Aerobic Cellular respiration

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Aerobic Cellular respiration. Sbi4u by Sara Avent. agenda. Overview Lab investigations Redox reactions and free energy Glycolysis Pyruvate Oxidation The Krebs Cycle Electron Transport and Chemiosmosis Oxidative ATP Synthesis Energy efficiency. Curriculum expectations. - PowerPoint PPT Presentation

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Sbi4uby Sara AventAerobic Cellular respiration1agendaOverviewLab investigationsRedox reactions and free energyGlycolysisPyruvate OxidationThe Krebs CycleElectron Transport and ChemiosmosisOxidative ATP SynthesisEnergy efficiency

2Curriculum expectationsOverall ExpectationsC2. investigate the products of metabolic processes such as cellular respiration and photosynthesis;C3. demonstrate an understanding of the chemical changes and energy conversions that occur in metabolic processes.

Specific ExpectationsC2.1: use appropriate terminology related to metabolism, including, but not limited to: energy carriers, glycolysis, Krebs cycle, electron transport chain, ATP synthase, oxidative phosphorylation, chemiosmosis, proton pump.C2.2: conduct a laboratory investigation into the process of cellular respiration to identify the products of the process, interpret the qualitative observations, and display them in an appropriate format.

3C3.1: explain the chemical changes and energy conversions associated with the processes of aerobic and anaerobic cellular respiration (e.g., in aerobic cellular respiration, glucose and oxygen react to produce carbon dioxide, water, and energy in the form of heat and ATP).

C3.4: describe, compare, and illustrate (e.g., using flow charts) the matter and energy transformations that occur during the processes of cellular respiration (aerobic and anaerobic) and photosynthesis, including the roles of oxygen and organelles such as mitochondria and chloroplasts.

Curriculum expectations (Contd)Investigation

Using Pasco CO2 gas sensor students can observe real-time evidence germinating seeds are engaged in cellular respiration.

CO2 gas increases inside the flask with germinating seeds proof that cellular respiration is occurring as the seeds germinate.CO2 results from Pasco Probeware5Aerobic cellular respiration overviewAll organisms (except chemoautotrophs) use glucose as a primary source of energy.Through a series of enzyme-controlled redox reactions, the bonds are broken, and the molecule is rearranged into more stable configurations, and energy is released.C6H12O6 (aq) + 6O2(g) 6CO2 (g) + 6H2O (l) + heat + ATPoxidizedreducedchemoautotrophs: build all organic compounds needed for life without using light energy found in extreme environments like volcanoes, salt flats, etc.The more stable the covalent bonds are, the more free energy will be released.This reaction is a combustion reaction. All combustion reactions are redox reactions in which oxygen is the oxidizing agent, and all are exergonic reactions that release free energy.Redox reaction: electrons are transferred from glucose to oxygen.Glucose is oxidized to CO2 and oxygen is reduced to water (gaining e-).LEO says GER6Redox Reactions and energyC6H12O6 (aq) + 6O2(g) 6CO2 (g) + 6H2O (l) + heat + ATPCHOH

More orderedLess orderedIs this oxidation or reduction?Glucose has C-H bonds. Non-polar (0.4). Electron pairs sit in the middle between the two nuclei.12H from glucose break away and attaching to 6O from oxygen 6H2O. Is this oxidation or reduction, why? Hydrogen atoms are carrying electrons away from glucose = oxidation. O-H bonds have formed. O is extremely electronegative. The electrons are close to nucleus. They lose potential energy (less ordered state when close to a nucleus). This causes decrease in free energy and overall exergonic reaction. (releases energy)

7What about the rest?C6H12O6 (aq) + 6O2(g) 6CO2 (g) + 6H2O (l) + heat + ATP

OOOCMore orderedLess orderedRelease of Free Energy!Is this oxidation or reduction?The remaining O attaches to C CO2. Is this oxidation or reduction? Oxidation Why? [electronegative O atoms draw the electron pairs toward them carbon is essentially losing electrons].This places the electrons in a more stable configuration. Unstable stable = release of free energy.

8Visualising energyhttp://www.youtube.com/watch?v=6YWGnfnEmgM

26kJ9Redox reactions and Nicotinamide Adenine Dinucleotide

NAD+ removes 2H atoms (2 protons, 2 e-) from the glucose molecule. 2 e- and one proton attach to the NAD+, reducing it to NADH and the remaining proton dissolves in to the surrounding solution as H+ (aq).3. This is done by dehydrogenase enzyme.4. NAD+ is the oxidized form and NADH + H+ (shortened to NADH) is the reduced form. This occurs in stage 1, 2 and 3.FAD is reduced by 2 H atoms from the glucose molecule. It is reduced to FADH2 (because all protons and e- of H bind directly to the molecule). This occurs in Krebs cycle.7. These reductions are a way to harvest energy and transfer free energy to ATP.10Energy TransferThe ultimate goal of cellular respiration is to capture as much of the available free energy in the form of ATP. Substrate-level phosphorylation:

Substrate-level phosphorylation forms ATP using an enzyme catalyzed reaction.A phosphate containing compound transfers a phosphate group to ADP to form ATP In this case this is the final step of glycolysis in which pyruvate is formed by transferring its phosphate group to ADP.31kJ/mol of potential energy is transferred.This is how ATP is formed during glycolysis and the Krebs cycle.11How much energy is released?G = -2870 kJ/mol glucoseWhen glucose is burned in a test tube CO2, H2O are formed and heat and light are given off.Cells have evolved methods to trap this energy (ATP) to power endergonic processes in cell.

Overall decrease in potential energy increase in entropy a downhill process that provides 2870 kJ of free energy for every mole of glucose. (one mole = 180g)12In a living cell things get complicatedOxygen wont just bump into glucose and react in the environment.What would happen if it could?Solution: activation energy How does a cell control this process?Enzymes catalyze and control.

Convert glucose to CO2, H2O and energy very quickly. Life could not exist with so much oxygen in the air.Activation energy can prevent spontaneous combustion and control oxidation process.Glucose combustion needs a large amount of activation energy - like a flame used to burn glucose in a test tube.Cell uses a series of reactions with small activation energies.13Cellular Respiration Process

Stage 1Stage 4Stage 2Stage 3glycolysis: 10 step process in the cytoplasm of the cell.Pyruvate oxidation one step in the mitochondrial matrix.Krebs cycle/citric acid cycle/TCA cycle 8 steps in matrix.Electron transport and chemiosmosis (oxidative phosphorylation) multistep in inner mitochondrial membrane.14Stage 1: Glycolysis6-carbon glucose two 3-carbon pyruvatesGlyco = sugar; lysis = splitCytoplasm

10 reactions each step catalyzed by a specific enzyme.15

This is a complicated process, but dont worry students only need to identify and understand the important parts.So whats important?The points in the pathway where things are made or used.16

2 ATP are used in step 1 and 3.Phosphate groups are added to the glucose moleculeIn step 4 & 5 the molecule is split into DHAP and G3P. An enzyme converts DHAP to G3P. This produces two molecules of G3P.Step 6 produces two NADH (one from each G3P).Use 2ATP to add phosphate groups to glucose molecule. These phosphates are added so later they can be removed and energy is harvested.Molecule split into DHAP and G3P, DHAP converted to G3P.Step 6: NAD+ takes hydrogen atoms and reduces to NADH.17

In step 7, two ATP molecules are produced by substrate-level phosphorylation.The ATP debt is paid.In step 10, two ATP molecules are produced by substrate-level phosphorylation and pyruvate is formed.Step 7: 2 ATP are formed by phosphorylation of ADP. The phosphate group is transferred to ADP.Some rearranging occurs.Step 10: 2 ATP formed in the same way.18Energy yield for glycolysis4 ATP produced2 ATP used2 ATP produced net 2 NADH produced2 mol ATP x 31 kJ/mol ATP = 62 kJTotal free energy in 1 mol of glucose = 2870 kJEnergy conversion efficiency = 62 kJ x 100% = 2.2%2870 kJGlycolysis alone is not very energy harnessing.The energy is trapped in 2 pyruvate and 2 NADH.Gly OK for small microorganismsHumans need more aerobic respiration which occurs in the mitochondria and needs oxygen.19Stage 2: Pyruvate oxidationTwo pyruvate molecules are transported through the mitochondrial membrane into the matrix and acetyl-CoA is formed.

Overview20Pyruvate Oxidation

Carboxyl group is removed as CO2.The remaining two-carbon portion is oxidized by NAD+ and forms an acetyl group.Coenzyme A attaches to the acetyl and forms acetyl-CoA.

Enzyme catalyzed reaction (decarboxylation removing carboxyl group) pyruvate decarboxylase.NAD+ gains two H atoms (2 protons 2 electrons). Pyruvate is oxidized, NAD+ is reduced.The C-S bond that attaches the CoA to the acetyl group is unstable has high potential energy. This prepares the acetyl for further oxidation.Acetyl-CoA is a multifunction compound most lipids, carbohydrates and proteins are converted into acetyl-CoA if the body needs energy Krebs, if it doesnt stores energy as fat.21Products of pyruvate oxidation2 pyruvate + 2NAD+ + 2CoA 2acetyl-CoA + 2NADH + 2H+ + 2CO22 acetyl-CoA enter the Krebs cycle (stage 3).2 NADH go to the electron transport chain (stage 4) and produce ATP.2 CO2 diffuse out of the mitochondrion and out of cell (waste product).2 H+ remain dissolved in matrix.

22Stage 3: The Krebs CycleDiscovered in 1937 by Sir Hans Krebs.In 1953, Krebs and Fritz Albert Lipmann shared the Nobel Prize for their discoveries.Krebs cycle is a cyclic series of reactions that transfers energy from organic molecules to ATP, NADH, FADH2 and removes carbon atoms as CO2.

Retrieved from: http://www.nndb.com/people/619/000129232/Lipmann discovered coenzyme A.23

Two molecules of acetyl-CoA form for every molecule of glucose: the Krebs Cycle occurs twice for each molecule of glucos

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