Respiration Respiration Involves : Glycolysis, Krebs cycle, Electron transport and Oxidative Phosphorylation
INTRODUCTION Glycolysis : Occurs in the cytoplasm. Breaks glucose into two molecules of pyruvate. Krebs cycle : occurs in the mitochondrial matrix. degrades pyruvate to carbon dioxide. Several steps in glycolysis and the Krebs cycle transfer electrons from substrates to NAD+, forming NADH. NADH passes these electrons to the electron transport chain.
Mitochondria stage 3rd of respiration Occurs in mitochondria.
Mitochondria Outer membrane- permeable to small molecules Inner membrane- electron transport ATP synthase Cristae increase area Integrity required for coupling ETS to ATP synthesis
Mitochondria outer membrane relatively permeable inner membrane permeable only to those things with specific transporters ◦ Impermeable to NADH and FADH2 ◦ Permeable to pyruvate Compartmentalization ◦ Krebs and β-oxidation in matrix ◦ Glycolysis in cytosol
Electron Transport System Electron Transport Chain – is a collection of molecules embedded in the inner membrane of the mitochondria ◦ Most components are proteins
Electron Transport System Mechanism the cell that converts the energy in NADH and FADH2 into ATP. Electrons flow along an energy gradient via carriers in one direction from a higher reducing potential to a lower reducing potential The ultimate acceptor is molecular oxygen. At the end of the chain electrons are passed to oxygen forming water.
Electron Transport System An NADH molecule begins the process by “dropping off” its electron at the first electron carrier molecule
ETS Remember: each component will be 50 NADH reduced when it accepts 40 I FADH2 FAD Multiprotein FMN complexes Free energy (G) relative to O2 (kcl/mol) the electron and oxidized Fe•S O Fe•S Cyt b II III when it passes the 30 Fe•S Cyt c1 Cyt c IV electron down to the more 20 Cyt a Cyt a3 electronegative carrier molecule in the chain 10 0 2 H ++ 12 O2 H2 O
Finally the electron is passed tooxygen, which is very electronegative. NADH 50 FADH2 I Multiprotein 40 FAD Free energy (G) relative to O2 (kcl/mol) FMN complexes Fe•S II The oxygen also picks Fe•S O Cyt b III Fe•S up 2 H+ ions from the 30 Cyt c1 Cyt c IV Cyt a aqueous solution and 20 Cyt a3 forms water 10 0 2 H ++ 12 O2 H2 O
ETS FADH goes through 50 NADH mostly the same FADH2 Multiprotein Free energy (G) relative to O2 (kcl/mol) 40 I FAD processes, except it FMN complexes Fe•S Fe•S II O III Cyt b drops off its electron 30 Fe•S Cyt c1 Cyt c IV at a lower point on Cyt a Cyt a3 20 the ETC 10 0 2 H ++ 12 O2 H2O
The ETC makes no ATP directly!The ETC releases energy in a step-wise series of reactionsIt powers ATP synthesis via oxidativephosphorylation.But it needs to be coupled withchemiosmosis to actually make ATP.
Oxidative PhosphorylationProduction of ATP usingtransfer of electrons for energy Some ATP is produced by substrate-level phosphorylation during glycolysis and the Krebs cycle, but most comes from oxidative phosphorylation
Oxidative phosphorylation CONCEPT : During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis
Chemiosmosis The Energy-Coupling Mechanism Inner membrane of mitochondria has many protein complexes called ATP synthase ◦ ATP synthase – enzyme that makes ATP from ADP and inorganic phosphate It uses the energy of an existing gradient to do this.
The existing gradient is the difference in H+ ion concentration on opposite sides of the inner membrane of the mitochondria Inner Mitochondrial Oxidative Glycolysis phosphorylation. membrane electron transport and chemiosmosis ATP ATP ATP H+ H+ H+ H+ Protein complex Cyt cIntermembrane of electronspace carners Q IV I III ATPInner II synthasemitochondrial FADH2 FAD+ 2 H+ + 1/2 O2 H2Omembrane NADH+ NAD+ ADP + Pi ATP (Carrying electrons from, food) H+Mitochondrial Electron transport chain Chemiosmosismatrix Electron transport and pumping of protons (H +), ATP synthesis powered by the flow which create an H+ gradient across the membrane Of H+ back across the membrane Oxidative phosphorylation
Chemiosmosis Chemiosmosis – the process in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work (like the synthesis of ATP)
It is the job of the ETC to create this H+ ion gradient Inner Mitochondrial Oxidative Glycolysis phosphorylation. membrane electron transport and chemiosmosis ATP ATP ATP H+ H+ H+ H+ Protein complex Cyt cIntermembrane of electronspace carners Q IV I III ATPInner II synthasemitochondrial FADH2 FAD+ 2 H+ + 1/2 O2 H2Omembrane NADH+ NAD+ ADP + Pi ATP (Carrying electrons from, food) H+Mitochondrial Electron transport chain Chemiosmosismatrix Electron transport and pumping of protons (H+), ATP synthesis powered by the flow which create an H+ gradient across the membraneOf H+ back across the membrane Oxidative phosphorylation
H+ ions are pumped into theintermembrane space by the ETCThe H+ ions want to drift back into thematrix.But they can only come into the matrixeasily through ATP synthase channels
A protein complex, ATPsynthase, in the cristaeactually makes ATP fromADP and Pi.ATP used the energy ofan existing proton gradientto power ATP synthesis. proton gradientdevelops between theintermembrane spaceand the matrix.
Mitochondrial redox carrierNADH Complex I Q Complex III Complex IIComplex IV FADHO2
4 Complexes proteins in specific order Transfers 2 electrons in specific order ◦ Proteins localized in complexes Embedded in membrane Ease of electron transfer ◦ Electrons ultimately reduce oxygen to water 2 H+ + 2 e- + ½ O2 -- H2O
Complex I Has NADH binding site ◦ NADH reductase activity NADH - NAD+ ◦ transfers to electron carriers ◦ NADH (nicotinamide adenine dinucleotide )
Passes them to coenzyme Q ( Ubiquinone )Also receive electron from complex II
Complex II succinate ---FAD—ubiquinone ◦ Contains coenzyme Q ◦ FADH2 binding site FAD reductase activity FADH2 -- FAD conversion of succinate to fumerate