Aerobic Respiration• Four Stages in Aerobic Respiration – Glycolysis Series of reactions; products from these – Link reaction reactions are used in final stage – to produce ATP – Krebs cycle Last three occur in the mitochondria – (Glycolysis in the – Oxidative phosphorylation cytoplasm) Cristae Inner membrane Matrix Outer membrane
Stage one, GlycolysisGlycolyisis makes Pyruvate Glycolysis from Glucose• Glycolysis involves splitting 1 molecule of glucose (6C) Link reaction into 2 smaller molecules of pyruvate (3C).• Occurs in the cytoplasm Krebs cycle• The first stage of both aerobic and anaerobic Oxidative and doesn’t need oxygen phosphorylation to take place – anaerobic process
2 Stages of GlycolysisStage 1: Phosporylation glucose (6C)1) Glucose is 2ATP phosphorylated by adding 2 phosphates from 2 2ADP molecules of ATP hexose biphosphate (6C)2) This creates 1 molecule of hexose bisphosphate and 2x triose phosphate (3C) 2 molecules of ADP 4ADP+4P 2H+ 2NAD3) Then, hexose bisphosphate is split up 4ATP 2reducedNAD into 2 molecules of triose phosphate. 2x pyruvate (3C)
2 Stages of GlycolysisStage 2: Oxidation glucose (6C)• Triose phosphate is 2ATP oxidised, forming 2 molecules of pyruvate. 2ADP• NAD collects the hydrogen hexose biphosphate (6C) ions, forming 2 reduced NAD 2x triose phosphate (3C)• 4 ATP are produced, but 2 4ADP+4P 2H+ 2NAD were used up in stage one so there’s a net gain of 2 4ATP 2reducedNAD ATP. 2x pyruvate 3C
Stage 2, the link reactionLink reaction occurs in mitochondrial matrix pyruvate (3C)• Pyruvate is decarboxylated – CO2 (1C) one carbon atom is removed from pyruvate in the form of CO2 NAD• NAD is reduced – it collects reduced NAD hydrogen from pyruvate, changing pyruvate to acetate acetate (2C)• Acetate is combined with coenzyme A (CoA) coenzyme A (CoA) to form acetyl coenzyme A (acetyl CoA)• No ATP is produced in this acetyl CoA (2C) reaction
Link reactionThe Link Reaction occurs twice for every glucose molecule Glycolysis• Two molecules of acetyl coenzyme A go into Krebs cycle Link reaction• Two CO2 molecules are released as a waste product of respiration Krebs cycle• Two molecules of reduced NAD are formed and go to the Oxidative last stage (oxidative phosphorylation phosphorylation)
MitochondriaMitochondria are adapted to their function:• Inner membrane is folded into cristae, which increases membrane’s surface area to maximise respiration• There are lots of ATP Synthase molecules in the inner membrane to produce lots of ATP in the final stage of respiration• The matrix contains all the reactants and enzymes needed for the Krebs cycle to take place. Cristae – increase Inner membrane – surface area to lots of ATP maximise synthase molecules respiration in here to produce lots of ATP in final stage Matrix – contains all the reactants Outer membrane and enzymes needed for the Krebs cycle
Stage 3, the Krebs CycleThe Krebs cycle produces Reduced Coenzymes and ATP1) – Acetyl CoA from the link reaction combines with oxaloacetate to form citrate – Coenzyme A goes back to the link reaction to be used again Acetyl CoA (2C) CoA Oxaloacetate (4C) Citrate (6C) CO2 (1C) reduced NAD NAD reduced FAD NAD FAD ATP reduced NAD ADP + Pi 5C compound reduced NAD
Stage 3, the Krebs Cycle2) Acetyl CoA (2C) – the 6C citrate CoA molecule is converted to a 5C molecule Oxaloacetate (4C) Citrate (6C) – Decarboxylation CO2 (1C) occurs where CO2 is reduced NAD NAD removed reduced FAD FAD NAD – Dehydrogenation also ATP reduced NAD occurs where hydrogen ADP + Pi reduced NAD 5C compound is removed NAD CO2 (1C) – The hydrogen is used to produce reduced NAD from NAD
Stage 3, the Krebs Cycle3) Acetyl CoA (2C) – The 5C molecule is then CoA converted to a 4C molecule (there are some intermediate compounds formed during this conversion) Oxaloacetate (4C) Citrate (6C) – Decarboxylation and dehydrogenation occur, producing CO2 (1C) one molecule of reduced FAD reduced NAD and two of reduced NAD NAD – ATP is produced by the direct reduced FAD FAD NAD transfer of a phosphate group ATP reduced NAD from an intermediate compound ADP + Pi 5C compound to ADP reduced NAD NAD – When a phosphate group is CO2 (1C) directly transferred from one molecule to another it’s called substrate-level phosphorylation. – Citrate has now been converted to oxaloacetate.
Stage 3, the Krebs cycle• The Krebs cycle involves a Glycolysis series of oxidation- reduction reactions which takes place in the matrix of Link reaction the mitochondria.• The cycle happens once Krebs cycle for every pyruvate molecule, it goes round Oxidative twice for every glucose phosphorylation molecule
Products of the Krebs cycle• Some of the products of the Krebs cycle are used in Oxidative Phosphorylation Products from one Krebs cycle Where it goes 1 x coenzyme A Reused in next link reaction Oxaloacetate Regenerated for use in the next Krebs cycle 2 x CO2 Released as a waste product 1 ATP Where it goes 3 reduced NAD Reused in next link reaction 1 reduced FAD Regenerated for use in the next Krebs cycle
Stage 4, Oxidative Phosphorylation• Produced lots of ATP• Process where the energy Glycolysis carried by electrons from reduced coenzymes (reduced NAD and reduced FAD) is used Link reaction to make ATP. (The whole point of the previous stages is to make reduced NAD and reduced FAD Krebs cycle for the final stage)• (Oxidative phosphorylation Oxidative involves 2 processes – electron phosphorylation transport chain and chemieosmosis.
Stage 4, Oxidative PhosphorylationProtons are pumped across the inner Mitochondrial Membrane.• Hydrogen atoms are released from reduced NAD and reduced FAD as they’re oxidised to NAD and FAD – H atoms split into protons and electrons (H+ and e-)• e- move along electron transport chain (made up of 3 electron carriers) losing energy at each carrier.• This energy is used by electron carriers to pump protons from the mitochondrial matrix into the intermembrane space (space between the inner and outer mitochondrial membranes)• Concentration of protons is now higher in the intermembrane space than the mitochondrial matrix - forms an electrochemical gradient• Protons move down the electrochemical gradient back into the matrix via ATP synthase - this movement drives the synthesis of ATP from ADP and inorganic phosphate.• Movement of H+ across a membrane, generates ATP = CHEMIOSMOSIS• In matrix, at ed of transport chain the protons, electrons and O2 combine with water Oxygen is said to be the final electron acceptor
Stage 4, Oxidative Phosphorylationouter mitochondrial membrane high H+ concentration H+ H+ H+ H+ H+ H+ H+innermembrane space H+ H+ H+inner mitochondrial membranematrix of mitochondrion ADP + Pi 2e- reduced NAD 2H 2e- ATP H2O NAD H+ H+ H+ H+ 2H+ ATP H+ syntase low H+ concentration ½ O2 + 2H-
one mole of glucose makes 38 atp ELECTRON TRANSPRORT CHAINGYCOLYSIS2 ATP ALL TOGETHER2 NADH 4 ATPLINK REACTION1 NADH x 2 2NADH 1 NADH = 3 ATP 30 ATP 10 NADH 1 FADH2 = 2 ATPKREBS CYCLE 2 FADH2 4 ATP1 ATP x2 2ATP3 NADH x2 6NADH1 FADH2 x2 2 FADH2