Chapter 24- Glycolysis, Krebs Cycle & Electron Transport Chain
Chapter 24- Glycolysis, Krebs Cycle & Electron Transport Chain KNR 182
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Date Created: 09/28/15
HUMAN ANATOMY amp PHYSIOLOGY KNR 182 Glycolysis Krebs Cycle amp ETC Chapter 24 Carbohydrate Metabolism Oxidation of glucose C36H12C6 602 9 6H20 6002 38 ATP heat Glucose is catabolized in three pathways Glycolysis Occurs in the cytosol Krebs cycle Occurs in the mitochondria Electron transport chain and oxidative phosphorylation Occurs in the mitochondria Glycolysis Carbohydrates are prepared for the Kreb39s cycle through a process known as glycolysis A catabolic pathway that begins with glucose 6 carbon atoms per molecule ends with pyruvic acids 3 carbons atoms per molecule 1 glucose 2 pyruvic acids Glycolysis 10step pathway with 3 main stages Anaerobic or Aerobic Doesn t use 02 for the Numeoi s x V Glycosomes V i n 5 a Smooth endoplasmic f L H7 reticulum I 39 I N i I quotI 2 quotg t Cytosol mt VJ Equot w I q Lysosome Mitochondrion Centnoles Centres m matrix 439quot H quot llyl 7 f l I I 5 g I I gv b 39 39 u Microv li Microiilament I 39 quotquot jiy39 Secreuonbeing released v 1 I 5 1 v39 V r from cell by exocytosls I V Intermediate w 39 szw 39 u 39 I away laments Peroxisome Copying a 2001 Benjamin Cummings an imprint ol Addison Wesley Longman inc Microtmuie 3 phases regardless if 02 is present or not However the fate of the ATP yield is dependent on 02 Glycolysis is considered both anaerobic amp aerobic Occurs in the cytosol of the cell Cytosol contains the enzymes necessary to catalyze each of the chemical reactions that make up the glycolytic pathway Glycolysis Three major phases 1 Sugar activation Glucose is phosphorylated by 2 ATP to form fructose1 6biphosphate Energy investment state have to use ATP in order for glycolysis to occur 2 Sugar cleavage fructose 3 Sugar oxidation and ATP formation 3 carbon sugars are oxidized reducing NAD Inorganic phosphate groups Pi are attached to each oxidized fragment 4 ATP are formed by substratelevel phosphorylation DIRECT ATP SYNTHESIS NAD that is recuced picks up H 9 NADH2 Need to know initial substrates and final products Phases of Glycolysis 1 Sugar activation Glucose is phosphorylated by 2 ATP to form fructose1 6bisphosphate Energy Investment Stage Phases of Glycolysis 2 Sugar cleavage Fructose16bisphosphate is split into 3Carbon sugars Dihydroxyacetone phosphate Glyceraldehyde 3phosphate Glycolysis For each glucose molecule that enters glycolysis the final products are 2 pyruvic acid Converted to lactic acid if 02 not readily available Enter aerobic pathways if 02 is readily available 2 NADH2 reduced NAD 4 ATP Created 2 ATP used in sugar activation stage so net gain is only 2 ATP When we don t have oxygen present we get lactic acid Glycolysis final products Two pyruvic acid molecules can follow two distinct pathways Depending on the availability of oxygen 1 Adequate 02 NADH2 delivers hydrogen atoms to Electron Transport Chain Enters aerobic pathways if oxygen is readily available 2 NADH2 2 Inadequate 02 NADH2 unloads back onto pyruvic acid lactic acid This is why glycolysis is considered both anaerobic and aerobic Every chemical reaction is reversible except for when it gets to the Glucose 6Phosphate AEROBIC GLYCOLYSIS Glluccsc l xPhccphate lluccsc Ed Energy Summary P 3 phccphcglyccric Acid E7quot 2 phccphcglyccric Acid Ea Phcsphccnclxxp uvic Acid 2 phccphcglyccric Acid 54 Phcsphccnclmpymvic Acid Fructose l 6diphcsphade Fructose 6Phccphcte llycci39aldch ydc 3xiphcsphate E llycci39aldhydc Bxphosphate 13 Diphccphcglyccric Acid JL 3 phccphcglyccric Acid 13 Diphccphcglyccric Acid MIcchondi39ia Aerobic Mctabclism su Ticicnt mitochcnldril activity Acctyl 00A 1r KREBquotS CYCLE amp ETC Acctyl 739 00A Anaerobic Metabolism Aerobic glycolysis 02 present Produces large quantities of energy Anaerobic glycolysis Not enough 02 Produces lactate 2 ATP Lactate causes muscle cramps but it is not a debt of energy Not dead energy 02 reenters system 9 lactate 9 pyruvate 9 Krebs metabolic pathways ATP M New GLYCOLYSIS ATP Phosphatc i T J H i JU Hiiisumii UUJ Hm Hii ii l 4 Mimi i Phdsphccillpymvic Acid ATP chtcsc Phosphatc 1 mphpmte chtcsc 13 mph1111031me Acid TP phosphgiyccric Acid K k ATP Ph sph lljp3 39il fi Acid r phvosphgiyccric Acid Glycmaldchydc 3phphatc gphphatc Glycmalvt lytic 13 Diphthog lw ric Acid ATP NADH j kj Anacr hic Mctahnlismn insu cicnt mitochan activity 7 Lactate 1r Lactate Check your comprehension The final product of glycolysis from one molecule of glucose yields 2 ATP Krebs Cycle Occurs in mitochondrial matrix Macronutrients are converted into Acetyl CoA initial substrate Double membrane in the mitochondria The Krebs Cycle is fueled by Acetyl CoA Glucose 9 Pyruvic Acid 9 Acetyl CoA M Triglycerides 9 Fatty Acids 9 Acetyl CoA Proteins Protein 9 Amino Acids 9 Acetyl CoA The Acetyl CoA is catabolized oxidized and decarboxylated Krebs Cycle Transitional phase Each pyruvic acid is converted to acetyl CoA 1 Decarboxylation removal of 1 carbon to produce acetic acid and 002 Carbon atoms are removed one by one CO2 is produced by cellular respiration This is the first time that C02 is produced Its not produced in glycolysis 2 Oxidation H is removed from acetic acid and picked up by NAD 1 NADH2 produced for each pyruvic acid converted to acetyl CoA in transitional phase NAD is reduced to NADH2 3 Acetic acid coenzyme A forms acetyl CoA Transitional phase produces 002 and NADH Acid gtEH Citric Acid E2 c Amnitic Acid CHAIN Inner CMitnzcEImml al Membrane V Immu Cumpartmeni mifuochondial matrix Summit Acid an Ketoglutaric acid Krebs Cycle Does not directly use 02 But considered an aerobic process Breakdown products of fats and proteins can also enter the cycle Kreb s Cycle Each Acetyl CoA that is decarboxylated and oxidized in the Krebs Cycle not including transitional phase generates from 1 glucose molecule the Krebs cycle yields 2 acetyl 00A 2 turns of the Krebs cycle 3 NADH2 molecules which yields 3 ATPNADHZ 1 FADH2 molecules which yields 2 ATPFADHZ 1 ATP 2 002 molecules The Krebs Cycle s principle function is to produce H2 compounds Double all of the products if talking about 1 glucose molecule because it goes into the Krebs cycle 2 times Check your understanding 2 turns of the Krebs cycle directly yields 2 ATP Electron Transport Chain and Oxidative Phosphorylation The part of metabolism that directly uses oxygen but is still considered an aerobic process Substrates NADH2 and FADH2 deliver hydrogen atoms Fueled by the coenzymes Overview of the ETC The general function of the ETC is to synthesize ATP The ETC is fueled by NADH2 and FADH2 molecules formed in the Krebs Cycle As the H s are removedsplit from NADH2 and FADH2 molecules energy is released The energy is used to phosphorylate ADP P ATP NADH2 yields 3 ATPNADH2 FADH2 yields 2 ATPFADH2 when the hydrogen is removed there is a lone electron left on the atom Calculating ATP Production 2 calculations 1 notes NADH2 yields 3 ATP FADH2 yields 2ATP 2 Text USE NOTES CALCULATIONS FOR TEST 9text calculations may be slightly different Electron Transport Chain and Oxidative Phosphorylation Hydrogen atoms are split into H and electrons Electrons are shuttled along the inner mitochondrial membrane losing energy at each step Released energy is used to pump H into the intermembrane space Active transport need ATP to move protons across a membrane When protons are being pumped into the inner membrane space they are being pumped against their concentration gradient Have to maintain a high hydrogen proton concentration gradient on the outside of the cell membrane Electron Transport Chain and Oxidative Phosphorylation Respiratory enzyme complexes I III and IV pump H into the intermembrane space H diffuses back to the matrix via ATP synthase ATP synthase uses released energy to make ATP Gradients want to go from high concentration to low concentration Protons can not freely flow into out of the cell They need to be transported via ATP synthase and create ATP takes longer and is much more complex than substrate level phosphorylation BUT you get a much higher yield of ATP Electronic Energy Gradient Transfer of energy from NADH2 anol FADH2 to oxygen releases large amounts of energy This energy is released in a stepwise manner through the electron transport chain Electron Transport Chain and Oxidative Phosphorylation Electrons are delivered to O forming O O attracts H to form H20 Oxygen is the final electron acceptor CGHQO6 602 9 GHZO 6002 38 ATP heat Oxygen accepts the electrons and we create water Ki xi GI 39 EleztrontraI39r yco ysrs E r port cham 50 L V and oxidative v 39p o Jation 5 FADH2 4 f l Enzyme Complex ll 9 NADH2 unloads its hydrogen at the very first complex Top FADH2 unloads a little further in Therefore we get more ATP from Complex l 30 Free energy relative to 02 kcallmol NADH2 ooenzymes 2 Complex IV because it releases sooner and makes more ATP 10 IMPORTANT SLIDE Y o 3202 Figure 249 ATP Synthase Two major parts connected by a rod 1 Rotor in the inner mitochondrial membrane 2 Knob in the matrix Works like an ion pump in reverse YouTube Oxidative phosphorvlation Intermembrane space 0 0 0 A rotor in the membrane spins clockwise when H flows through it down the H gradient 7 r r o o v a I quotj o 0 I A stator anchored in the membrane holds the knob stationary a a r l I I J I a As the rotor spins a rod connecting the cylindrical rotor and knob also spins The protruding stationary knob contains three catalytic sites that 0 join inorganic phosphate to ADP to make ATP when Mitochondrial matrix the rod is spinning Figure 2411 Glycolysis Final products from 1 glucose molecule 2 pyruvic acid Converted to lactic acid if 02 is not readily available Enter aerobic pathways if 02 is not present 2NADH2 reduced NAD 4 ATP created Transitional phase For every NADH2 ooenzyme we get 3 ATP 1 glucose molecule that enters glyoolysis gives up 2 pyruvio aoids Krebs cycle Each Acetyl CoAthat goes through the Krebs cycle 1 turn 1 acetyl CoA 1 turn 1 turn 3NADH2 1 FADH2 2002 1ATP Multiply by 2 for the 2 Acetyl Co As per 1 glucose molecule to get exact yields MAGIC of aerobic glycolysis 38ATP lmportant to know each initial substrate for each process and the end products Need to understand where the numbers are coming from
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