Chapter 7Cellular RespirationSection 7-1: Glycolysis and FermentationHarvesting Chemical Energy:All organisms require the energy stored in carbohydrates.Section 7-1: Glycolysis and FermentationHarvesting Chemical Energy:Cellular respiration: the process of breaking down carbohydrates into ATP (energy).Cellular respiration begins with a biochemical pathway called glycolysis.Section 7-1: Glycolysis and FermentationGlycolysis:Glycolysis: the beginning steps of cellular respiration.Spends 2 ATP and releases 4 ATP. After glycolysis, cellular respiration can follow either of two biochemical pathways:Fermentation (anaerobic respiration).Aerobic respiration.Section 7-1: Glycolysis and FermentationAerobic vs. Anaerobic Respiration:Aerobic respiration: the process of converting carbohydrates into ATP in the presence of oxygen.Lots of ATP.Anaerobic respiration: the process of converting carbohydrates into ATP in the absence of oxygen.Small amounts of ATP.Section 7-1: Glycolysis and FermentationGlycolysis:Glucose: a simple sugar.Glycolysis: a process in which glucose is changed to pyruvic acid and ATP.Glycolysis requires the input of two molecules of ATP.Steps of GlycolysisTwo phosphate groups supplied by two molecules of ATP are attached to the glucose. This forms a new six-carbon molecule.The new six-carbon molecule then splits into two three-carbon molecules called PGAL.Steps of GlycolysisSteps of GlycolysisEach molecule of PGAL gains another phosphate group changing the substance into another three-carbon molecule. Steps of Glycolysis4.The phosphate groups added in steps 1 and 3 are removed, which leaves you with 2 molecules of pyruvic acid. Each of the four phosphate groups that was removed is attached to its own ADP molecule, forming ATP. Thus, resulting in four molecules of ATP being formed.Steps of GlycolysisSection 7-1: Glycolysis and FermentationOutcome of Glycolysis:4 molecules of ATP.Net yield of 2 molecules of ATP (input of 2 ATP).Formation of 2 molecules of pyruvic acid.Well, what happens to the pyruvic acid?Section 7-1: Glycolysis and FermentationFermentation:If no oxygen is present, then the pathway is called fermentation.As a result of fermentation, either lactic acid or ethyl alcohol is produced.Section 7-1: Glycolysis and FermentationLactic Acid Fermentation:No more ATP molecules are formed as a result of lactic acid fermentation.Process of converting pyruvic acid to lactic acid.The resulting energy output of glycolysis and lactic acid fermentation is 2 ATP.Section 7-1: Glycolysis and FermentationSteps of GlycolysisSection 7-1: Glycolysis and FermentationLactic Acid Fermentation:Production of yogurt and cheese.Lactic acid fermentation also takes place in your muscle cells during physical activities.The reason that your muscles feel sore.Muscle cells use up all of the local oxygen and thus need to switch to lactic acid fermentation.This causes muscle cells to become unable to continually contract.Section 7-1: Glycolysis and FermentationAlcoholic Fermentation:Used in some plant cells and other unicellular organisms, such as yeast.The result of alcoholic fermentation is that pyruvic acid is converted to ethyl alcohol and CO2.Steps of GlycolysisSection 7-1: Glycolysis and FermentationAlcoholic Fermentation:The basis for the beer and wine industry:Yeast is added to a mixture to produce ethyl alcohol.Also used in the baking industry:Yeast is added to a mixture, which causes CO2 to be produced. The CO2 makes the bread rise.Section 7-2: Aerobic RespirationOverview of Aerobic Respiration:There are two major steps in aerobic respiration:The Krebs Cycle.The Electron Transport Chain.Section 7-2: Aerobic RespirationOverview of Aerobic Respiration:In prokaryotes, aerobic respiration takes place in the cytoplasm of the cell.In eukaryotes, these biochemical pathways occur inside the mitochondria.Section 7-2: Aerobic RespirationOverview of Aerobic Respiration:When pyruvic acid (from glycolysis) enters the cells mitochondria, it reacts with an enzyme called coenzyme A to form acetyl CoA.What does an enzyme do?Section 7-2: Aerobic RespirationThe Krebs Cycle:Krebs cycle: a biochemical pathway that breaks down acetyl CoA to produce CO2, and 2 more ATP.Note the word cycle.There are 5 steps to the Krebs cycle, which all occur in the mitochondria.The Krebs CycleA 2-carbon molecule of acetyl CoA combines with a 4-carbon molecule called oxaloacetic acid to form a 6-carbon molecule called citric acid.Citric acid releases CO2 and a hydrogen atom to form a 5-carbon molecule.The Krebs CycleThe 5-carbon molecule also releases CO2 and a hydrogen atom to form a 4-carbon molecule. In this step, ATP is formed from ADP.The 4-carbon molecule releases another hydrogen to form a new 4-carbon molecule. The Krebs CycleThe new 4-carbon molecule loses another hydrogen molecule. The Krebs CycleSection 7-2: Aerobic RespirationThe Krebs Cycle:For every molecule of glucose, there is 2 ATP and 4 CO2 molecules formed during the Krebs cycle.Two turns of the Krebs Cycle for every glucose molecule.How many molecules of ATP are formed after glycolysis and the Krebs cycle?4 ATP.Section 7-2: Aerobic RespirationThe Electron Transport Chain:Electron Transport Chain: the second stage of aerobic respiration.In eukaryotic cells:Occurs in the folds of the inner membranes of the mitochondria. In prokaryotic cells:Occurs in the cell membrane.Section 7-2: Aerobic RespirationThe Electron Transport Chain:The result of the electron transport chain is 34 ATP. Section 7-2: Aerobic RespirationSummarizing Cellular Respiration:The overall chemical equation for aerobic respiration is:C6H12O6 + 6O2 6CO2 + 6H2O + energySection 7-2: Aerobic RespirationSummarizing Cellular Respiration:The final result of aerobic respiration is 38 ATP (2 from glycolysis, 2 from the Krebs cycle, and 34 from the electron transport chain) vs. 2 ATP for anaerobic respiration.