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Assessment Statements Cellular Respiration CORE 3.7.1 Define cell respiration. 3.7.2 State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. 3.7.3 Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. 3.7.4 Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP. Biology 11 A. Allen AHL 8.1.1 State that oxidation involves the loss of electrons from an element, whereas reduction involves a gain of electrons; and that oxidation frequently involves gaining oxygen or losing hydrogen, whereas reduction frequently involves losing oxygen or gaining hydrogen. 8.1.2 Outline the process of glycolysis, including phosphorylation, lysis, oxidation and ATP formation. 8.1.3 Draw and label a diagram showing the structure of a mitochondrion as seen in electron micrographs. 8.1.4 Explain aerobic respiration, including the link reaction, the Krebs cycle, the role of NADH + H+, the electron transport chain and the role of oxygen 8.1.5 Explain oxidative phosphorylation in terms of chemiosmosis. 8.1.6 Explain the relationship between the structure of the mitochondrion and its function. 1 2 http://fusionanomaly.net/mitochondria.html Activation Energy Cellular Respiration • Cellular respiration is… The process by which a cell breaks down sugar or other organic compounds to release energy used for cellular work; may be anaerobic or aerobic, depending on the availability of oxygen. Aerobic respiration can be summarized by the following formula: C6H12O6 + 6O2 6H20 + 6CO2 + energy (36 ATP) 3 4 An overview of Aerobic Cellular Respiration Glycolysis • Glycolysis is the first stage of cellular respiration. • Glycolysis has two parts; Glycolysis I & Glycolysis II. In order to ‘kick-start’ glycolysis I, activation energy is required (ATP). Sugar is split into two G3Ps. In glycolysis II, G3P is oxidized and ATP is produced. The overall pathway gets its name from this sugar splitting (glyco = sugar, lysis = split). • Glycolysis occurs in the cytosol (The fluid portion of the cytoplasm, outside the organelles ). Can you find Glycolysis? 5 6 1 Glucose 6-C Coenzyme Glycolysis I 1 • ATP ADP • A substance that enhances or is necessary for the action of enzymes. They are generally much smaller than enzymes themselves. NAD (Nicotinamide adenine dinucleotide) is a coenzyme that serves and an electron carrier. 1. Glucose enters the cell by diffusion 3 2. ATP donates a phosphate to the substrate. (1 ATP used) Glucose-6-phosphate is produced. Fructose~P “fructose-6-phosphate” 6-C, 1 Phosphate 3. Glucose-6-phosphate is rearranged to fructose-6-phosphate (another 6-C sugar) ATP 4 4. another ATP donates its phosphate (1 ATP used). Fructose 1,6-bisphosphate is produced. ADP P~ Fructose ~P “Fructose 1,6-bisphosphate” 6-C, 2 Phosphates X2 G3P AKA G3P G3P AKA G3P 5 (3-C, 1 phosphate) • Pi NADH is formed). The oxidized G3P then accepts a Pi from the cytosol. 1,3 bisphosphoglyerate (3-C, 2 phosphates) ADP (BPG) is formed ATP 2. ADP is phosphorylated to ATP (x2) as it removes the phosphate from the substrate. 3-phosphoglycerate is formed. (substrate level phosphorylation: when ADP removes Pi from the substrate to form ATP) 3-phosphoglycerate (3-C, 1 phosphate) X2 In Glycolysis II, each G3P (2 from 1 molecule of glucose) is oxidized to release energy. This process is exergonic. Substrate Level Phosphorylation 1. G3P is oxidized. NAD takes electrons (NADH 1,3 bisphosphoglycerate (BPG) 2 8 Glycolysis II G3P (3-C, 1 phosphate) 1 5. The fructose 1,6 bisphosphate molecule is split into 2 G3Ps (glyceraldehyde 3phosphate), a 3-carbon compound. Note G3P is also known as glyceraldehyde 3phosphate (G3P) **Glycolysis I …** •2 ATP (2 ATP’s are used.) Animation NAD+ Glycolysis I is a series of endergonic reactions Glucose ~P “glucose-6-phosphate” 6-C, 1 Phosphate DHAP 7 2 2-phosphoglycerate (3-C, 1 phosphate) • The direct phosphate transfer of phosphate from an organic molecule to ADP. 3. 3-phosphoglycerate is rearranged to 2- 3 phosphoglycerate which is then rearranged to phosphoenolpyruvate (PEP). Water is given off in this process. H2O phosphoenolpyruvate (PEP) ADP 4. PEP gives a phosphate to ADP to make ATP. Pyruvate (AKA Pyruvic acid) is formed. ATP 4 Pyruvate (Pyruvic Acid) (3-C, 0 phosphates) Animation **Glycolysis results in a net gain of …** •2 ATP (2 ATP’s are used and 4 are produced) 9 •2 NADH These hydrogens are transported to the mitochondria for more ATP production 10 Think Together! Vocabulary GAME! Partners `A` and `B` take turns answering the questions below. • • • • • • • • • A. What is the basic difference between Glycolysis I and Glycolysis II? B. What is the role of NAD? 11 Glucose fructose G3P Pyruvate phosphate Glucose-6 phosphate NADH ADP endergonic 12 2 • Decarboxylation-removal of a carboxyl group 13 Circle the end products of glycolysis. Where do they go next? 14 Pyruvate Oxidation (IB calls this the ‘Link Reaction’) Pyruvate (pyruvic acid) (3-C) + NAD NADH 1 CO2 Acetate (Acetic acid ) (2-C) 2 X2 Coenzyme A (or ‘CoA’) acetyl coenzyme A (or ‘acetyl coA’) 2. Animation Pyruvate Oxidation Remember, in glycolysis, glucose was oxidized to 2 pyruvate molecules. Therefore, the above biochemical pathways run twice for every molecule of glucose! Pyruvate Oxidation ONLY HAPPENS IF O2 is present! 1. The two pyruvate from glycolysis diffuse into the mitochondrion’s matrix. Here, it is oxidized by NAD+ (which is reduced to NADH NADH)) to make acetate,, a 2acetate 2-carbon compound. (The carbon is lost in the form of CO2) Acetic acid combines with coenzyme A to form acetyl coenzyme A. A. **Pyruvate Oxidation results in a net gain of …** •2 NADH. These hydrogens are transported to the Electron Transport Chain for more ATP production 15 16 Krebs Cycle 1. Animation acetyl coenzyme A (or ‘acetyl coA’) Coenzyme A (or ‘CoA’) 1 2. Oxaloacetate (4-C) 3. Citrate (6-C) 2 Isocitrate (6-C) X2 NAD 3 4. NADH CO2 α -ketoglutarate (5-C) Co Co--A CO2 Co Co--A Succinate 5 (4-C ) NAD Succinyl--CoA Succinyl (4-C ) GTP GDP + Pi NADH 4 5. Acetyl coenzyme A enters the Krebs cycle and combines with Oxaloacetate (4-C), to make citrate (6-C). Coenzyme A is recycled for further use. Citrate is rearranged to isocitrate (6-C) NAD accepts hydrogens from isocitrate which is therefore oxidized. One molecule of CO2 is given off as isocitrate loses one carbon. α-ketoglutarate (5-C) is formed. α -ketoglutarate (5-C) is oxidized to succinyl Co-A (4-C). A CO2 is removed, coenzyme A is added, and 2 hydrogen atoms reduced NAD to NADH. Succinyl C0-A is produced. Succinyl Co-A (4-C) is converted to succinate (4-C). A Pi from the matrix displaces C0-A from succilyl Co-A. The phosphate is then tansfered to GDP (guanosine diphosphate) to make GTP. Then the Pi is transferred to ADP to make ATP! ADP + Pi Can you find Pyruvate oxidation? Where does it occur? 17 ATP 18 3 Krebs Cycle 6. Animation acetyl coenzyme A (or ‘acetyl coA’) Coenzyme A (or ‘CoA’) 1 8 7. Oxaloacetate (4-C) Citrate (6-C) NADH 7 8. 2 NAD malate (4-C) Isocitrate (6-C) X2 H20 NAD 3 NADH CO2 fumarate (4-C) Succinate (4-C) is oxidized to fumarate (4-C). Not enough energy is released to reduce NAD, so FAD is instead reduced to FADH2. Fumarate (4-C) is converted to malate (4-C). Malate is oxidized to oxaloacetate (4-C). 2 hydrogens are reduced NAD to NADH. Oxaloacetate has been restored, so the cycle can continue! Yahoo! α ketoglutarate (5-C) 6 FADH2 FAD Co Co--A CO2 Co Co--A Succinate 5 (4-C ) NAD Succinyl--CoA Succinyl (4-C ) GTP GDP ADP + Pi 4 Only 2 ATP’s have been produced from Krebs cycle. NADH Final products of Krebs Cycle per molecule of glucose: 3 x 2 = 6 NADH (to electron transport chain to make ATP) ATP) 1 x 2 = 2 FADH2 (to electron transport chain to make ATP) ATP) 1 x 2 = 2 ATP 19 ATP 20 Think Together! • Why is there a “X2” on the diagram of the Krebs Cycle? • Krebs cycle only yields 2 ATP per molecule of glucose, but it also results in 6 NADH and 2 FADH2 produced. What do you think NADH and FADH2 is for? 22 21 Oxidative Phosphorylation (Electron Transport Chain) …Oxidative Phosphorylation (Electron Transport Chain) Animation #1 Animation #1 Animation #2 Animation #2 1 • The electron transport chain is located on the inner membrane of the mitochondrion. It consists of several electron carriers which accept electrons from NADH and FADH2 (from glycolysis and Krebs cycle). It requires O2! 23 2 [1] Energized electrons from Glycolysis and Krebs cycle are carried to the electron transport chain via NADH... [2] ...and FADH2 24 4 …Oxidative Phosphorylation (Electron Transport Chain) …Oxidative Phosphorylation (Electron Transport Chain) Cytochrome c oxidase complex (H+ pump) Cytochrome c oxidase complex (H+ pump) 3 3 4 Animation #1 4 Animation #1 Animation #2 Animation #2 7 NADH Dehydrogenase NADH Dehydrogenase 2 1 (H+ pump) 6 2 1 (H+ pump) 5 Cytochrome bc1 complex (H+ pump) Cytochrome bc1 complex (H+ pump) [3] Electrons are passed through a series of electron carriers which become reduced/oxidized as they pass off the electrons [complexes I -IV]. At different places along this chain, the energy released from the electrons is used to ‘pump’ protons (H+) across the inner membrane of the mitochondrion into the intermembrane space [4] This creates a concentration gradient in the intermembrane space. 25 [5] The H+ ions are allowed to pass back into the matrix through ATP synthase. [6] Using the energy from the flow of protons, ADP is united with Pi to form ATP. Note that because NADH and FADH2 enter the electron transport chain at different locations, they yield different amounts of ATP; NADH yields 3 ATP and FADH2 yields 2 ATP. [7] The electrons unite with protons (H+) and oxygen at the end of the ETC to form water. 26 If insufficient O2 is available in the cell, the ETC will not work! What happens then?...... Electron Transport and Chemiosmosis Electron Transport and Chemiosmosis Fig. 9.15 H+ Cyt C CoQ CoQ NAD+ NADH H+ NAD+ NADH H+ H+ H+ 27 Electron Transport and Chemiosmosis H+ H+ H+ 28 Electron Transport and Chemiosmosis Fig. 9.15 H+ Fig. 9.15 H+ oxidase complex Cyt C CoQ H+ NAD+ Cytochrome c oxidase complex Cyt C NADH H+ H+ Cytochrome c H+ CoQ H+ NADH 29 H+ NAD+ 2 H+ + ½ O2 Electron transport chain H20 30 chemiosmosis 5 Smokin’ Chemiosmosis & Electron Transport Animations Electron Transport and Chemiosmosis H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ • http://vcell.ndsu.nodak.edu/animations/atp gradient/movie.htm • http://vcell.ndsu.nodak.edu/animations/etc/ movie.htm H+ NADH H+ NAD+ 2 H+ + ½ O2 H20 ADP + P ATP 31 Can you see why FADH2 & NADH end in different ATP yields? 32 Cyanide Blocks the Electron Transport Chain • Cyanide is a poison that inhibits cytochrome oxidase activity. Why can cyanide cause death? 33 34 36 37 Summary of Aerobic Cellular Respiration 6 Structural Formula of ATP • Label the diagram 38 39 Net Energy Yield of Aerobic Respiration Anaerobic vs. Aerobic Respiration • NOTE: What happens after glycolysis depends on whether or not oxygen is present… ATPs NADHs FADH2s ATPs From ETC Total ATPs If O2 is absent…. Glycolysis A 2 B 2 C0 D4 E6 Pyruvate (Pyruvic Acid) (3-C) Pyruvic Acid Oxidation F0 G 2 H0 I6 J6 Total 2 K P4 L6 10 Q 2 M R2 22 N 32 S Pyruvate Goes to the Kreb’s cycle in the mitochondria (aerobic respiration) for complete oxidation. NADH X2 NAD+ Krebs Cycle If O2 is present…. 24 O lactate (lactic acid) fermentation Lactate (Lactic acid) (3-C) 36 T Lactic acid (animals) Once thought to make muscles fatigued after Strenuous exercise) 41 Think Together! This process is called … 42 Alcoholic Fermentation (in yeast) With your partner, discuss: • Does lactic acid fermentation yield any energy? • Assume the energy demands within a cell greatly exceeds the body’s ability to deliver oxygen. What is the point of pyruvic acid being converted to lactic acid? HINT: NAD is a limited commodity in the cell. • An anaerobic step that yeast use after glycolysis that breaks down pyruvate to ethanol (aka ethyl alcohol) and carbon dioxide. Pyruvate (Pyruvic Acid) (3-C) C02 Acetaldehyde (2-C) NADH X2 NAD+ Ethanol (the alcohol found in beer, wine, etc.) (2-C) 43 44 7 Alternate Pathways • • Protein Catabolism Carbohydrates are your body’s nutrient of choice. Proteins lipids and nucleic acids can also be used. • • • • 45 Proteins are made of different types of amino acids. The amino groups of amino acids are removed (deamination). What remains of the amino acids are then converted to various components of glycolysis or Krebs i.e. pyruvate, acetyl CoA, alpha ketoglutarate. You know the rest! 46 Lipid Catabolism • Triglycerides are made of glycerol and fatty acids. Your digestive system breaks triglycerides into these components. • Glycerol may be converted into glucose via gluconeogenesis or to DHAP (what’s next…?) • The fatty acids enter the matrix and undergo beta oxidation (acetyl groups are removed from the fatty acids and combine with CoA to form Acetyl CoA… 47 8