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Harvesting stored energy Glucose is the model –catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates)

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Presentation on theme: "Harvesting stored energy Glucose is the model –catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates)"— Presentation transcript:


2 Harvesting stored energy Glucose is the model –catabolism of glucose to produce ATP C 6 H 12 O 6 6O 2 ATP6H 2 O6CO 2  + ++ CO 2 + H 2 O + heat fuel (carbohydrates) COMBUSTION = making a lot of heat energy by burning fuels in one step RESPIRATION = making ATP (& some heat) by burning fuels in many small steps CO 2 + H 2 O + ATP (+ heat) ATP glucose glucose + oxygen  energy + water + carbon dioxide respiration O2O2 O2O2 + heat enzymes ATP

3 2 ATP = adenosine triphosphate -the energy “currency” of cells ATP stores energy in the bonds between phosphates

4 3 Energy Currency of Cells When the bond between phosphates is broken: ATP ADP + P i energy is released ADP = adenosine diphosphate P i = inorganic phosphate This reaction is reversible.

5 ATP Really high energy bond ADP + P i

6 How do we harvest energy from fuels? Digest large molecules into smaller ones –break bonds & move electrons from one molecule to another as electrons move they “carry energy” with them that energy is stored in another bond, released as heat or harvested to make ATP e-e- ++ e-e- +– loses e-gains e-oxidizedreduced oxidationreduction redox e-e-

7 How do we move electrons in biology? Moving electrons in living systems –electrons cannot move alone in cells electrons move as part of H atom move H = move electrons p e + H + H +– loses e-gains e-oxidizedreduced oxidationreduction C 6 H 12 O 6 6O 2 6CO 2 6H 2 OATP  +++ oxidation reduction H e-e-

8 Moving electrons in respiration Electron carriers move electrons by shuttling H atoms around –NAD +  NADH (reduced) –FAD +2  FADH 2 (reduced) + H reduction oxidation P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H adenine ribose sugar phosphates NAD + nicotinamide Vitamin B3 niacin P O–O– O–O– O –O–O P O–O– O–O– O –O–O C C O NH 2 N+N+ H NADH carries electrons as a reduced molecule reducing power! How efficient! Build once, use many ways H

9 8 Steps of Respiration The complete oxidation of glucose proceeds in stages: 1. glycolysis 2. pyruvate oxidation 3. Krebs cycle 4. electron transport chain & chemiosmosis

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11 Glycolysis glucose      pyruvate 2x2x 6C3C That’s not enough ATP for me! Breaking down glucose –“glyco – lysis” (splitting sugar) –ancient pathway which harvests energy where energy transfer first evolved transfer energy from organic molecules to ATP still is starting point for ALL cellular respiration –but it’s inefficient generate only 2 ATP for every 1 glucose –occurs in cytosol

12 intermembrane space inner membrane outer membrane matrix cristae Mitochondria — Structure Double membrane energy harvesting organelle –smooth outer membrane –highly folded inner membrane cristae –intermembrane space fluid-filled space between membranes –matrix inner fluid-filled space –DNA, ribosomes –enzymes free in matrix & membrane-bound mitochondrial DNA What cells would have a lot of mitochondria?

13 Mitochondria – Function What does this tell us about the evolution of eukaryotes? Endosymbiosis! Dividing mitochondria Who else divides like that? Advantage of highly folded inner membrane? More surface area for membrane- bound enzymes & permeases Membrane-bound proteins Enzymes & permeases bacteria!

14 pyruvate    acetyl CoA + CO 2 Oxidation of pyruvate NAD 3C2C 1C [ 2x ] Pyruvate enters mitochondrial matrix –3 step oxidation process –releases 2 CO 2 (count the carbons!) –reduces 2 NAD  2 NADH (moves e - ) –produces 2 acetyl CoA Acetyl CoA enters Krebs cycle Where does the CO 2 go? Exhale!

15 14 3. Krebs Cycle -oxidizes the acetyl Co-A -occurs in the matrix of the mitochondria

16 15 Krebs Cycle After glycolysis, pyruvate oxidation, and the Krebs cycle, glucose has been oxidized to: - 6 CO ATP - 10 NADH - 2 FADH 2 These electron carriers proceed to the electron transport chain.

17 Electron Transport Chain –series of proteins built into inner mitochondrial membrane –yields ~36 ATP from 1 glucose! –only in presence of O 2 (aerobic respiration) O2O2 That sounds more like it!

18 NAD + Q C NADH H 2 O H+H+ e–e– 2H + +O2O2 H+H+ H+H+ e–e– FADH NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex FAD e–e– Electron carriers pass electrons & H + to ETC –H cleaved off NADH & FADH 2 –electrons stripped from H atoms  H + (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ETC) flowing electrons = energy to do work –transport proteins in membrane pump H + (protons) across inner membrane to intermembrane space H+H+ H+H+ H+H+

19 H+H+ ADP + P i H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP Chemiosmosis: Set up a H + gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + P i  ATP “proton-motive” force

20 H+H+ H+H+ O2O2 + Q C ATP Pyruvate from cytoplasm Electron transport system ATP synthase H2OH2O CO 2 Krebs cycle Intermembrane space Inner mitochondrial membrane 1. Electrons are harvested and carried to the transport system. 2. Electrons provide energy to pump protons across the membrane. 3. Oxygen joins with protons to form water. 2H + NADH Acetyl-CoA FADH 2 ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. Mitochondrial matrix 2 1 H+H+ H+H+ O2O2 H+H+ e-e- e-e- e-e- e-e- ATP

21 Cellular respiration 2 ATP ~36 ATP ++ ~40 ATP

22 21 Oxidation Without O 2 Respiration occurs without O 2 via either: 1. anaerobic respiration -methanogens (CO 2  CH 4 ) -sulfur bacteria (SO 4  H2 S ) 2. fermentation -ethanol (yeast) -lactic acid (animal cells)

23 Pyruvate is a branching point Pyruvate O2O2 O2O2 mitochondria Krebs cycle aerobic respiration fermentation anaerobic respiration

24 Fermentation (anaerobic) Bacteria, yeast 1C 3C2C pyruvate  ethanol + CO 2  Animals, some fungi pyruvate  lactic acid 3C  beer, wine, bread  cheese, anaerobic exercise (no O 2 ) NADHNAD + NADHNAD + back to glycolysis 

25 24 Catabolism of Protein & Fat In the absence of carbohydrates, animals can break down other molecules: -proteins: amino acids converted to a molecule that enters glycolysis or the Krebs cycle -fats: fatty acids enter Krebs cycle (produces more energy than glucose)

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