So what is going to be used in the next stage to produce what??? Starter: RECAP RESPIRATION SO FAR.... What are the total end products of each stage? Glycolysis Link reaction and Krebs cycle So what is going to be used in the next stage to produce what???

Overall glycolysis produces: 2x ATP, 2x 2H atoms 2x 3C pyruvate molecules KREBS is 2x for each glucose molecule: 2 pyruvate Link reaction: 2x CO², 2x 2H removed (reduced NAD) and 1x 2C compound combines with coenzyme A= 2x acetyl CoA Krebs cycle: 2x 4C compound oxaloacetate; 4x CO², 2x ATP molecule; 2x reduced FAD, 6x reduced NAD

Oxidative Phosphorylation The fate of the hydrogen ions The electron transport chain And the production of ATP! Watch: http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_1_.html

Learning outcomes: Describe the process of oxidative phosphorylation, with reference to the roles of electron carriers, oxygen and the mitochondrial cristae; Outline the process of chemiosmosis, with reference to the electron transport chain, proton pumps and ATPase Explain that oxygen is the final electron acceptor in aerobic respiration; Explain that the theoretical yield of ATP per glucose molecule is rarely achieved

Oxidative Phosphorylation Includes the respiratory chain or electron transport chain This takes place on the inner membrane of the mitochondria Folded into cristae, increasing the surface area for electron carriers and ATP synthase enzymes This is the MAJOR source of ATP in aerobic organisms Inner membrane

Oxidative Phosphorylation: The electron transport chain Oxidative phosphorylation is the formation of ATP by adding a phosphate group to ADP, in the presence of oxygen which is the final electron acceptor

Chemiosmosis How the electron transport chain leads to production of ATP is explained by chemiosmosis Energy is released as e- pass along electron transport chain This energy moves H+ ions from matrix, across inner mitochondrial membrane to the intermembrane space This causes a steep electrochemical gradient across the inner membrane Large difference in H ion concentration Large electrical difference SO WHAT HAPPENS??

Chemiosmosis SO WHAT HAPPENS?? Intermembrane space is more +ve Protons/H+ ions diffuse down electrochemical gradient Through hollow protein channels in stalked particles on the inner membrane As H+ ions pass through, ATP synthesis is catalysed by ATPase located in each stalked particle The H+ ions cause a change in shape of the enzymes active site, so ADP can bind

Chemiosmosis Within matrix H+ ions + e- combine=hydrogen atoms Hydrogen atoms + oxygen= water The oxygen is the final carrier in the electron transport chain is reduced

Tasks: Define oxidative phosphorylation and chemiosmosis Summarise in a flow diagram the process of oxidative phosphorylation and chemiosmosis

Chemiosmosis: The flow of hydrogen ions (protons) through ATP synthase enzymes. The force of this flow produces ATP. Oxidative phosphorylation: formation of ATP by adding a phosphate group to ADP in the presence of oxygen, which is the final electron acceptor.

A summary of where respiration occurs

How much ATP is produced? The total yield of ATP from the complete oxidation of glucose Each rNAD=3ATP, rFAD=2ATP Source of ATP ATP yield per glucose molecule Glycolysis Krebs Cycle ..... x NADH formed in glycolysis .... . x NADH formed in link reaction ...... x FADH2 formed in Krebs cycle ...... x NADH formed in Krebs Cycle Total ATP yield

Oxidative Phosphorylation The total yield of ATP from the complete oxidation of glucose Each rNAD=3ATP, rFAD=2ATP Source of ATP ATP yield per glucose molecule Glycolysis +2 (substrate) Krebs Cycle 2 X NADH formed in glycolysis +6 2 X NADH formed in link reaction 2 X FADH2 formed in Krebs cycle +4 6 X NADH formed in Krebs Cycle +18 Total ATP yield +38

What is remaining energy used for? How much ATP? Accepted that this is not accurate... Electrochemical gradient involves other ions/molecules So not all H+ ions are available for ATP synthesis Some ions leak across membrane Some ATP is used to actively transport pyruvate into mitochondrial matrix Some ATP used to shuttle the hydrogen made during glycolysis in cytoplasm into mitochondrial matrix Believed to be 30 ATP 32% of the potential chemical energy stored in glucose What is remaining energy used for? TEMP of cell! Increases rate of reactions!

Tasks: Exam questions Chemiosomosis question: 6 marks Oxidative phosphorylation exam question! None on OCR….this year?? 6 marks=6 minutes

Evaluating the evidence for chemiosomosis Define: Diffusion of ions through a partially permeable membrane. Flow of protons across a membrane coupled with the production of ATP during respiration Takes place on inner mitochondrial membrane in Eukaryotic cells and on mesosomes in Prokaryotic cells

Peter Mitchell 1961: Chemiosmosis theory The build up of hydrogen ions on one side of membrane= potential source of energy Movement of ions across the membrane down an electrochemical gradient= energy to power formation of ATP from ADP and Pi Inner mitochondrial membrane= energy transducing membrane Proposed proton motive force theory: energy released from transfer of electrons along ETC is used to pump H ions from matrix to inner mitochondrial space H ions then flow back into matrix down a concentration gradient through proton channels attached to enzymes

Scepticism!! Evidence by 1978…………. Mitchel achieved the Nobel prize for chemistry Since then scientists have established that the stalked particles are ATP synthase enzymes and how they function Also that some of the complexes in ETC have coenzymes that can use energy released from ETC to pump H ions into intermembrane space

Evidence from other studies: Mitochondria placed in solutions of high water potential: water diffused into organelle, outer membrane ruptured, releasing contents of intermembrane space These mitoplasts treated with detergent to rupture inner membrane= matrix contents Identified where enzymes in mitochondria are, so where each reaction took place

Electron transfer in mitoplasts produced very little ATP= intermembrane space involved ATP not made if mushroom part of stalked particles was removed ATP not made in the presence of an antibiotic (oligomycin) which blocks proton flow through ion channel part of stalked particle

In intact mitochondria: Potential difference across inner membrane = -200mV More negative on matrix side than on intermembrane side pH of intermembrane space was lower than that of matrix

Why was there a time lag 1961 to 1978 between the proposed theory and its general acceptance? Other scientists carried out work, new or repeated Evidence gathered to support the theory More studies are replicated, the more reliable the evidence is

Task Check your understanding by answering and checking your answers to page 93