Cellular Respiration

Cellular Respiration Mr. E. McIntyre

The basics….. Photons chloroplaste Photosynthesis CO2 + H20 Organic Molecules Cell Respiration mitochondrion ATP Thermal Energy

Fermentation Partial breakdown of glucose No mitochondrion Aerobic Respiration Combustion = glucose comburant = O2 ETC (chemiosmosis) Catabolic Pathways (glucose) Breakdown of nutrients Without O2 With O2

Aerobic Respiration The basic equation Sugars + O2  waste + energy C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy

The ATP Principle Phosphate group Price of work in AR: loss of P ATP  ADP + Pi In order to be usable, energy is stored in ATP • adenosine triphosphate • rich in energy.

The ATP Principle ATP… its use ? • Works in membrane transport • Works in kinesin motors • Works in coop. with enzymes ADP + Pi ATP We produce our body weight in ATP on a daily basis!

The REDOX Principle Redox Reactions • Oxidation: loss of e • Reduction: gain of e oxidized energy e C6H12O6 + 6 O2  6 CO2 + 6 H2O + e reduced

Why many REDOX Reactions? Principles of Redox Reactions • Combustion of glucose  many reactions (enzymes) • The alternative in one simple reaction… D’oh ! KaBoOM !!

The e Principle The transfer of e • The e contain a lot of energy! • Passed from one molecule to the next… • Nutrients  NAD+  Electron Transport Chain  O2 e e NADH +H+

The e Principle The transfer of e • Oxidized COenzyme  NAD+ • nicotinamide adenine dinucleotide • The most polyvalent e acceptor oxidized reduced NAD+NADH + H+ Released into cytosol captures 2 e & 1 proton Potential energy

The e Principle esprincipes The transfer of e H2 ½ O2 2 H+ 2 e- Gradual release of energy ATP Energy explosion KaBoOM !! 2 e- ½ O2 2 H+ H2O

Aerobic Cellular Respiration General Principles 4 easy phases :  Glycolysis  Transition Reaction (oxidative decarboxylation)  Krebs Cycle  Electron Transport Chain & Chemiosmosis 1 mole glucose combusted produces … • 6 moles CO2 • 36-38 moles ATP

Aerobic Cellular Respiration electrons electrons Glycolysis Krebs Cycle ETC & chemiosmosis glucose pyruvate ATP ATP ATP

Aerobic Cellular Respiration enzyme (catalyst) Production of ATP • 10%  substrate phosphorylation (phase 1 & 3) • 90%  oxidative phosphorylation (phase 4) Substrate Phosphorylation pyruvate

Part 1 - Glycolysis Glycolysis = « break down of glucose »  Cytosolic reactions  Takes place in the presence or absence of O2 Result 1 mole glucose  2 moles pyruvate (6C) (3C)

Invesment of Energy Phase (endergonic) Phosphorylate the molecule to hydrolyse it into two parts Cost = 2 ATP Payoff of Energy phase (exergonic) Modifications of the 3C molecule  Production = 4 ATP Reduction NAD+ to (2 NADH + 2H+) Part 1 - Glycolysis 2 phases

Part 1 - Glycolysis

Part 1 - Glycolysis 1 glucose 1st Phase Loss 2 ADP 2 ATP Gain 2nd Phase 4 ADP 4 ATP 2 NAD+ 2 NADH + 2H+ 2 pyruvates 2 pyruvates glucose Net Production ø CO2 2 ATP 2 NADH + 2H+

Aerobic Cellular Respiration electrons electrons Glycolysis Krebs Cycle ETC & chemiosmosis glucose pyruvate ATP ATP ATP

Transition Reactions  In the mitochondrion (matrix)  Necessary to begin Citric Acid Cycle

Transition Reactions • Carboxyl's are removed from the pyruvates & released as CO2. • The remaining 2C molecule is further oxidized & the NAD+ is reduced to NADH + H+ (x2). • The COenzyme A bonds to the remaining molecule. • This forms two acetyl-CoA molecules that enter the Krebs Cycle.

Citric Acid Cycle (Tricarboxyllic Acid) • 1 mole acetyl Co-A (2C) enters the cycle… acetyl Co-A (2C) + oxaloacetate (4C) citrate (6C) …further breakdown of citrate back to oxaloacetate

Citric Acid Cycle e acceptors Summary for 1 mole Acetyl Co-A 2 CO2 1 ATP 3 NADH + 3H+ 1 FADH2

Citric Acid Cycle The Krebs Cycle also synthesizes Proteins (AA) Sugars Lipids (FA + chol)

Citric Acid Cycle - Summary 2 CO2 1 ATP 3 NADH + 3H+ 1 FADH2 4 CO2 2 ATP 6 NADH + 6H+ 2 FADH2 x2 pyruvate = Krebs Cycle 2 CO2 Ø ATP 2 NADH + H+ Transition Reactions Glucose completely broken down Majority of energy stored in NADH + H+ 6 CO2 2 ATP 8 NADH + H+ 2 FADH2 = for 1 mole glucose

Respiration cellulaire aérobie electrons electrons Glycolysis ETC & chemiosmosis Krebs Cycle glucose pyruvate ATP ATP ATP

Electron Transport Chain & Chemiosmosis That go between an oxidized & reduced state  In the mitochondrion (cristae) The electron transport chain is comosed of…  proteins  non protein complexes

Electron Transport Chain & Chemiosmosis loses e- ½ O2: last electron acceptor • Captures e- NADH e- lose energy moving through chain

Electron Transport Chain & Chemiosmosis loses e- ½ O2: last electron acceptor • Captures e- NADH e- lose energy moving through chain = formation of H2O

Electron Transport Chain & Chemiosmosis • Other e- carrier FADH2 loses e- at a lower energy level (less energy NADH)

Electron Transport Chain & Chemiosmosis role: synthase ATP • Chemiosmosis • Inner mitochondrial membrane • Uses multiprotein complex known as ATP synthase  oxidative phosphorylation ADP + Pi  ATP

Electron Transport Chain & Chemiosmosis H+ H+ H+ H+ H+ H+ Uses a proton gradient (H+) to synthesize ATP H+  Chemiosmosis  ATP synthetase: proton pump … since the membrane is impermeable to H+

Electron Transport Chain & Chemiosmosis H+ H+ H+ H+ H+ H+ H+  Chemiosmosis intermembrane space  ATP synthetase: proton pump inner mito. membrane The importance of e-?!? Force the displacement of H+ from the matrix to intermembrane space ADP + Pi ATP matrix

Electron Transport Chain & Chemiosmosis NAD+ H+ NADH H+ H+ + H+

Electron Transport Chain & Chemiosmosis H+ NAD+ H+ NADH H+ + H+

Electron Transport Chain & Chemiosmosis H+ H+ NAD+ H+ NADH + H+

Electron Transport Chain & Chemiosmosis H+ H+ H+ 2 H+ + ½ O2 H20 NAD+ NADH + H+ electon transport chain chemiosmosis

Electron Transport Chain & Chemiosmosis ADP + P H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 2 H+ + ½ O2 H20 NAD+ NADH ATP + H+

Aerobic Respiration 3 ATP 2 ATP Chemiosmosis • Ratio in ATP? • NADH + H+ • FADH2

Electron Transport Chain & Chemiosmosis 24 ATP 4 ATP  Chemiosmosis Summary for 1 mole of glucose: • Oxidative decarboxylation & Krebs 2 ATP 8 NADH + H+ 2 FADH2 • glycolyis 2 ATP 2 NADH + H+

Aerobic Respiration transport protein glucose 2 pyruvate • Summary NAD+ ? 2 NADH + H+ FAD ? 2 NADH + H+ 6 NADH + H+ 2 FADH2 glycolysis Electron Transport Chain Krebs Cycle TR 2 acétyle Co-A 2 ATP 2 ATP 32 ou 34 ATP 36 or 38 ATP

Other Metabolic Processes • Fermentation • Glucose metabolism without O2 • Summary 1 mole glucose 2 ATP 2 pyruvate 2 NADH + H+

Other Metabolic Processes • Fermentation • Alcolholic Fermentation Ex: production beer, wine, spirits

Other Metabolic Processes Fermentation • Lactate Fermentation Ex: production of cheese & yogurt Ex: lactate in muscles

Other Metabolic Processes • Fermentation Comparison of aerobic respiration & fermentation  fermentation: last electron acceptor pyruvate dioxygen  aerobic respiration…  anaerobicrespiration … nitrate (NO3-) sulfate (SO42-) fer (Fe3+) Which is the most efficient? You do the math! 38 ATP vs 2 ATP

Metabolic Poisons death of the organism death of the organism • cyanide  denatures enzyme cytochrome c oxidase final transport of electrons from cytochrome c oxidase to oxygen cannot be completed  electrons cannot be removed; cell relies on anaerobic respiration • dicoumarol  inhibits mitochondrial electron transport  reversed electron flow in Complex II  inhibits pyrimidines biosynthesis

Other Metabolic Pathways Something to think about

Phew…..many ATP were synthesized in the making of this presentation!

Cellular Respiration