© 2014 Pearson Education, Inc. Figure 7.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2  H 2 O Cellular respiration in mitochondria Organic molecules  O2 O2 ATP ATP powers most cellular work Heat energy Get used to this picture….

© 2014 Pearson Education, Inc. Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 or 2 NADH Glycolysis Glucose 2 Pyruvate oxidation 2 Acetyl CoA Citric acid cycle 6 NADH2 FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis  about 26 or 28 ATP  2 ATP About 30 or 32 ATP Maximum per glucose: MITOCHONDRION Aerobic Respiration overview Can you draw this process? Can you explain it?

Fermentation & anaerobic respiration enable cells to produce ATP without the use of oxygen  Most cellular respiration requires O 2 to produce ATP  Without O 2, the electron transport chain will cease to operate  In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP © 2014 Pearson Education, Inc.

 Anaerobic respiration:  uses an electron transport chain with a final electron acceptor other than O 2, for example, sulfate (S has a similar electronegativity to O)  Fermentation:  uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2014 Pearson Education, Inc.

Figure 7.17 Glucose CYTOSOL Glycolysis Pyruvate O 2 present: Aerobic cellular respiration No O 2 present: Fermentation Ethanol, lactate, or other products Acetyl CoA Citric acid cycle MITOCHONDRION

© 2014 Pearson Education, Inc. Alcohol fermentation Lactic acid fermentation 2 ADP  2 2 ATP P i Glucose Glycolysis 2 Pyruvate 2 CO 2 2 NADH  2 H  2 NAD  2 Ethanol 2 Acetaldehyde 2 Lactate 2 NADH  2 H  2 NAD  2 Pyruvate Glycolysis 2 ATP 2 ADP  2 P i Glucose PathwayAlcoholLactic Acid SubstratePyruvate ProductsCO 2, NAD +, EtOHNAD +, lactate ExamplesBrewing, breadmakingYogurt, cheese, muscle cells

Comparing Fermentation with Anaerobic and Aerobic Respiration © 2014 Pearson Education, Inc. AerobicAnaerobicFermentation Products of glycolysis Pyruvate 2 ATP (net) NAD+ > NADH Pyruvate 2 ATP (net) NAD+ > NADH Pyruvate 2 ATP (net) NAD+ > NADH CO2 Final Electron Acceptor O 2 Not O 2, example SO 4 Pyruvate, acetaldehyde # ATP produced during respiration 32 Includes Krebs & Glycolysis contribution 32 (I think) 2, that’s all you get Other products CO 2 H 2 O H 2 S Lactic Acid Ethanol

Comparing Fermentation with Anaerobic and Aerobic Respiration  All use glycolysis (net ATP  2) to oxidize glucose and harvest chemical energy of food  In all three, NAD  is the oxidizing agent that accepts electrons during glycolysis  The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O 2 in cellular respiration  Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule © 2014 Pearson Education, Inc.

 Obligate anaerobes carry out only fermentation or anaerobic respiration and cannot survive in the presence of O 2  Facultative anaerobes: can survive using either fermentation or cellular respiration  In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes © 2014 Pearson Education, Inc.