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PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE TAYLOR SIMON DICKEY HOGAN Chapter 6 Lecture by Edward J. Zalisko How.

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Presentation on theme: "PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE TAYLOR SIMON DICKEY HOGAN Chapter 6 Lecture by Edward J. Zalisko How."— Presentation transcript:

1 PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE TAYLOR SIMON DICKEY HOGAN Chapter 6 Lecture by Edward J. Zalisko How Cells Harvest Chemical Energy © 2015 Pearson Education, Inc.

2 Introduction Oxygen is a reactant in cellular respiration, the process that breaks down sugar and other food molecules and generates ATP, the energy currency in cells, and heat. Brown fat has a “short circuit” in its cellular respiration, which generates only heat, not ATP. Brown fat is important for heat production in small mammals, including humans. © 2015 Pearson Education, Inc.

3 C ELLULAR R ESPIRATION : A EROBIC H ARVESTING OF E NERGY C ELLULAR R ESPIRATION : A EROBIC H ARVESTING OF E NERGY

4 Photosynthesis and cellular respiration provide energy for life Life requires energy. In almost all ecosystems, energy ultimately comes from the sun. In photosynthesis, some of the energy in sunlight is captured by chloroplasts, atoms of carbon dioxide and water are rearranged, and sugar and oxygen are produced. © 2015 Pearson Education, Inc.

5 Photosynthesis and cellular respiration provide energy for life In cellular respiration, sugar is broken down to carbon dioxide and water and the cell captures some of the released energy to make ATP. Cellular respiration takes place in the mitochondria of eukaryotic cells. In these energy conversions, some energy is lost as heat. © 2015 Pearson Education, Inc.

6 Figure 6.1 Sunlight energy E COSYSTEM Photosynthesis in chloroplasts Organic molecules Cellular respiration in mitochondria ATP powers most cellular work Heat energy CO 2 + H 2 O + O 2 ATP

7 Breathing supplies O 2 for use in cellular respiration and removes CO 2 Respiration, as it relates to breathing, and cellular respiration are not the same. Respiration, in the breathing sense, refers to an exchange of gases. Usually an organism brings in oxygen from the environment and releases waste CO 2. Cellular respiration is the aerobic (oxygen-requiring) harvesting of energy from food molecules by cells. © 2015 Pearson Education, Inc.

8 Figure Lungs Transported in bloodstream Muscle cells carrying out Breathing Glucose + O 2 ➞ CO 2 + H 2 O + ATP Cellular Respiration O2O2 O2O2 CO 2

9 Cellular respiration banks energy in ATP molecules Cellular respiration is an exergonic (energy- releasing) process that transfers energy from the bonds in glucose to form ATP. © 2015 Pearson Education, Inc.

10 Cellular respiration banks energy in ATP molecules Cellular respiration can produce up to 32 ATP molecules for each glucose molecule, uses about 34% of the energy originally stored in glucose, and releases the other 66% as heat. This energy conversion efficiency is better than most energy conversion systems. Only about 25% of the energy in gasoline produces the kinetic energy of movement. © 2015 Pearson Education, Inc.

11 Glucose OxygenCarbon dioxide Water HeatATPH2OH2O6CO 2 6 O2O2 6 C 6 H 12 O 6

12 The human body uses energy from ATP for all its activities Your body requires a continuous supply of energy just to stay alive—to keep your heart pumping and you breathing. © 2015 Pearson Education, Inc.

13 A kilocalorie (kcal) is the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1  C, the same as a food Calorie, and used to measure the nutritional values indicated on food labels. © 2015 Pearson Education, Inc.

14 The average adult human needs about 2,200 kcal of energy per day. About 75% of these calories is used to maintain a healthy body. The remaining 25% is used to power physical activities. A balance of energy intake and expenditure is required to maintain a healthy weight. © 2015 Pearson Education, Inc.

15 Activity Running (8–9 mph) Dancing (fast) Bicycling (10 mph) Swimming (2 mph) Walking (4 mph) Walking (3 mph) Dancing (slow) Driving a car Sitting (writing) kcal consumed per hour by a 67.5-kg (150-lb) person* *Not including kcal needed for body maintenance

16 Cells capture energy from electrons “falling” from organic fuels to oxygen How do your cells extract energy from glucose? The answer involves the transfer of electrons during chemical reactions.

17 Cells capture energy from electrons “falling” from organic fuels to oxygen During cellular respiration, electrons are transferred from glucose to oxygen and energy is released. Oxygen attracts electrons very strongly. An electron loses potential energy when it is transferred to oxygen.

18 6.5 Cells capture energy from electrons “falling” from organic fuels to oxygen Energy can be released from glucose by simply burning it. This electron “fall” happens very rapidly. This energy is dissipated as heat and light and is not available to living organisms. © 2015 Pearson Education, Inc.

19 Cellular respiration is a more controlled descent of electrons and like rolling down an energy hill. Energy is released in small amounts and can be stored in the chemical bonds of ATP.

20 The movement of electrons from one molecule to another is an oxidation-reduction reaction, or redox reaction. In a redox reaction, the loss of electrons from one substance is called oxidation, the addition of electrons to another substance is called reduction, a molecule is oxidized when it loses one or more electrons, and a molecule is reduced when it gains one or more electrons.

21 Oxidation States of Carbon - 4 Highest Energy Least Stable +4 Lowest Energy Most Stable In Respiration, Carbon Carbon is Oxidized from its highest energy to a lower one. The energy coming out is eventually trapped and held in the cells as ATP. ATP provides this energy to run all of life’s processes. In Fats, most of the carbon atoms are at the -4 level. In Sugars and starches, they are in the -2 or 0 level.

22 Cells capture energy from electrons “falling” from organic fuels to oxygen A cellular respiration equation is helpful to show the changes in hydrogen atom distribution. Glucose loses its hydrogen atoms and becomes oxidized to CO 2. Oxygen gains hydrogen atoms and becomes reduced to H 2 O.

23 © 2015 Pearson Education, Inc. Loss of hydrogen atoms (becomes oxidized) Gain of hydrogen atoms (becomes reduced) (Glucose) C 6 H 12 O O 2 6 CO H 2 O + ATP + Heat

24 An important player in the process of oxidizing glucose is a coenzyme called NAD +, which accepts electrons and becomes reduced to NADH.

25 © 2015 Pearson Education, Inc. Becomes oxidized + 2 H Becomes reduced NAD + NADH H+H+ (carries) 2 electrons) + 2 H+H+ 2

26 NADH delivers electrons to a string of electron carrier molecules, which moves electrons down a hill. These carrier molecules constitute an electron transport chain. At the bottom of the hill is oxygen (1/2 O 2 ), which accepts two electrons, picks up two H +, and becomes reduced to water.

27 © 2015 Pearson Education, Inc. NAD + H+H+ NADH Energy released and available for making 2 2 O2O2 2 H2OH2O − 2 1 ATP

28 S TAGES OF C ELLULAR R ESPIRATION

29 Cellular respiration occurs in three main stages Cellular respiration consists of a sequence of steps that can be divided into three stages. Stage 1: Glycolysis Stage 2: Pyruvate oxidation and the citric acid cycle Stage 3: Oxidative phosphorylation

30 Cellular respiration occurs in three main stages Stage 1: Glycolysis occurs in the cytosol, begins cellular respiration, and breaks down glucose into two molecules of a three- carbon compound called pyruvate.

31 Cellular respiration occurs in three main stages Stage 2: Pyruvate oxidation and the citric acid cycle take place in mitochondria, oxidize pyruvate to a two-carbon compound, and supply the third stage with electrons. The cell makes a small amount of ATP during glycolysis and the citric acid cycle.

32 Cellular respiration occurs in three main stages Stage 3: Oxidative phosphorylation NADH and a related electron carrier, FADH 2, shuttle electrons to an electron transport chain embedded in the inner mitochondrial membrane. Most ATP produced by cellular respiration is generated by oxidative phosphorylation, which uses the energy released by the downhill fall of electrons from NADH and FADH 2 to oxygen to phosphorylate ADP.

33 Stage 3: Oxidative phosphorylation As the electron transport chain passes electrons down the energy hill, it also pumps hydrogen ions (H + ) across the inner mitochondrial membrane, into the narrow intermembrane space, and produces a concentration gradient of H + across the membrane. In chemiosmosis, the potential energy of this concentration gradient is used to make ATP.

34 © 2015 Pearson Education, Inc. Figure Electrons carried by NADH FADH 2 ATP Glycolysis GlucosePyruvate Pyruvate Oxidation Citric Acid Cycle Substrate-level phosphorylation Oxidative phosphorylation Oxidative Phosphorylation (Electron transport and chemiosmosis) C YTOSOL M ITOCHONDRION

35 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate In glycolysis, a single molecule of glucose is enzymatically cut in half through a series of steps, two molecules of pyruvate are produced, two molecules of NAD + are reduced to two molecules of NADH, and there is a net gain of two molecules of ATP. © 2015 Pearson Education, Inc.

36 Glucose 2 ADP 2 Pyruvate ATP 2 NADH NAD + +2 H P

37 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate ATP is formed in glycolysis by substrate-level phosphorylation during which an enzyme transfers a phosphate group from a substrate molecule to ADP and ATP is formed. The compounds that form between the initial reactant, glucose, and the final product, pyruvate, are known as intermediates. © 2015 Pearson Education, Inc.

38 Enzyme ADP SubstrateProduct P P P ATP

39 The steps of glycolysis have two main phases. In steps 1–4, the energy investment phase, energy is consumed as two ATP molecules are used to energize a glucose molecule, which is then split into two small sugars. In steps 5–9, the energy payoff phase, two NADH molecules are produced for each initial glucose molecule and four ATP molecules are generated. There is a net gain of two ATP molecules for each glucose molecule that enters glycolysis.

40 © 2015 Pearson Education, Inc. Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Glyceraldehyde 3-phosphate (G3P) ENERGY INVESTMENT PHASE Step P ATP ADP Step A six-carbon intermediate splits into two three-carbon intermediates. ATP ADP P PP P P Steps–Glucose is energized, using ATP.

41 © 2015 Pearson Education, Inc Glyceraldehyde 3-phosphate (G3P) ATP ADP P ATP ADP H2OH2OH2OH2O NAD + NADH + H + P P P P P P P P P P P P P ENERGY PAYOFF PHASE 1,3-Bisphosphoglycerate 3-Phosphoglycerate 2-Phosphoglycerate Phosphoenolpyruvate (PEP) Pyruvate Step A redox reaction generates NADH. Steps–ATP and pyruvate are produced.

42 6.8 Pyruvate is oxidized in preparation for the citric acid cycle The pyruvate formed in glycolysis is transported from the cytosol into a mitochondrion where the citric acid cycle and oxidative phosphorylation will occur. Two molecules of pyruvate are produced for each molecule of glucose that enters glycolysis. © 2015 Pearson Education, Inc.

43 Pyruvate does not enter the citric acid cycle but undergoes some chemical grooming in which a carboxyl group is removed and given off as CO 2, the two-carbon compound remaining is oxidized while a molecule of NAD + is reduced to NADH, and coenzyme A joins with the two-carbon group to form acetyl coenzyme A, abbreviated as acetyl CoA. Then two molecules of acetyl CoA enter the citric acid cycle.

44 © 2015 Pearson Education, Inc. Pyruvate NAD + NADH+ H Coenzyme A CO 2 CoA Acetyl coenzyme A

45 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH 2 molecules The citric acid cycle is also called the Krebs cycle (after the German- British researcher Hans Krebs, who worked out much of this pathway in the 1930s), completes the oxidation of organic molecules, and generates many NADH and FADH 2 molecules.

46 © 2015 Pearson Education, Inc. Citric Acid Cycle NAD + NADH + 3 H + CO 2 CoA Acetyl CoA FADH 2 FAD ATP PADP +

47 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH 2 molecules During the citric acid cycle the two-carbon group of acetyl CoA is joined to a four-carbon compound, forming citrate, citrate is degraded back to the four-carbon compound, two CO 2 are released, and one ATP, three NADH, and one FADH 2 are produced.

48 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH 2 molecules Remember that the citric acid cycle processes two molecules of acetyl CoA for each initial glucose. Thus, after two turns of the citric acid cycle, the overall yield per glucose molecule is 2 ATP, 6 NADH, and 2 FADH 2. © 2015 Pearson Education, Inc.

49 The citric acid cycle completes the oxidation of organic molecules, generating many NADH and FADH 2 molecules Thus, after glycolysis and the citric acid cycle, the cell has gained 4 ATP, 10 NADH, and 2 FADH 2. To harvest the energy banked in NADH and FADH 2, these molecules must shuttle their high- energy electrons to an electron transport chain.

50 © 2015 Pearson Education, Inc. CoA Acetyl CoA 2 carbons enter cycle Oxaloacetate Step Acetyl CoA stokes the furnace. 11 Citric Acid Cycle

51 © 2015 Pearson Education, Inc. Citric Acid Cycle NAD + NADH + H + CO 2 CoA Acetyl CoA ATP P ADP + CO 2 + H + 2 carbons enter cycle Citrate leaves cycle Alpha-ketoglutarate Succinate Oxaloacetate leaves cycle Step Acetyl CoA stokes the furnace. Steps– NADH, ATP, and CO 2 are generated during redox reactions NAD + NADH

52 © 2015 Pearson Education, Inc. Figure 6.9b-3 Citric Acid Cycle NAD + NADH + H + CO 2 CoA Acetyl CoA FADH 2 FAD ATP P ADP + CO 2 + H + NAD + NADH H2OH2O 2 carbons enter cycle Citrate leaves cycle Alpha-ketoglutarate Succinate Fumarate Malate Oxaloacetate leaves cycle Step Acetyl CoA stokes the furnace. Steps– NADH, ATP, and CO 2 are generated during redox reactions. Steps– Further redox reactions generate FADH 2 and more NADH NAD + NADH

53 Most ATP production occurs by oxidative phosphorylation The final stage of cellular respiration is oxidative phosphorylation, which involves electron transport and chemiosmosis and requires an adequate supply of oxygen. The arrangement of electron carriers built into a membrane makes it possible to create an H + concentration gradient across the membrane and then use the energy of that gradient to drive ATP synthesis.

54 6.10 Most ATP production occurs by oxidative phosphorylation Electrons from NADH and FADH 2 travel down the electron transport chain to O 2, the final electron acceptor. Oxygen picks up H +, which forms water. Energy released by these redox reactions is used to pump H + from the mitochondrial matrix into the intermembrane space. © 2015 Pearson Education, Inc.

55 In chemiosmosis, the H + diffuses back across the inner membrane, through ATP synthase complexes, driving the synthesis of ATP.

56 © 2015 Pearson Education, Inc. Figure 6.10a OUTER MITOCHONDRIAL MEMBRANE Q FADH 2 FAD ATPP ADP + H+H+ NAD + NADH H2OH2O O2O2 H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Cyt c − II III I ATP synthase Protein complex of electron carriers Mobile electron carriers Intermem- brane space Inner mito- chondrial membrane Mito- chondrial matrix Electron flow Electron Transport Chain Oxidative Phosphorylation Chemiosmosis IV

57 © 2015 Pearson Education, Inc. Figure 6.10b INTERMEMBRANE SPACE MITOCHONDRIAL MATRIX Rotor Internal rod Catalytic knob ATP ADP P H+H+ +

58 Scientists have discovered heat-producing, calorie-burning brown fat in adults Mitochondria in brown fat can burn fuel and produce heat without making ATP. Ion channels spanning the inner mitochondrial membrane allow H + to flow freely across the membrane and dissipate the H + gradient that the electron transport chain produced, which does not allow ATP synthase to make ATP.

59 Scientific studies of humans indicate that brown fat may be present in most people and when activated by cold environments, the brown fat of lean individuals is more active.

60 Review: Each molecule of glucose yields many molecules of ATP Recall that the energy payoff of cellular respiration involves 1.glycolysis, 2.alteration of pyruvate, 3.the citric acid cycle, and 4.oxidative phosphorylation. © 2015 Pearson Education, Inc.

61 Review: Each molecule of glucose yields many molecules of ATP The total yield is about 32 ATP molecules per glucose molecule. The number of ATP molecules cannot be stated exactly for several reasons. The NADH produced in glycolysis passes its electrons across the mitochondrial membrane to either NAD + or FAD. Because FADH 2 adds its electrons farther along the electron transport chain, it contributes less to the H + gradient and thus generates less ATP. Some of the energy of the H + gradient may be used for work other than ATP production, such as the active transport of pyruvate into the mitochondrion. © 2015 Pearson Education, Inc.

62 NADH FADH 2 CO 2 Maximum per glucose: + 2 ATP Glycolysis Glucose 2 Pyruvate Pyruvate Oxidation 2 Acetyl CoA Citric Acid Cycle by substrate-level phosphorylation by oxidative phosphorylation Oxidative Phosphorylation (electron transport and chemiosmosis) C YTOSOL MITOCHONDRION 2 NADH ATP + about 28 ATP About 32 ATP O2O2 H2OH2O

63 F ERMENTATION : A NAEROBIC H ARVESTING OF E NERGY

64 Fermentation enables cells to produce ATP without oxygen Fermentation is a way of harvesting chemical energy that does not require oxygen. Fermentation uses glycolysis, produces two ATP molecules per glucose, and reduces NAD + to NADH. Fermentation also provides an anaerobic path for recycling NADH back to NAD +. © 2015 Pearson Education, Inc.

65 Fermentation enables cells to produce ATP without oxygen Your muscle cells and certain bacteria can regenerate NAD + through lactic acid fermentation, in which NADH is oxidized back to NAD + and pyruvate is reduced to lactate.

66 © 2015 Pearson Education, Inc. Glucose 2 ADP 2NADH 2NAD + 2 ATP 2NADH 2NAD + + 2P Glycolysis 2 Pyruvate 2 Lactate

67 Fermentation enables cells to produce ATP without oxygen Lactate is carried by the blood to the liver, where it is converted back to pyruvate and oxidized in the mitochondria of liver cells. The dairy industry uses lactic acid fermentation by bacteria to make cheese and yogurt. Other types of microbial fermentation turn soybeans into soy sauce and cabbage into sauerkraut.

68 The baking and winemaking industries have used alcohol fermentation for thousands of years. In this process, yeast (single-celled fungi) oxidize NADH back to NAD + and convert pyruvate to CO 2 and ethanol.

69 © 2015 Pearson Education, Inc. Glucose 2 ADP 2NADH 2NAD + 2 ATP 2NADH 2NAD + + 2P Glycolysis 2 Pyruvate 2 Ethanol 2 CO 2

70 Obligate anaerobes require anaerobic conditions, are poisoned by oxygen, and live in stagnant ponds and deep soils. Facultative anaerobes can make ATP by fermentation or oxidative phosphorylation and include yeasts and many bacteria.

71 © 2015 Pearson Education, Inc. Figure 6.13c-1

72 Glycolysis evolved early in the history of life on Earth Glycolysis is the universal energy-harvesting process of life. The role of glycolysis in fermentation and respiration dates back to life long before oxygen was present, when only prokaryotes inhabited the Earth, about 3.5 billion years ago. © 2015 Pearson Education, Inc.

73 Glycolysis evolved early in the history of life on Earth The ancient history of glycolysis is supported by its occurrence in all the domains of life and location within the cell, using pathways that do not involve any membrane-enclosed organelles of the eukaryotic cell. © 2015 Pearson Education, Inc.

74 C ONNECTIONS B ETWEEN M ETABOLIC P ATHWAYS

75 Cells use many kinds of organic molecules as fuel for cellular respiration Although glucose is considered to be the primary source of sugar for respiration and fermentation, ATP is generated using carbohydrates, fats, and proteins.

76 Cells use many kinds of organic molecules as fuel for cellular respiration Fats make excellent cellular fuel because they contain many hydrogen atoms and thus many energy-rich electrons and yield more than twice as much ATP per gram as a gram of carbohydrate. Proteins can also be used for fuel, although your body preferentially burns sugars and fats first. © 2015 Pearson Education, Inc.

77 Food, such as peanuts Carbohydrates Fats Proteins Oxidative Phosphorylation SugarsGlycerolFatty acidsAmino acids Amino groups GlucoseG3PPyruvate Glycolysis Acetyl CoA Citric Acid Cycle ATP

78 Organic molecules from food provide raw materials for biosynthesis A cell must be able to make its own molecules to build its structures and perform its functions. Food provides the raw materials your cells use for biosynthesis, the production of organic molecules, using energy-requiring metabolic pathways.

79 © 2015 Pearson Education, Inc. Figure Cells, tissues, organisms ATP needed to drive biosynthesis Carbohydrates Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups PyruvateG3PGlucose Glucose Synthesis Acetyl CoA Citric Acid Cycle ATP

80 Organic molecules from food provide raw materials for biosynthesis Metabolic pathways are often regulated by feedback inhibition in which an accumulation of product suppresses the process that produces the product.

81 R EVIEW

82 You should now be able to 1.Compare the processes and locations of cellular respiration and photosynthesis. 2.Explain how breathing and cellular respiration are related. 3.Provide the overall chemical equation for cellular respiration. 4.Explain how the human body uses its daily supply of ATP. © 2015 Pearson Education, Inc.

83 You should now be able to 5.Explain how the energy in a glucose molecule is released during cellular respiration. 6.Explain how redox reactions are used in cellular respiration. 7.Describe the general roles of dehydrogenase, NADH, and the electron transport chain in cellular respiration. 8.Compare the reactants, products, and energy yield of the three stages of cellular respiration. © 2015 Pearson Education, Inc.

84 You should now be able to 9.Describe the special function of brown fat. 10.Compare the reactants, products, and energy yield of alcohol and lactic acid fermentation. 11.Distinguish between strict anaerobes and facultative anaerobes. 12.Explain how carbohydrates, fats, and proteins are used as fuel for cellular respiration. © 2015 Pearson Education, Inc.

85 Figure 6.UN01 Glucose Oxygen Carbon dioxide Water HeatATPH2OH2O6CO 2 6O2O2 6C 6 H 12 O 6 +

86 © 2015 Pearson Education, Inc. Figure 6.UN02 Electrons carried by NADHFADH 2 ATP Glycolysis GlucosePyruvate Pyruvate Oxidation Citric Acid Cycle Substrate-level phosphorylation Oxidative phosphorylation Oxidative Phosphorylation (Electron transport and chemiosmosis) CYTOSOLMITOCHONDRION

87 © 2015 Pearson Education, Inc. Figure 6.UN03 Cellular respiration glucose and organic fuels cellular work chemiosmosis H + gradient ATP (a) (b) (c) (d) (e) (f) (g) generates has three stagesoxidizes uses produce some produces many energy for by a process called uses H + diffuse through ATP synthase pumps H + to create uses to pull electrons down to C 6 H 12 O 6


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