Presentation on theme: "Objectives Contrast the roles of glycolysis and aerobic respiration in cellular respiration. Relate aerobic respiration to the structure of a mitochondrion."— Presentation transcript:
1 ObjectivesContrast the roles of glycolysis and aerobic respiration in cellular respiration.Relate aerobic respiration to the structure of a mitochondrion.Summarize the events of the Krebs cycle.Summarize the events of the electron transport chain and H+/ ATP synthase pump.Calculate the efficiency of aerobic respiration.
2 Photosynthesis Cell Respiration Cycle Light energyECOSYSTEMCO2 + H2OPhotosynthesis in chloroplastsCellular respiration in mitochondriaOrganic molecules+ O2ATPpowers most cellular workHeat energy
3 Life Is Work Living cells Require transfusions of energy (a.k.a., food) from outside sources to perform their many tasksThe giant panda obtains energy for its cells by eating plants
4 Harvesting Chemical Energy Cellular respiration is the process by which cells break down organic compounds to produce ATP.Both autotrophs and heterotrophs use cellular respiration to make CO2 and water from organic compounds and O2.The products of cellular respiration are the reactants in photosynthesis; conversely, the products of photosynthesis are reactants in cellular respiration.Cellular respiration can be divided into two stages: glycolysis and aerobic respiration.
5 Oxidative phosphorylation: electron transport and chemiosmosis An overview of cellular respiration…Electronscarriedvia NADHGlycolsisGlucosePyruvateATPSubstrate-levelphosphorylationElectrons carriedvia NADH andFADH2Citric acid cycleOxidative phosphorylation: electron transport and chemiosmosisOxidativeMitochondrionCytosolAEROBIC RESPIRATION
7 CELLULAR RESPIRATION (Figure 5.4, p. 133) ALL organisms do respiration!!!energy in glucose released to produce ATPtwo types of respirationAEROBIC (requires oxygen)ANAEROBIC (does not require oxygen)both types start with glycolysis
8 GLYCOLYSIS (Figure 5.6, p. 135)glycolysis is the first step of respirationoccurs in ALL cells!!!occurs in cytoplasm and is anaerobic (no O2)glucose is converted to pyruvic acidproduces 2 ATP (~2% of energy in 1 glucose)pyruvic acid then used in…fermentation oraerobic respiration
10 FERMENTATION (ANAEROBIC) occurs in cytoplasmconsumes pyruvic acid with no ATP production!!!LACTIC ACID FERMENTATION – creates lactic acidexample overworked muscles with low O2feels like cramp or sorenessALCOHOLIC FERMENTATION - produces ethyl alcohol and CO2used to make beer; wine; dough
11 (a) Alcohol fermentation (b) Lactic acid fermentation In alcohol fermentationPyruvate is converted to ethanol in two steps, one of which releases CO2During lactic acid fermentationPyruvate is reduced directly to NADH to form lactate as a waste product2 ADP + 2P12 ATPGlycolysisGlucose2 NAD+2 NADH2 Pyruvate2 Acetaldehyde2 Ethanol(a) Alcohol fermentation2 Lactate(b) Lactic acid fermentationHOHCH3CO –OO–CO22
12 Overview of Aerobic Respiration In eukaryotic cells, the processes of aerobic respiration occur in the mitochondria. Aerobic respiration only occurs if oxygen is present in the cell.The Krebs cycle occurs in the mitochondrial matrix. The electron transport chain (which is associated with the production of ATPs) is located in the inner membrane.
13 Mitochondria, the super-energy harvesters are the sites of aerobic cellular respirationare found in nearly all eukaryotic cellsare enclosed by two membranessmooth outer membranean inner membrane folded into cristae (i.e., higher surface area for chemical reactions)
15 AEROBIC RESPIRATION (requires O2) Net reaction…mitochondriaC6H12O6 + 6O CO2 + 6H2O + ATPenzymes
16 The Krebs CycleIn the mitochondrial matrix, pyruvic acid produced in glycolysis reacts with coenzyme A to form acetyl CoA. Then, acetyl CoA enters the Krebs cycle.One glucose molecule is completely broken down in two turns of the Krebs cycle. These two turns produce four CO2 molecules, two ATP molecules, and hydrogen atoms* that are used to make six NADH* and two FADH2* molecules.* The energy released by the breakdown of glucose is about to be transferred to ATP!!!
18 AEROBIC RESPIRATION (requires O2) occurs ONLY in mitochondria (Figure 5.10, p.138)pyruvic acid from glycolysis is metabolized in the KREB’S CYCLEoccurs in the matrixtwo turns of cycle (1 glucose molecule) yields 4 CO2, 2 ATP, and several energy rich molecules (NADH and FADH2 )the energy rich molecules NADH and FADH2 are used to make a lot of ATP energy rich (using electron transport chains and ATP synthase)
20 Enzymes in the Kreb’s (or citric acid) cycle… pyruvate
21 Summary of Kreb’s (Citric Acid) Cycle X 2diffuse outX 2used in e- transport chainX 2X 2used in e- transport chainX 2
22 Electron Transport Chain and ATP Synthesis High-energy electrons from from NADH and FADH2 are passed from molecule to molecule in the electron transport chain along the inner mitochondrial membrane.Hydrogen ions, H+, are also given up by NADH and FADH2.As the electrons move through the electron transport chain, they lose energy. This energy is used to pump protons from the matrix into the intermembrane space.The resulting concentration gradient of hydrogen ions drives ATP synthase and ATP production!
23 Electron Transport Chain, H+, & ATP synthesis H+ move through ATP synthase to make ATP from ADP+PiOxygen combines with the electrons and protons to form water.
24 Electron Transport Chain and ATP synthase The Importance of OxygenATP can be synthesized using the diffusion of H+ ions from the outer compartment to the inner compartment only if electrons continue to move along the electron transport chain.Oxygen is the final electron acceptorAs a result, ATP can continue to be made through the ATP pump.
28 AEROBIC RESPIRATION Electron Transport Chains & ATP synthesis uses membrane bound proteinsO2 molecules are consumedthis produces 32 more ATPSO... total yield of ATP (1 glucose molecule) from aerobic respiration AND glycolysis = 38 ATP19-times more ATP than from anaerobic respiration alone !!! (~40% of the energy in a glucose molecule is converted to ATP)WHAT HAPPENS TO THE OTHER 60%?
30 Another Role of Cellular Respiration A Summary of Cellular RespirationAnother Role of Cellular RespirationProviding cells with ATP is not the only important function of cellular respiration.Molecules formed at different steps in glycolysis and the Krebs cycle are often used by cells to make compounds that are missing in food.fatty acids, glycerol, amino acids
32 Fermentation consists of (REVIEW) GlycolysisCan produce ATP with or without oxygen, in aerobic or anaerobic conditionsGlycolysis is often coupled with fermentation to produce a few more ATP, especially in prokaryotesFermentation consists ofGlycolysis plus either alcohol or lactic acid fermentation
33 Fermentation and Cellular Respiration Compared Both fermentation and cellular respirationUse glycolysis to oxidize glucose and other organic fuels to pyruvateCellular respiration (i.e., complete oxidation) is more efficient than anaerobic respiration pathwaysProduces more 19x more ATP (38 versus 2 ATP)
34 Pyruvate is a key juncture in catabolism GlucoseCYTOSOLPyruvateNo O2 presentFermentationO2 presentCellular respirationEthanolorlactateAcetyl CoAMITOCHONDRIONCitricacidcycle
35 The Evolutionary Significance of Glycolysis Occurs in nearly all organismsProbably evolved in ancient prokaryotes before there was oxygen in the atmosphereThe pathways are similar (or conserved) across nearly all kingdoms (i.e., they are physiologically important and have not changed very much)