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PLANT SCIENCE 184 Cellular Respiration: Harvesting Chemical Energy PowerPoint® Lecture Slides for Essential Biology, Second Edition & Essential Biology with Physiology Neil Campbell, Jane Reece, and Eric Simon Presentation prepared by Chris C. Romero Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Bacteria are used to produce yogurt, sour cream, pepperoni, and cheese • Both carbon monoxide and cyanide kill by disrupting cellular respiration Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • All the energy in all the food you eat can be traced back to sunlight • If you exercise too hard, your muscles shut down from a lack of oxygen Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings BIOLOGY AND SOCIETY: FEELING THE “BURN” • When you exercise – Muscles need energy in order to perform work – Your cells use oxygen to release energy from the sugar glucose Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Aerobic metabolism – When enough oxygen reaches cells to support energy needs • Anaerobic metabolism – When the demand for oxygen outstrips the body’s ability to deliver it Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Anaerobic metabolism – Without enough oxygen, muscle cells break down glucose to produce lactic acid – Lactic acid is associated with the “burn” associated with heavy exercise – If too much lactic acid builds up, your muscles give out Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Physical conditioning allows your body to adapt to increased activity – The body can increase its ability to deliver oxygen to muscles • Long-distance runners wait until the final sprint to exceed their aerobic capacity Figure 6.1 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings ENERGY FLOW AND CHEMICAL CYCLING IN THE BIOSPHERE • Fuel molecules in food represent solar energy – Energy stored in food can be traced back to the sun • Animals depend on plants to convert solar energy to chemical energy – This chemical energy is in the form of sugars and other organic molecules Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Producers and Consumers • Photosynthesis – Light energy from the sun powers a chemical process that makes organic molecules – This process occurs in the leaves of terrestrial plants Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Autotrophs – “Self-feeders” – Plants and other organisms that make all their own organic matter from inorganic nutrients • Heterotrophs – “Other-feeders” – Humans and other animals that cannot make organic molecules from inorganic ones Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Producers – Biologists refer to plants and other autotrophs as the producers in an ecosystem • Consumers – Heterotrophs are consumers, because they eat plants or other animals Figure 6.2 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Chemical Cycling Between Photosynthesis and Cellular Respiration • The ingredients for photosynthesis are carbon dioxide and water – CO2 is obtained from the air by a plant’s leaves – H2O is obtained from the damp soil by a plant’s roots • Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules – Oxygen gas is a by-product of photosynthesis Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Both plants and animals perform cellular respiration – Cellular respiration is a chemical process that harvests energy from organic molecules – Cellular respiration occurs in mitochondria • The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Sunlight energy Ecosystem Photosynthesis (in chloroplasts) Carbon dioxide Glucose Oxygen Water Cellular respiration (in mitochondria) for cellular work Heat energy Figure 6.3 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY • Cellular respiration – The main way that chemical energy is harvested from food and converted to ATP – This is an aerobic process—it requires oxygen Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The Relationship Between Cellular Respiration and Breathing • Cellular respiration and breathing are closely related – Cellular respiration requires a cell to exchange gases with its surroundings – Breathing exchanges these gases between the blood and outside air Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Breathing Lungs Muscle cells Cellular respiration Figure 6.4 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The Overall Equation for Cellular Respiration • A common fuel molecule for cellular respiration is glucose – This is the overall equation for what happens to glucose during cellular respiration Glucose Oxygen Carbon dioxide Water Energy Unnumbered Figure 6.1 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The Role of Oxygen in Cellular Respiration • During cellular respiration, hydrogen and its bonding electrons change partners – Hydrogen and its electrons go from sugar to oxygen, forming water Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Redox Reactions • Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions – Redox reactions for short Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The loss of electrons during a redox reaction is called oxidation • The acceptance of electrons during a redox reaction is called reduction Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Oxidation [Glucose loses electrons (and hydrogens)] Glucose Oxygen Carbon dioxide Water Reduction [Oxygen gains electrons (and hydrogens)] Unnumbered Figure 6.2 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings •RS IS NECESSARY IN ALL LIVING CELLS. •PLANTS ARE WELL KNOWN FOR PS, BUT THEY MUST ALSO REPIRE IN ORDER TO SURVIVE. • PS - OCCURS ONLY IN PLANT CELLS CONTAINING CHLOROPHYLL DURING THE DAYLIGHT HOURS. •RS - OCCURS IN ALL OF A PLANT’S LIVING CELLS 24 -7. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings WHY IS RS NECESSARY? PLANTS NEED ENERGY TO PERFORM MANY ESSENTIAL FUNCTIONS OF LIFE: GROWTH, REPAIR, NUTRIENT MOVEMENT, REPRODUCTION, & NUTRIENT TRANSPORT. Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The *Metabolic Pathway of Cellular Respiration • Cellular respiration is an example of a metabolic pathway – A series of chemical reactions in cells –building or degradation process • All of the reactions involved in cellular respiration can be grouped into three main stages – Glycolysis – The Krebs cycle – Electron transport – * WHAT IS METABOLISM? Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings A Road Map for Cellular Respiration Cytosol Mitochondrion High-energy electrons carried mainly by NADH High-energy electrons carried by NADH Glycolysis Glucose 2 Pyruvic acid Krebs Cycle Electron Transport Figure 6.7 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Stage 1: Glycolysis • Glycolysis breaks a six-carbon glucose into two three-carbon molecules – These molecules then donate high energy electrons to NAD+, forming NADH • A molecule of glucose is split into two molecules of pyruvic acid Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings 2 Pyruvic acid Glucose Figure 6.8 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Krebs Cycle Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Stage 2: The Krebs Cycle • The Krebs cycle completes the breakdown of sugar Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • In the Krebs cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl-CoA CoA 2 Acetic acid 1 Pyruvic acid CO2 3 Acetyl-CoA (acetyl-coenzyme A) Coenzyme A Figure 6.10 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The Krebs cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2 – The cycle uses some of this energy to make ATP – The cycle also forms NADH and FADH2 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Input Output 2 1 Acetic acid 2 CO2 ADP 3 Krebs Cycle 3 NAD 4 FAD 5 6 Figure 6.11 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Stage 3: Electron Transport • Electron transport releases the energy your cells need to make the most of their ATP Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The molecules of electron transport chains 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 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Protein complex Electron carrier Inner mitochondrial membrane Electron flow Electron transport chain ATP synthase Figure 6.12 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings The Versatility of Cellular Respiration • Cellular respiration can “burn” other kinds of molecules besides glucose – Diverse types of carbohydrates – Fats – Proteins Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Food Polysaccharides Sugars Glycerol Fats Fatty acids Proteins Amino acids Amino groups Glycolysis AcetylCoA Krebs Cycle Electron Transport Figure 6.13 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Adding Up the ATP from Cellular Respiration Cytosol Mitochondrion Glycolysis Glucose 2 Pyruvic acid 2 AcetylCoA Krebs Cycle Electron Transport Maximum per glucose: by direct synthesis by direct synthesis by ATP synthase Figure 6.14 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY • Some of your cells can actually work for short periods without oxygen – For example, muscle cells can produce ATP under anaerobic conditions • Fermentation – The anaerobic harvest of food energy Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation in Human Muscle Cells • Human muscle cells can make ATP with and without oxygen – They have enough ATP to support activities such as quick sprinting for about 5 seconds – A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds – To keep running, your muscles must generate ATP by the anaerobic process of fermentation Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • Glycolysis is the metabolic pathway that provides ATP during fermentation – Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going – In human muscle cells, lactic acid is a by-product Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings 2 ADP+ 2 Glycolysis 2 NAD 2 NAD Glucose 2 Pyruvic acid + 2 H 2 Lactic acid (a) Lactic acid fermentation Figure 6.15a Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation in Microorganisms • Various types of microorganisms perform fermentation – Yeast cells carry out a slightly different type of fermentation pathway – This pathway produces CO2 and ethyl alcohol Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings 2 ADP+ 2 2 CO2 released 2 ATP Glycolysis 2 NAD 2 NAD Glucose 2 Pyruvic acid + 2 H 2 Ethyl alcohol (b) Alcoholic fermentation Figure 6.15b Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The food industry uses yeast to produce various food products Figure 6.16 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings EVOLUTION CONNECTION: LIFE ON AN ANAEROBIC EARTH • Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere – Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings SUMMARY OF KEY CONCEPTS • Chemical Cycling Between Photosynthesis and Cellular Respiration Heat Sunlight Photosynthesis Cellular respiration Visual Summary 6.1 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The Overall Equation for Cellular Respiration Oxidation: Glucose loses electrons (and hydrogens) Glucose Carbon dioxide Electrons (and hydrogens) Oxygen Energy Reduction: Oxygen gains electrons (and hydrogens) Visual Summary 6.2 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings • The Metabolic Pathway of Cellular Respiration Glucose Oxygen Water Energy Visual Summary 6.3 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings