 and H 2 O –Used in photosynthesis

7. © 2010 Pearson Education, Inc. Animals perform only cellular respiration. Plants perform: –Photosynthesis and –Cellular respiration

8. Sunlight energy enters ecosystem Photosynthesis – converts light energy to chemical energy Cellular respiration – harvests food energy to produce ATP C 6 H 12 O 6 Glucose O 2 Oxygen CO 2 Carbon dioxide H 2 O Water drives cellular work Heat energy exits ecosystem ATP Figure 6.2 Energy flow and chemical cycling in ecosystems.

9. CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY Cellular respiration is: –The main way that chemical energy is harvested from food and converted to ATP –An aerobic process—it requires oxygen Cellular respiration and breathing are closely related. –Cellular respiration requires a cell to exchange gases with its surroundings. –Cells take in oxygen gas. –Cells release waste carbon dioxide gas. –Breathing exchanges these same gases between the blood and outside air. © 2010 Pearson Education, Inc.

10. Breathing Cellular respiration Muscle cells Lungs CO 2 O2O2 O2O2 Figure 6.3 When you inhale you breathe in O 2 the O 2 is delivered to your cells where it is used for respiration. CO 2, a waste, of cellular respiration, diffuses into the blood where it is exhaled by the lungs.

11. © 2010 Pearson Education, Inc. The Overall Equation for Cellular Respiration A common fuel molecule for cellular respiration is glucose. The overall equation for what happens to glucose during cellular respiration:

12. C 6 H 12 O 6 CO 2 O2O2 H2OH2O GlucoseOxygenCarbon dioxide Water  6 6 Reduction Oxidation Oxygen gains electrons (and hydrogens) Glucose loses electrons (and hydrogens) Figure 6.UN02

13. © 2010 Pearson Education, Inc. The Role of Oxygen in Cellular Respiration Cellular respiration can produce up to 38 ATP molecules for each glucose molecule consumed. During cellular respiration, hydrogen and its bonding electrons change partners. –Hydrogen and its electrons go from sugar to oxygen, forming water. –This hydrogen transfer is why oxygen is so vital to cellular respiration.

14. © 2010 Pearson Education, Inc. Redox Reactions Chemical reactions that transfer electrons from one substance to another are called: –Oxidation-reduction reactions or –Redox reactions for short The loss of electrons during a redox reaction is called oxidation. The acceptance of electrons during a redox reaction is called reduction. During cellular respiration glucose is oxidized while oxygen is reduced.

15. © 2010 Pearson Education, Inc. Why does electron transfer to oxygen release energy? –When electrons move from glucose to oxygen, it is as though the electrons were falling. –This “fall” of electrons releases energy during cellular respiration. Cellular respiration is: –A controlled fall of electrons –A stepwise cascade much like going down a staircase

16. © 2010 Pearson Education, Inc. NADH and Electron Transport Chains The path that electrons take on their way down from glucose to oxygen involves many steps. The first step is an electron acceptor called NAD +. –The transfer of electrons from organic fuel to NAD + reduces it to NADH. The rest of the path consists of an electron transport chain, which: –Involves a series of redox reactions –Ultimately leads to the production of large amounts of ATP

17. Electrons from food Stepwise release of energy used to make Hydrogen, electrons, and oxygen combine to produce water Electron transport chain NADH NAD  HH HH ATP H2OH2O O2O2 22 2 2 2 1 ee ee ee ee ee ee Figure 6.5 <>

18. © 2010 Pearson Education, Inc. An Overview of Cellular Respiration Cellular respiration: –Is an example of a metabolic pathway, which is a series of chemical reactions in cells All of the reactions involved in cellular respiration can be grouped into three main stages: Stage 1: Glycolysis Stage 2: The citric acid cycle Stage 3: Electron transport

19. Cytoplasm Animal cellPlant cell Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid ATP Figure 6.6

20. Cytoplasm Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid ATP Figure 6.6a

21. © 2010 Pearson Education, Inc. The Three Stages of Cellular Respiration With the big-picture view of cellular respiration in mind, let’s examine the process in more detail.

22. © 2010 Pearson Education, Inc. Stage 1: Glycolysis A six-carbon glucose molecule is split in half to form two molecules of pyruvic acid. These two molecules then donate high energy electrons to NAD +, forming NADH.

23. Citric Acid Cycle Electron Transport Glycolysis ATP Figure 6.UN03

24. Energy investment phase Carbon atom Phosphate group High-energy electron Key Glucose 2 ATP 2 ADP INPUTOUTPUT Figure 6.7-1

25. 1. Energy investment phase Carbon atom Phosphate group High-energy electron Key Glucose 2 ATP 2 ADP INPUTOUTPUT 2. Energy harvest phase NADH NAD  Figure 6.7-2

26. 1. Energy investment phase Carbon atom Phosphate group High-energy electron Key Glucose 2 ATP 2 ADP INPUTOUTPUT 2. Energy harvest phase NADH NAD  2 ATP 2 ADP 2 Pyruvic acid Figure 6.7-3

27. © 2010 Pearson Education, Inc. Glycolysis: –Uses two ATP molecules per glucose to split the six-carbon glucose –Makes four additional ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP Thus, glycolysis produces a net of two molecules of ATP per glucose molecule.

28. ADP ATP P PP Enzyme Figure 6.8 – ATP synthesis by direct phosphate transfer.

29. © 2010 Pearson Education, Inc. Stage 2: The Citric Acid Cycle The citric acid cycle completes the breakdown of sugar. In the citric acid cycle, pyruvic acid from glycolysis is first “prepped.”

30. (from glycolysis)(to citric acid cycle) Oxidation of the fuel generates NADH Pyruvic acid loses a carbon as CO 2 Acetic acid attaches to coenzyme A Pyruvic acid Acetic acid Acetyl CoA Coenzyme A CoA CO 2 NAD  NADH INPUTOUTPUT Figure 6.9 – The link between glycolysis and the citric acid cycle: the conversion of pyruvic acid to acetyl CoA

31. © 2010 Pearson Education, Inc. The citric acid cycle: –Extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO 2 –Uses some of this energy to make ATP –Forms NADH and FADH 2

32. 3 NAD  ADP  P 3 NADH FADH 2 FAD Acetic acid Citric acid Acceptor molecule Citric Acid Cycle ATP 2 CO 2 INPUT OUTPUT Figure 6.10

33. © 2010 Pearson Education, Inc. Stage 3: Electron Transport Electron transport releases the energy your cells need to make the most of their ATP. The molecules of the electron transport chain are built into the inner membranes of mitochondria. –The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane. –These ions store potential energy.

34. © 2010 Pearson Education, Inc. When the hydrogen ions flow back through the membrane, they release energy. –The hydrogen ions flow through ATP synthase. –ATP synthase: –Takes the energy from this flow –Synthesizes ATP Cyanide is a deadly poison that: –Binds to one of the protein complexes in the electron transport chain –Prevents the passage of electrons to oxygen –Stops the production of ATP

35. © 2010 Pearson Education, Inc. The molecules of the electron transport chain are built into the inner membranes of mitochondria. –The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane. –These ions store potential energy.

36. Space between membranes Inner mitochondrial membrane Electron carrier Protein complex Electron flow MatrixElectron transport chain ATP synthase NADH NAD  FADH 2 FAD ATP ADP  H2OH2O O2O2 HH 1 2 HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH  2 P Figure 6.11

37. 1 2 Space between membranes Inner mitochondrial membrane Electron carrier Protein complex Electron flow MatrixElectron transport chain ATP synthase NADH NAD  FADH 2 FAD ATP ADP H2OH2O O2O2 HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH HH  2 P  Figure 6.11a

38. © 2010 Pearson Education, Inc. The Versatility of Cellular Respiration In addition to glucose, cellular respiration can “burn”: –Diverse types of carbohydrates –Fats –Proteins

39. Food PolysaccharidesFatsProteins SugarsGlycerolFatty acidsAmino acids Glycolysis Acetyl CoA Citric Acid Cycle Electron Transport ATP Figure 6.12

40. © 2010 Pearson Education, Inc. Adding Up the ATP from Cellular Respiration Cellular respiration can generate up to 38 molecules of ATP per molecule of glucose.

41. Cytoplasm Mitochondrion NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid 2 ATP 2 ATP NADH FADH 2 Maximum per glucose: 2 Acetyl CoA About 34 ATP by direct synthesis by direct synthesis by ATP synthase 22 2 6 About 38 ATP Figure 6.13 <>

42. © 2010 Pearson Education, Inc. FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY Some of your cells can actually work for short periods without oxygen. Fermentation is the anaerobic (without oxygen) harvest of food energy.

43. © 2010 Pearson Education, Inc. Fermentation in Human Muscle Cells After functioning anaerobically for about 15 seconds: –Muscle cells will begin to generate ATP by the process of fermentation Fermentation relies on glycolysis to produce ATP. Glycolysis: –Does not require oxygen –Produces two ATP molecules for each glucose broken down to pyruvic acid Pyruvic acid, produced by glycolysis, is –Reduced by NADH, producing NAD +, which keeps glycolysis going. In human muscle cells, lactic acid is a by-product.

44. Glucose 2 ATP 2 NAD  2 NADH 2 NAD   2 H  2 ADP 2 Pyruvic acid 2 Lactic acid Glycolysis INPUTOUTPUT  2 P Figure 6.14 Lactic acid after a long run

45. © 2010 Pearson Education, Inc. Fermentation in Microorganisms Fermentation alone is able to sustain many types of microorganisms. The lactic acid produced by microbes using fermentation is used to produce: –Cheese, sour cream, and yogurt dairy products –Soy sauce, pickles, olives –Sausage meat products

46. © 2010 Pearson Education, Inc. Yeast are a type of microscopic fungus that: –Use a different type of fermentation –Produce CO 2 and ethyl alcohol instead of lactic acid This type of fermentation, called alcoholic fermentation, is used to produce: –Beer –Wine –Breads

47. Glucose 2 ATP 2 NAD  2 NADH 2 NAD   2  2 P 2 Pyruvic acid 2 Ethyl alcohol Glycolysis INPUTOUTPUT 2 CO 2 released Bread with air bubbles produced by fermenting yeast Beer fermentation 2 ADP HH Figure 6.16 fin

48. Figure 6.17b