Cellular Respiration Chapter 3 Where did Bruce Lee get all that energy from?

What is it? Cellular respiration –An aerobic process (requires oxygen) –Uses chemical energy from glucose to make ATP –Chemical energy is now stored in ATP for use throughout the body O2O2 ATP 36 glucose 1 Cellular resp.

Four Main Stages 1.Glycolysis Anaerobic In cytosol breaks glucose (6C) into 2 pyruvate molecules (3C) releases ATP 2.Transition reaction (oxidative decarboxylation) Pyruvate converted to acetyl CoA releasing CO 2 3.Kreb’s Cycle Within mitochondrial matrix Oxidize each acetyl CoA to CO 2 Releases ATP and co-enzymes (NADH, FADH 2 ) 4.Electron Transport Chain Along the inner mitochondrial membrane Uses high energy electrons from NADH and FADH 2 to create an electrochemical proton (H + ) gradient which powers ATP synthesis

Fermentation When oxygen is NOT available, cells can metabolize pyruvate (derived from glucose) by the process of fermentation. Two Types (i) alcohol fermentation: pyruvate (3C) converted (reduced) to ethyl alcohol (2C) and CO 2 ; occurs in yeast cells (ii) lactic acid fermentation: pyruvate(3C) converted (reduced) to lactic acid (3C) in muscle cells

Cellular Respiration glucose + O 2  CO 2 + H 2 O + energy CO 2 H2OH2O H+H+ H+H+ Energy O2O2 glucose General Formula This process begins with glucose. Once it enters a cell, the process of glycolysis begins immediately in the cytoplasm where enzymes are waiting.

Glycolysis (I) Overview This is the investment period of glycolysis ATP is USED in order to “activate” glucose This is accomplish by an enzyme mediated process called: substrate level phosphorylation »Involving the transfer of a phosphate group

Numbering the Carbons of Glucose glucose C C CC C O C In order to keep track of how glucose is modified and rearranged during glycolysis we number each carbon

PPP glucose C C CC C O C C C CC C O C PP P C C C C O CP C C C C C O CP C P CCCPCCCP PPP PP C C CC C O CP glucose-6-phosphate fructose-6-phosphate fructose-1-6-bisphosphate 2 molecules of PGAL (glyceraldehyde-3-phosphate) Glycolysis (I)

glucose C C CC C O C C C CC C O C P C C C C O CP C C C C C O CP C P CCCPCCCP glucose-6-phosphate fructose-6-phosphate fructose-1-6-biphosphate 2 molecules of PGAL (glyceraldehyde-3-phosphate) activation isomerization activation cleavage ADP ATP ADP ATP

Glycolysis (I) 1. Activation: Phosphate from ATP is added to glucose to form glucose-6-phosphate. [substrate-level phosphorylation] 2. Isomerization: Glucose-6-phosphate is rearranged to form fructose-6-phosphate. 3. Activation: A second phosphate from another ATP is added to form fructose-1,6-bisphosphate. [substrate-level phosphorylation] 4. Cleavage: The unstable fructose-1,6- bisphosphate splits into phosphoglyceraldehyde (PGAL) and dihydroxyacetone phosphate (DHAP). Investment

Glycolysis (II) Overview This is the pay-off period of glycolysis ATP and NADH (a high energy molecule) are PRODUCED during glycolysis II By the end of glycolysis II, glucose has been broken down from 6 carbons to a 3 carbon compound called Pyruvate (pyruvic acid)

Glycolysis (II) CCCPCCCPCCCPCCCPPPCCCPCCCP NAD NADH NAD NADH PiPi PiPi PPP PP PPCCCPCCCP PPP PP CCC P CCC P PPP PP PPP PP PPCCCCCC PGAL PGAP PGA PEP Pyruvate H2OH2O H H H2OH2O H H

Glycolysis (II) CCCPCCCPCCCPCCCPPPCCCPCCCP NADH PPCCCPCCCP CCC P CCC PPPCCCCCC PGAL PGAP PGA PEP Pyruvate ATP activation / redox dephosphorylation isomerization / dehydration dephosphorylation H2OH2O H H H2OH2O H H

5. Activation/Redox: Each molecule of PGAL is oxidized by NAD and gains a phosphate to form 1,3-bisphosphoglycerate (PGAP). 6. Phosphorylation: Each PGAP loses a phosphate to ADP resulting in 2 ATP and two 3-phosphoglycerate molecules (3-PGA).[substrate-level phosphorylation] 7. Isomerization: Both 3-PGA molecules are rearranged to form 2-phosphoglycerate (2-PGA). [note: the text does not distinguish between 3-PGA and 2-PGA, but refers to both as PGA] 8. Dehydration: Both 2-PGA molecules are oxidized to phosphoenol pyruvate (PEP) by the removal of water. 9. Phosphorylation: Each PEP molecule loses a phosphate to ADP resulting in 2 more ATP and 2 molecules of pyruvate. [substrate-level phosphorylation] Glycolysis (II) Pay-off

The Result Energy in Glycolysis Used 2 ATP Made 4 ATP Net Gain: 4 ATP – 2 ATP = And ATP 2 NADH 2 (high energy molecule)

Notice: There is no oxygen used in glycolysis. It is an anaerobic process Glycolysis: overall reaction C 6 H 12 O 6 + 2ADP + 2P + 2NAD +  2C 3 H 4 O 3 + 2NADH + 2ATP glucose (6C)pyruvate (3C) O2O2

The Power House! In the cytosol, for each glucose molecule consumed, only 2 ATP were produced This means that 34 more ATP are made in the mitochondria! How do we get in there and what happens inside!? nucleus mitochondria cytosol ATP

Inside the Mitochondria

outer membrane: contains transport protein porin, which affects permeability inner membrane: contains the phospholipid cardiolipin that makes membrane impermeable to ions, a condition which is required for ATP production intermembrane space: fluid-filled area containing enzymes and hydrogen ions matrix: location of Kreb’s Cycle cristae: folds of the inner membrane where ETC enzymes are found

Transition Reaction Intermembrane space mitochondrion C – C – C pyruvate multi-enzyme pyruvate dehydrogenase complex

Transition Reaction mitochondrion C – C – C pyruvate 1. Decarboxylation C – C CO 2 Intermembrane space

Transition Reaction mitochondrion 2. Oxidation C – C NAD + C – C NADH Intermembrane space

Transition Reaction mitochondrion 3. Attachment C – C CoA Intermembrane space

Transition Reaction mitochondrion 3. Attachment C – C CoA Acetyl CoA Intermembrane space

Transition Reaction A.Decarboxylation (-CO2) of pyruvate leaving a 2C molecule B.Oxidation by NAD+ forming an acetate molecule. C.Attachment of coenzyme A forming acetyl coA. Steps A and B together are referred to as oxidative decarboxylation

Transition Reaction In the transition reaction, for each molecule of pyruvate: CO 2 1 is released and NADH 1 is produced

Transition Reaction Remember: There are 2 pyruvates produced for each glucose. Therefore, for each glucose: CO 2 1 is released and NADH 1 is produced CO 2 2 are released and NADH 2 are prodcued X2

Krebs Cycle 1. Acetyl coA breaks into coenzyme A, which is recycled, and an acetyl group (2C) which joins to oxaloacetate (4C) forming citrate (6C). 2. Citrate (6C) converts to isocitrate (6C). 3. Isocitrate (6C) loses CO 2 and is then oxidized by NAD forming alpha-ketoglutarate (5C). [oxidative decarboxylation] 4. Alpha-ketoglutarate (5C) is converted to succinyl-coA (4C) in 3 steps: (i) loss of CO 2 (ii) oxidation by NAD+ (iii) attachment of coenzyme A

Krebs Cycle 5. Succinyl coA (4C) is converted to succinate (4C) in the following way: - coenzyme A breaks off and is recycled; phosphate attaches temporarily to succinate and is then transferred to GDP forming GTP; GTP transfers phosphate to ADP forming ATP (substrate level phosphorylation). 6. Succinate (4C) is oxidized by FAD to form fumarate (4C). 7. Water is added to fumarate (4C) to form malate (4C). 8. Malate (4C) is oxidized by NAD+ to form oxaloacetate, which is regenerated to begin the cycle again.

Krebs Cycle Transition reaction Krebs Cycle

In the Krebs Cycle for each molecule of pyruvate: CO 2 2 are released NADH 3 and FADH 2 1 ATP 1 are produced

Krebs Cycle Remember: There are 2 pyruvates produced for each glucose. Therefore, for each glucose: CO 2 2 are released NADH 3 and FADH 2 1 ATP 1 are prodcued CO 2 4 are released NADH 6 and FADH 2 2 ATP 2 are produced X2

The Story So Far glucose 1 C – C – C pyruvate 2 CO 2 6 Tracking carbon: (6C) (3C) (1C)

The Story So Far Tracking High Energy Molecules Metabolic ProcessATP ProducedHigh Energy Molecules Glycolysis Transition Reaction (x2) (oxidative decarboxylation) Krebs Cycle (x2) Total NADH 2 ATP 2 NADH 6 FADH 2 2 ATP 2 NADH 2 in cytosol ATP 4 NADH 10 FADH 2 2

Using the High Energy Molecules NADH and FADH 2 have gained high energy electrons These electrons are donated to electron carrier proteins in the Electron Transport Chain (ETC). The energy from these electrons is then used to pump protons (H + ) into the intermembrane space of the mitchondria

ATP Synthase Electron Transport Chain Electron Carriers: 1. NADH reductase [protein] 2. Coenzyme Q [non-protein] 3. Cytochrome b 1 c 1 4. Cytochrome c 5. Cytochrome c oxidase Cristae Q C NADH reductase Co-enzyme Q Cytochrome b 1 c 1 Cytochrome c Cytochrome c oxidase [protein] not part of the ETC

Electron Transport Chain To pass electrons along ETC, each carrier is reduced (gains electrons) then oxidized (donates electrons) Curious? Where do these electrons come from? Electrons come from hydrogen atoms (H atoms separate into electrons and protons) Cristae Q C

Electron Transport Chain 1)NADH donates a pair of electrons to NADH reductase 2)electrons continue along ETC via sequential oxidations and reductions Cristae Q C NADH NAD +

Electron Transport Chain 1)FADH 2 donates a pair of electrons to coenzyme Q 2)electrons also continue along ETC Cristae C Q FADH 2

Electron Transport Chain Cristae C Q 1)FADH 2 donates a pair of electrons to coenzyme Q 2)electrons also continue along ETC

For each NADH, 6 H + are pumped across the mitochondrion inner membrane Cristae Q C NADH NAD + H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ For each NADH, 6 H + are pumped across the mitochondrion inner membrane Oxygen is the final electron acceptor and is converted to H 2 O O2O2 H2OH2O H+H+ H+H+

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ For each FADH 2, 4 H + are pumped across the mitochondrion inner membrane O2O2 H2OH2O H+H+ H+H+ FADH 2

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ The electrochemical proton gradient (sometimes referred to as the proton motive force) H+H+ H+H+ H+H+ H+H+ High Proton Concentration Low Proton Concentration Gradient

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Using the energy stored in the proton gradient, ATP is generated using oxidative phosphorylation: formation of ATP coupled to oxygen consumption H+H+ H+H+ H+H+ H+H+ ATP Using the electrochemial proton gradient to produce ATP from ADP is called chemiosmosis

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ 1 ATP is generated for each proton pair flowing through ATP synthase. H+H+ H+H+ H+H+ H+H+ ATP NADH Pumps H+H+ H+H+ 6 ATP 3

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ 1 ATP is generated for each proton pair flowing through ATP synthase. H+H+ H+H+ H+H+ H+H+ ATP FADH 2 Pumps H+H+ H+H+ 4 ATP 2

ATP synthase works a bit like a water mill

The WHOLE process… Cristae Q C H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+

The WHOLE process… Cristae Q C NADH NAD + H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ O2O2 H2OH2O H+H+ H+H+ The WHOLE process…

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP The WHOLE process…

Cristae C Q H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP The WHOLE process…

Summing up ATP Remember: BEFORE the ETC we had… Metabolic ProcessATP ProducedHigh Energy Molecules Glycolysis Transition Reaction (x2) (oxidative decarboxylation) Krebs Cycle (x2) Total NADH 2 ATP 2 NADH 6 FADH 2 2 ATP 2 NADH 2 in cytosol ATP 4 NADH 10 FADH 2 2

Summing up ATP In the Electron Transport Chain Molecules fromHigh Energy Molecules ATP produced in ETC Glycolysis Transition Reaction (x2) (oxidative decarboxylation) Krebs Cycle (x2) Total NADH 2 6 FADH 2 2 NADH 2 in cytosol NADH 10 FADH 2 2 ATP ATP 32

Summing up ATP IN TOTAL Molecules fromHigh Energy Molecules ATP produced in ETC Glycolysis Transition Reaction (x2) (oxidative decarboxylation) Krebs Cycle (x2) Total NADH 2 6 FADH 2 2 NADH 2 in cytosol NADH 10 FADH 2 2 ATP ATP 32 ATP 34 ATP 2 + From Glycolysis ATP 2

Summing up ATP IN TOTAL Molecules fromHigh Energy Molecules ATP produced in ETC Glycolysis Transition Reaction (x2) (oxidative decarboxylation) Krebs Cycle (x2) Total NADH 2 6 FADH 2 2 NADH 2 in cytosol NADH 10 FADH 2 2 ATP ATP 34 ATP 36 ATP From Krebs Cycle ATP 2

glucose + oxygen carbon dioxide + water + energy Overall Reaction glucose 1 CO 2 6 NAD + 10 FAD 2 NADH 10 FADH 2 2 NAD + 10 FAD 2 O2O2 H2OH2O H+H+ H+H+ Catalysts ATP 36 glucose O2O2 CO 2 Energy H2OH2O H+H+ H+H+

glucose + oxygen carbon dioxide + water + energy Overall Reaction glucose 1 CO 2 6 NAD + 10 FAD 2 O2O2 H2OH2O H+H+ H+H+ ATP 36 Phase (location) Glycolysis (cytosol) Transition Reaction (mito.) Kreb’s Cycle (mito.) ETC (mito.) some