Chapter 6 Cellular Respiration: Obtaining Energy from Food Biology and Society: Marathoners versus Sprinters Sprinters do not usually compete at short and long distances. 5 Natural differences in the muscles of these athletes favor sprinting or long-distance running. oweroint Lectures for Campbell Essential Biology, Fifth Edition, and Campbell Essential Biology with hysiology, Fourth Edition Eric J. Simon, Jean L. Dickey, and Jane B. Reece Lectures by Edward J. Zalisko Figure 6.0 6 Biology and Society: Marathoners versus Sprinters 7 The muscles that move our legs contain two main types of muscle fibers:. slow-twitch and. fast-twitch.
Biology and Society: Marathoners versus Sprinters 8 Biology and Society: Marathoners versus Sprinters 9 Slow-twitch fibers Fast-twitch fibers last longer, contract more quickly and powerfully, do not generate a lot of quick power, and fatigue more quickly, and generate AT using oxygen (aerobically). can generate AT without using oxygen (anaerobically). All human muscles contain both types of fibers but in different ratios. ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSHERE Animals depend on plants to convert the energy of sunlight to chemical energy of sugars and other organic molecules we consume as food. hotosynthesis uses light energy from the sun to power a chemical process and make organic molecules. 0 roducers and Consumers lants 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.
roducers and Consumers Chemical Cycling between hotosynthesis and Cellular Respiration Autotrophs are producers because ecosystems depend upon them for food. Heterotrophs are consumers because they eat plants or other animals. The ingredients for photosynthesis are carbon dioxide (CO ) and water (H O). CO is obtained from the air by a plant s leaves. H O is obtained from the damp soil by a plant s roots. Chemical Cycling between hotosynthesis and Cellular Respiration 4 Chemical Cycling between hotosynthesis and Cellular Respiration 5 Chloroplasts in the cells of leaves use light energy to rearrange the atoms of CO and H O, which produces sugars (such as glucose), other organic molecules, and oxygen gas. lant and animal cells perform cellular respiration, a chemical process that primarily occurs in mitochondria, harvests energy stored in organic molecules, uses oxygen, and generates AT.
Chemical Cycling between hotosynthesis and Cellular Respiration 6 Chemical Cycling between hotosynthesis and Cellular Respiration 7 The waste products of cellular respiration are Animals perform only cellular respiration. CO and H O, lants perform used in photosynthesis. photosynthesis and cellular respiration. Chemical Cycling between hotosynthesis and Cellular Respiration 8 Figure 6. Sunlight energy enters ecosystem 9 lants usually make more organic molecules than they need for fuel. This surplus provides material that can be hotosynthesis C 6 H O 6 CO used for the plant to grow or stored as starch in potatoes. O H O Cellular respiration AT drives cellular work Heat energy exits ecosystem
CELLULAR RESIRATION: AEROBIC HARVEST OF FOOD ENERGY 0 CELLULAR RESIRATION: AEROBIC HARVEST OF FOOD ENERGY Cellular respiration is the main way that chemical energy is harvested from food and converted to AT and 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. Figure 6. O CO The Simplified Equation for Cellular Respiration Breathing Lungs A common fuel molecule for cellular respiration is glucose. O CO Cellular respiration can produce up to AT molecules for each glucose molecule consumed. Cellular respiration Muscle cells The overall equation for what happens to glucose during cellular respiration is glucose & oxygen CO, H O, & a release of energy.
Figure 6.UN0 4 The Role of Oxygen in Cellular Respiration 5 During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product. C 6 H O 6 6 6 CO 6 H O AT O Glucose Oxygen Carbon dioxide Water Energy Redox Reactions 6 Redox Reactions 9 Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions or redox reactions for short. 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.
Figure 6.4 H O 0 Redox Reactions Cellular respiration is a controlled fall of electrons and Release of heat energy a stepwise cascade much like going down a staircase. H O and Transport Chains and Transport Chains The path that electrons take on their way down from glucose to oxygen involves many steps. The rest of the path consists of an electron transport chain, which 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. involves a series of redox reactions and ultimately leads to the production of large amounts of AT.
Figure 6.5 e e NAD + s from food e e Stepwise release of energy used to make 4 Figure 6.5a e AT Stepwise release of energy used to make AT 5 e AT transport chain e e O O Hydrogen, electrons, and oxygen combine to produce water H O Hydrogen, electrons, and oxygen combine to produce water H O An Overview of Cellular Respiration 6 7 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:. glycolysis,. the citric cycle, and. electron transport. BioFlix Animation: Cellular Respiration
Figure 6.6 Mitochondrion Cytoplasm 8 Figure 6.6a 9 Cytoplasm Cytoplasm Mitochondrion Cytoplasm Glycolysis Glucose yruvic Animal cell Citric Acid Cycle High-energy electrons via carrier molecules lant cell Mitochondrion Transport Glycolysis Glucose yruvic Citric Acid Cycle High-energy electrons via carrier molecules Transport AT AT AT AT AT AT The Three Stages of Cellular Respiration 40 Stage : Glycolysis 4 With the big-picture view of cellular respiration in mind, let s examine the process in more detail.. A six-carbon glucose molecule is split in half to form two molecules of pyruvic.. These two molecules then donate high energy electrons to NAD +, forming.
Figure 6.7 4 Figure 6.7a 4 INUT NAD + AD AT OUTUT INUT OUTUT AT AD yruvic Glucose NAD + AD AT yruvic Energy investment phase Key Carbon atom hosphate group High-energy electron Energy harvest phase Glucose Figure 6.7b- 44 Figure 6.7b- 45 NAD + AT AD AT AD NAD + Energy investment phase Energy investment phase Energy harvest phase
Figure 6.7b- 46 Stage : Glycolysis 47 AT AD NAD + NAD + AT AD AD AT. Glycolysis uses two AT molecules per glucose to split the six-carbon glucose and makes four additional AT directly when enzymes transfer phosphate groups from fuel molecules to AD. Thus, glycolysis produces a net of two molecules of AT per glucose molecule. Energy investment phase Energy harvest phase Figure 6.8 48 Stage : The Citric Acid Cycle 49 Enzyme In the citric cycle, pyruvic from glycolysis is first groomed. AD AT Each pyruvic loses a carbon as CO. The remaining fuel molecule, with only two carbons left, is acetic. Oxidation of the fuel generates.
Stage : The Citric Acid Cycle 50 Figure 6.9 5 Finally, each acetic is attached to a molecule called coenzyme A to form acetyl CoA. The CoA escorts the acetic into the first reaction of the citric cycle. INUT (from glycolysis) Oxidation of the fuel generates NAD + OUTUT (to citric cycle) CoA The CoA is then stripped and recycled. yruvic yruvic loses a carbon as CO CO Acetic Coenzyme A Acetic attaches to coenzyme A Acetyl CoA Figure 6.9a 5 Figure 6.9b 5 INUT (from glycolysis) OUTUT (to citric cycle) NAD + Oxidation of the fuel generates OUTUT CoA yruvic Acetyl CoA yruvic loses a carbon as CO CO Acetic Coenzyme A Acetic attaches to coenzyme A
Stage : The Citric Acid Cycle 54 55 The citric cycle extracts the energy of sugar by breaking the acetic molecules all the way down to CO, uses some of this energy to make AT, and forms and FADH. Blast Animation: Harvesting Energy: Krebs Cycle Select lay Figure 6.0 INUT Citric OUTUT 56 Figure 6.0a INUT OUTUT 57 Acetic CO Acetic CO AD + NAD + FAD 6 Citric Acid Cycle Acceptor molecule AT FADH 4 5 AD + NAD + FAD AT FADH 4 5
Figure 6.0b INUT Citric OUTUT 58 Stage : Transport 59 transport releases the energy your cells need to make the most of their AT. The molecules of the electron transport chain are built into the inner membranes of mitochondria. Citric Acid Cycle Acceptor molecule 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. Stage : Transport 60 Figure 6. 6 When the hydrogen ions flow back through the membrane, they release energy. The hydrogen ions flow through AT synthase. AT synthase Space between membranes carrier rotein complex 5 takes the energy from this flow and Inner mitochondrial membrane synthesizes AT. flow FADH FAD O H O 6 4 NAD + AD AT Matrix transport chain AT synthase
Figure 6.a Space between membranes carrier rotein complex Inner mitochondrial membrane flow FADH NAD + FAD Matrix transport chain AT synthase O 4 H O AD 5 6 AT 6 Figure 6.b Space between membranes carrier rotein complex Inner mitochondrial membrane flow FADH NAD + FAD O 4 6 H Matrix transport chain Figure 6.c 64 Stage : Transport 65 + 5 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 AT. O H O 6 4 AD AT AT synthase
The Results of Cellular Respiration 66 Figure 6. 67 Cellular respiration can generate up to molecules of AT per molecule of glucose. Cytoplasm 6 FADH Mitochondrion Glycolysis Glucose yruvic Acetyl CoA Citric Acid Cycle Transport Maximum per glucose: AT AT About 8 AT About AT by direct synthesis by direct synthesis by AT synthase Figure 6.a 68 The Results of Cellular Respiration 69 Glycolysis Glucose yruvic Acetyl CoA Citric Acid Cycle Transport In addition to glucose, cellular respiration can burn diverse types of carbohydrates, fats, and AT AT About 8 AT proteins. by direct synthesis by direct synthesis by AT synthase
Figure 6. Food 70 FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY 7 olysaccharides Fats roteins Sugars Glycerol Fatty s Amino s Some of your cells can actually work for short periods without oxygen. Fermentation is the anaerobic (without oxygen) harvest of food energy. Glycolysis Acetyl CoA Citric Acid Cycle Transport AT Fermentation in Human Muscle Cells 7 Fermentation in Human Muscle Cells 7 After functioning anaerobically for about 5 seconds, muscle cells begin to generate AT by the process of fermentation. Fermentation relies on glycolysis to produce AT. Glycolysis does not require oxygen and yruvic, produced by glycolysis, is reduced by, producing NAD +, which keeps glycolysis going. In human muscle cells, lactic is a by-product. produces two AT molecules for each glucose broken down to pyruvic.
74 Figure 6.4 75 INUT AD AT OUTUT Glycolysis Glucose NAD + NAD + yruvic Lactic Animation: Fermentation Overview Right click slide / select lay The rocess of Science: What Causes Muscle Burn? 76 The rocess of Science: What Causes Muscle Burn? 77 Observation: Muscles produce lactic under anaerobic conditions. Question: Does the buildup of lactic cause muscle fatigue? Hypothesis: The buildup of lactic would cause muscle activity to stop. Experiment: Tested frog muscles under conditions when lactic could and could not diffuse away.
Figure 6.5 Battery + Force measured Battery + Force measured 78 The rocess of Science: What Causes Muscle Burn? Results: When lactic could diffuse away, performance improved greatly. 79 Frog muscle stimulated by electric current Conclusion: Lactic accumulation is the primary cause of failure in muscle tissue. However, recent evidence suggests that the role of lactic in muscle function remains unclear. Solution prevents diffusion of lactic Solution allows diffusion of lactic ; muscle can work for twice as long Fermentation in Microorganisms 80 Fermentation in Microorganisms 8 Fermentation alone is able to sustain many types of microorganisms. Yeast is a microscopic fungus that uses a different type of fermentation and The lactic produced by microbes using fermentation is used to produce produces CO and ethyl alcohol instead of lactic. cheese, sour cream, and yogurt, soy sauce, pickles, and olives, and sausage meat products. This type of fermentation, called alcoholic fermentation, is used to produce beer, wine, and breads.
Figure 6.6 8 Evolution Connection: Life before and after Oxygen 8 Glycolysis could be used by ancient bacteria to make AT INUT Glucose AD AT + Glycolysis NAD + yruvic CO released NAD + + OUTUT Ethyl alcohol 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. Figure 6.7 0 84 Billions of years ago...7.5 O present in Earth s atmosphere First eukaryotic organisms Atmospheric oxygen reaches 0% of modern levels Atmospheric oxygen first appears Oldest prokaryotic fossils 4.5 Origin of Earth