Chapter 6 Cellular Respiration: Obtaining Energy from Food

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1 Chapter 6 Cellular Respiration: Obtaining Energy from Food PowerPoint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with Physiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko 2013 Pearson Education, Inc.

2 ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE Animals depend on plants to convert the energy of sunlight to chemical energy of sugars and other organic molecules we consume as food. Photosynthesis uses light energy from the sun to power a chemical process and make organic molecules 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 Pearson Education, Inc.

4 Producers and Consumers Autotrophs are producers because ecosystems depend upon them for food. Heterotrophs are consumers because they eat plants or other animals Pearson Education, Inc.

5 Figure 6.1

6 Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide (CO 2 ) and water (H 2 O). 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 Pearson Education, Inc.

7 Chemical Cycling between Photosynthesis and Cellular Respiration 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, and oxygen gas Pearson Education, Inc.

8 Chemical Cycling between Photosynthesis and Cellular Respiration Plant and animal cells perform cellular respiration, a chemical process that primarily occurs in mitochondria, harvests energy stored in organic molecules, uses oxygen, and generates ATP Pearson Education, Inc.

9 Chemical Cycling between Photosynthesis and Cellular Respiration The waste products of cellular respiration are CO 2 and H 2 O, used in photosynthesis Pearson Education, Inc.

10 Chemical Cycling between Photosynthesis and Cellular Respiration Animals perform only cellular respiration. Plants perform photosynthesis and cellular respiration Pearson Education, Inc.

11 Chemical Cycling between Photosynthesis and Cellular Respiration Plants usually make more organic molecules than they need for fuel. This surplus provides material that can be used for the plant to grow or stored as starch in potatoes Pearson Education, Inc.

12 Figure 6.2 Sunlight energy enters ecosystem Photosynthesis C 6 H 12 O 6 CO 2 O 2 H 2 O Cellular respiration ATP drives cellular work Heat energy exits ecosystem

13 CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY Cellular respiration is the main way that chemical energy is harvested from food and converted to ATP and an aerobic process it requires oxygen Pearson Education, Inc.

14 CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY 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 Pearson Education, Inc.

15 Figure 6.3 O 2 CO 2 Breathing Lungs O 2 CO 2 Cellular respiration Muscle cells

16 The Simplified Equation for Cellular Respiration A common fuel molecule for cellular respiration is glucose. Cellular respiration can produce up to 32 ATP molecules for each glucose molecule consumed. The overall equation for what happens to glucose during cellular respiration is glucose & oxygen è CO 2, H 2 O, & a release of energy Pearson Education, Inc.

17 Figure 6.UN01 C 6 H 12 O CO 2 6 H 2 O ATP O 2 Glucose Oxygen Carbon dioxide Water Energy

18 The Role of Oxygen in Cellular Respiration During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product Pearson Education, Inc.

19 Redox Reactions Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions or redox reactions for short Pearson Education, Inc.

20 Redox Reactions The loss of electrons during a redox reaction is oxidation. The acceptance of electrons during a redox reaction is reduction. During cellular respiration glucose is oxidized and oxygen is reduced Pearson Education, Inc.

21 Figure 6.UN02 Oxidation Glucose loses electrons (and hydrogens) C 6 H 12 O 6 6 O 2 6 CO 2 6 Glucose Oxygen Carbon dioxide H 2 O Water Reduction Oxygen gains electrons (and hydrogens)

22 Redox Reactions 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 Pearson Education, Inc.

23 Redox Reactions Cellular respiration is a controlled fall of electrons and a stepwise cascade much like going down a staircase Pearson Education, Inc.

24 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 +. NAD is made by cells from niacin, a B vitamin. The transfer of electrons from organic fuel to NAD + reduces it to NADH Pearson Education, Inc.

25 NADH and Electron Transport Chains The rest of the path consists of an electron transport chain, which involves a series of redox reactions and ultimately leads to the production of large amounts of ATP Pearson Education, Inc.

26 Figure 6.5 e - e - Electrons from food NAD + e - e - NADH Stepwise release of energy used to make 2 2 e - ATP 2 e O 2 Hydrogen, electrons, and oxygen combine to produce water H 2 O

27 Figure 6.5a 2 2 e - ATP Stepwise release of energy used to make ATP Electron transport chain 2 e O 2 Hydrogen, electrons, and oxygen combine to produce water H 2 O

28 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: 1. glycolysis, 2. the citric acid cycle, and 3. electron transport. BioFlix Animation: Cellular Respiration 2013 Pearson Education, Inc.

29 Figure 6.6 Mitochondrion Cytoplasm Cytoplasm Animal cell Plant cell Cytoplasm Mitochondrion High-energy electrons via carrier molecules Glycolysis 2 Glucose Pyruvic acid Citric Acid Cycle Electron Transport ATP ATP ATP

30 Figure 6.6a Cytoplasm Mitochondrion Glycolysis 2 Glucose Pyruvic acid Citric Acid Cycle High-energy electrons via carrier molecules Electron Transport ATP ATP ATP

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

32 Stage 1: Glycolysis 1. A six-carbon glucose molecule is split in half to form two molecules of pyruvic acid. 2. These two molecules then donate high energy electrons to NAD +, forming NADH Pearson Education, Inc.

33 Figure 6.7 INPUT NADH OUTPUT P NAD + P 2 ADP 2 ATP 2 ATP 2 ADP P 2 P 3 2 Pyruvic acid 1 P P 2 P 3 Glucose NAD + NADH P 2 ADP 2 ATP Energy investment phase Key Carbon atom P Phosphate group High-energy electron Energy harvest phase

34 Figure 6.7a INPUT OUTPUT 2 Pyruvic acid Glucose

35 Figure 6.7b-1 P 2 ATP 2 ADP 1 P Energy investment phase

36 Figure 6.7b-3 NADH P NAD + P 2 ADP 2 ATP 2 ATP 2 ADP P 2 P 3 1 P P 2 P 3 NAD + NADH P 2 ADP 2 ATP Energy investment phase Energy harvest phase

37 Stage 1: Glycolysis 3. Glycolysis uses two ATP molecules per glucose to split the six-carbon glucose and 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 Pearson Education, Inc.

38 Figure 6.8 Enzyme P ADP ATP P P

39 Stage 2: The Citric Acid Cycle In the citric acid cycle, pyruvic acid from glycolysis is first groomed. Each pyruvic acid loses a carbon as CO 2. The remaining fuel molecule, with only two carbons left, is acetic acid. Oxidation of the fuel generates NADH Pearson Education, Inc.

40 Stage 2: The Citric Acid Cycle Finally, each acetic acid is attached to a molecule called coenzyme A to form acetyl CoA. The CoA escorts the acetic acid into the first reaction of the citric acid cycle. The CoA is then stripped and recycled Pearson Education, Inc.

41 Figure 6.9 INPUT (from glycolysis) 2 NAD + Oxidation of the fuel generates NADH NADH OUTPUT (to citric acid cycle) CoA Pyruvic acid 1 Pyruvic acid loses a carbon as CO 2 CO 2 Acetic acid Coenzyme A 3 Acetic acid attaches to coenzyme A Acetyl CoA

42 Figure 6.9a INPUT (from glycolysis) OUTPUT (to citric acid cycle) CoA Pyruvic acid Acetyl CoA

43 Figure 6.9b 2 NAD + Oxidation of the fuel generates NADH NADH OUTPUT 1 Pyruvic acid loses a carbon as CO 2 CO 2 Acetic acid Coenzyme A 3 Acetic acid attaches to coenzyme A

44 Stage 2: The Citric Acid Cycle 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, and forms NADH and FADH 2. Blast Animation: Harvesting Energy: Krebs Cycle 2013 Pearson Education, Inc.

45 Figure 6.10 INPUT Citric acid OUTPUT 1 Acetic acid 2 CO 2 2 ADP + P 3 NAD + Citric Acid Cycle ATP 3 NADH 3 4 FAD FADH Acceptor molecule

46 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, which uses energy released by the fall of electrons to pump hydrogen ions across the inner mitochondrial membrane, and uses these ions to store potential energy Pearson Education, Inc.

47 Stage 3: Electron Transport 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 and synthesizes ATP Pearson Education, Inc.

48 Figure 6.11 Space between membranes Protein complex Electron carrier 3 5 Inner mitochondrial membrane Electron flow FADH 2 NADH NAD + 1 FAD 2 2 H 2 O 6 4 Matrix Electron transport chain ATP synthase 1 2 O 2 ADP P ATP

49 Figure 6.11a Space between membranes Protein complex Electron carrier 3 5 Inner mitochondrial membrane Electron flow FADH 2 NADH NAD + 1 FAD + H H+ H+ 2 Matrix Electron transport chain ATP synthase 1 2 O H 2 O ADP P 6 ATP

50 Figure 6.11b Space between membranes H Electron carrier 3 Protein complex Inner mitochondrial membrane Electron flow FADH 2 2 FAD 1 2 O 2 2 NADH NAD H+ Matrix Electron transport chain

51 Figure 6.11c O 2 2 H 2 O 6 4 ADP P ATP ATP synthase

52 Stage 3: Electron Transport 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, and stops the production of ATP Pearson Education, Inc.

53 The Results of Cellular Respiration Cellular respiration can generate up to 32 molecules of ATP per molecule of glucose Pearson Education, Inc.

54 Figure 6.12 Cytoplasm Mitochondrion 2 NADH 2 NADH 6 NADH 2 FADH 2 Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport Maximum per glucose: 2 ATP 2 ATP About 28 ATP About 32 ATP by direct synthesis by direct synthesis by ATP synthase

55 Figure 6.12a Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport 2 ATP 2 ATP About 28 ATP by direct synthesis by direct synthesis by ATP synthase

56 The Results of Cellular Respiration In addition to glucose, cellular respiration can burn diverse types of carbohydrates, fats, and proteins Pearson Education, Inc.

57 Figure 6.13 Food Polysaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Glycolysis Acetyl CoA Citric Acid Cycle Electron Transport ATP

58 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 Pearson Education, Inc.

59 Fermentation in Human Muscle Cells After functioning anaerobically for about 15 seconds, muscle cells begin to generate ATP by the process of fermentation. Fermentation relies on glycolysis to produce ATP. Glycolysis does not require oxygen and produces two ATP molecules for each glucose broken down to pyruvic acid Pearson Education, Inc.

60 Fermentation in Human Muscle Cells 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. Animation: Fermentation Overview 2013 Pearson Education, Inc.

61 Figure 6.14 INPUT 2 ADP 2 P 2 ATP OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid 2 2 Lactic acid

62 Figure 6.14a INPUT 2 ADP 2 P 2 ATP OUTPUT Glycolysis 2 NAD + 2 NADH 2 NADH 2 NAD + Glucose 2 Pyruvic acid 2 2 Lactic acid

63 The Process of Science: What Causes Muscle Burn? Observation: Muscles produce lactic acid under anaerobic conditions. Question: Does the buildup of lactic acid cause muscle fatigue? 2013 Pearson Education, Inc.

64 The Process of Science: What Causes Muscle Burn? Hypothesis: The buildup of lactic acid would cause muscle activity to stop. Experiment: Tested frog muscles under conditions when lactic acid could and could not diffuse away Pearson Education, Inc.

65 Figure 6.15 Battery + Force measured Battery + Force measured Frog muscle stimulated by electric current Solution prevents diffusion of lactic acid Solution allows diffusion of lactic acid; muscle can work for twice as long

66 The Process of Science: What Causes Muscle Burn? Results: When lactic acid could diffuse away, performance improved greatly. Conclusion: Lactic acid accumulation is the primary cause of failure in muscle tissue. However, recent evidence suggests that the role of lactic acid in muscle function remains unclear Pearson Education, Inc.

67 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, soy sauce, pickles, and olives, and sausage meat products Pearson Education, Inc.

68 Fermentation in Microorganisms Yeast is a microscopic fungus that uses a different type of fermentation and produces CO 2 and ethyl alcohol instead of lactic acid. This type of fermentation, called alcoholic fermentation, is used to produce beer, wine, and breads Pearson Education, Inc.

69 Figure 6.16 INPUT 2 ADP + 2 P 2 ATP 2 CO 2 released OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid Ethyl alcohol

70 Figure 6.16a INPUT 2 ADP + 2 P 2 ATP 2 CO 2 released OUTPUT Glycolysis Glucose 2 NAD + 2 NADH 2 NADH 2 NAD + 2 Pyruvic acid +2 2 Ethyl alcohol

71 Figure 6.16b

72 Evolution Connection: Life before and after Oxygen Glycolysis could be used by ancient bacteria to make ATP when little oxygen was available, and before organelles evolved. Today, glycolysis occurs in almost all organisms and is a metabolic heirloom of the first stage in the breakdown of organic molecules Pearson Education, Inc.

73 Figure Billions of years ago O 2 present in Earth s atmosphere First eukaryotic organisms Atmospheric oxygen reaches 10% of modern levels Atmospheric oxygen first appears Oldest prokaryotic fossils 4.5 Origin of Earth

74 Figure 6.17a Billions of years ago O 2 present in Earth s atmosphere First eukaryotic organisms Atmospheric oxygen reaches 10% of modern levels Atmospheric oxygen first appears Oldest prokaryotic fossils 4.5 Origin of Earth

75 Figure 6.17b

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

77 Figure 6.UN04 Glycolysis Citric Acid Cycle Electron Transport ATP ATP ATP

78 Figure 6.UN05 Glycolysis Citric Acid Cycle Electron Transport ATP ATP ATP

79 Figure 6.UN06 C 6 H 12 O 6 Heat Sunlight O 2 ATP Photosynthesis Cellular respiration CO 2 H 2 O

80 Figure 6.UN07 O 2 C 6 H 12 O CO H 2 O + Approx. 32 ATP

81 Figure 6.UN08 Oxidation Glucose loses electrons (and hydrogens) C 6 H 12 O 6 CO 2 Electrons (and hydrogens) ATP O 2 Reduction Oxygen gains electrons (and hydrogens) H 2 O

82 Figure 6.UN09 Mitochondrion O 2 6 NADH 2 NADH 2 NADH 2 FADH 2 Glycolysis 2 Glucose Pyruvic acid 2 Acetyl CoA Citric Acid Cycle Electron Transport 2 CO 2 4 CO 2 H 2 O 2 ATP by direct synthesis by direct synthesis 2 ATP About 28 ATP by ATP synthase About 32 ATP