Oxidation and Reduction Reactions Electron transfer from an electron donor to an electron acceptor simultaneously Cells use electron carriers to carry electrons (often in H atoms) Two important electron carriers Nicotinamide adenine dinucleotide (NAD+) 3 ATP per Molecule Flavine adenine dinucleotide (FAD) → FADH2 2 ATP Per Molecule © 2012 Pearson Education Inc. 1

Figure 5.2 Oxidation-reduction, or redox, reactions Electron donor Oxidized donor Electron acceptor Reduced acceptor Oxidation

Carbohydrate Catabolism Many organisms oxidize carbohydrates as primary energy source Remove electrons Glucose most commonly used Glucose catabolized by two processes: cellular respiration and fermentation © 2012 Pearson Education Inc. 3

Figure 5.12 Summary of glucose catabolism Respiration G L Y C O L Y S I S Glucose Fermentation 2 Pyruvic acid Pyruvic acid (or derivative) Formation of fermentation end-products Acetyl-CoA KREBS CYCLE ELECTRON TRANSPORT Electrons

Carbohydrate Catabolism Glycolysis Overview Occurs in cytoplasm of most cells Involves splitting of a six-carbon glucose into two three-carbon sugar molecules Net gain of two ATP molecules Two molecules of NADH Precursor metabolite pyruvic acid © 2012 Pearson Education Inc. 5

Carbohydrate Catabolism Glycolysis Divided into three stages involving 10 total steps Energy-investment stage 2 ATP are used to phosphorylate glucose Lysis stage Fructose, 1,6-bipohsphate is cleaved Energy-conserving stage Pyruvic acid is produced 4 ATP are produced 2 NADH are produced © 2012 Pearson Education Inc. 6

Figure 5.13 Glycolysis-overview

Carbohydrate Catabolism Cellular Respiration Resultant pyruvic acid completely oxidized to produce ATP by series of redox reactions Three stages of cellular respiration 1. Synthesis of acetyl-CoA 2. Krebs cycle 3. Final series of redox reactions (electron transport chain) © 2012 Pearson Education Inc. 8

Carbohydrate Catabolism Cellular Respiration 1) Synthesis of acetyl-CoA Pyruvic acid is converted into acetyl-coenzyme A (acetyl-CoA) Happens to both pyruvic acid molecules 2 molecules of acetyl-CoA 2 molecules of CO2 2 molecules of NADH Cytoplasm © 2012 Pearson Education Inc. 9

Figure 5.15 Formation of acetyl-CoA Respiration Fermentation Pyruvic acid Decarboxylation Acetate Coenzyme A Acetyl-coenzyme A (acetyl-CoA)

Carbohydrate Catabolism Cellular Respiration 2) The Krebs cycle Great amount of energy remains in bonds of acetyl-CoA Transfers much of this energy to coenzymes NAD+ and FAD Occurs in cytosol of prokaryotes and in matrix of mitochondria in eukaryotes © 2012 Pearson Education Inc. 11

Figure 5.16 The Krebs cycle Acetyl-CoA OOH OOH OOH OOH Respiration Fermentation Acetyl-CoA OOH OOH OOH OOH Oxaloacetic acid OOH Citric acid OOH OOH OOH Malic acid OOH OOH Isocitric acid KREBS CYCLE OOH HOO Fumaric acid OOH OOH -Ketoglutaric acid OOH OOH OOH Succinic acid Succinyl-CoA

Carbohydrate Catabolism Cellular Respiration The Krebs cycle Results in Two molecules of ATP Two molecules of FADH2 Six molecules of NADH Four molecules of CO2 © 2012 Pearson Education Inc. 13

Carbohydrate Catabolism Cellular Respiration 3) Electron transport Chain Most significant ATP production Carrier molecules pass electrons from one to another to final electron acceptor Energy from electrons used to pump protons (H+) across the membrane, establishing a proton gradient Located in cristae of eukaryotes and in cytoplasmic membrane of prokaryotes © 2012 Pearson Education Inc. 14

Figure 5.17 An electron transport chain Respiration Fermentation Path of electrons Reduced FMN Oxidized Oxidized FeS Reduced Reduced CoQ Oxidized 2 Oxidized Cyt Reduced Reduced Cyt Oxidized 2 Oxidized Cyt Reduced 2 2 Final electron acceptor

Carbohydrate Catabolism Cellular Respiration Electron transport Four categories of carrier molecules Flavoproteins- NADH enters here Ubiquinones- FADH2 enters here Metal-containing proteins Cytochromes Aerobic respiration: oxygen serves as final electron acceptor © 2012 Pearson Education Inc. 16

Electron transport chain Figure 6.11a Space between membranes H H H H H H H H Electron carrier H H H H H Protein complex Inner mitochondrial membrane – – FADH2 FAD H Electron flow 1 2 O2 2 H H2O – – Figure 6.11 How electron transport drives ATP synthase machines (part 1) NADH NAD ADP P ATP H H H H H Matrix Electron transport chain ATP synthase

Figure 5.18 One possible arrangement of an electron transport chain Bacterium Mitochondrion Intermembrane space Matrix Exterior Cytoplasmic membrane Cytoplasm Exterior of prokaryote or intermembrane space of mitochondrion FMN Ubiquinone Cyt b Phospholipid membrane Cyt a3 Cyt c Cyt a NADH from glycolysis, Krebs cycle, pentose phosphate pathway, and Entner-Doudoroff pathway Cyt c2 FADH2 from Krebs cycle ATP synthase Cytoplasm of prokaryote or matrix of mitochondrion

Carbohydrate Catabolism Cellular Respiration Summary In glycolysis and the Krebs cycle Electrons are taken from glucose and transferred to NADH and FADH2 NADH and FADH2 pass their electron to the ETC As the electron move down the chain, proton pumps use energy to move protons across the membrane Creating a proton gradient © 2012 Pearson Education Inc. 19

Carbohydrate Catabolism Cellular Respiration Chemiosmosis Use of electrochemical (ion) gradients to generate ATP Create proton gradient from energy released in redox reactions of ETC “Water held behind a dam” Protons flow down electrochemical gradient through ATP synthases that phosphorylate ADP to ATP © 2012 Pearson Education Inc. 20

Carbohydrate Catabolism Cellular Respiration Chemiosmosis Pumps three protons per NADH 3 ATP per NADH 30 ATP Pumps two protons per FADH2 FADH2 delivers electrons further down the chain Transfers 1/3 fewer protons 2 ATP per FADH2 4 ATP 34 ATP from ECT © 2012 Pearson Education Inc. 21

Carbohydrate Catabolism Cellular Respiration Glycolysis- net 2 ATP Krebs cycle- 2 ATP ETC- 34 ATP 38 ATP total © 2012 Pearson Education Inc. 22

Respiration Review https://www.youtube.com/watch?v=-Gb2EzF_XqA

Practice Label the diagram of respiration with the proper terms.

Carbohydrate Catabolism Fermentation Sometimes cells cannot completely oxidize glucose by cellular respiration Cells require constant source of NAD+ Cannot be obtained simply using glycolysis and Krebs cycle Fermentation pathways provide cells with source of NAD+ Uses organic molecule within cell as final electron acceptor © 2012 Pearson Education Inc. 25

Carbohydrate Catabolism Fermentation Any spoilage of food by microorganisms Any process that produces alcoholic beverages or acidic dairy products Scientific definition: Releases energy from oxidation of organic molecules Does not require oxygen Does not use the Krebs cycle or ETC Uses an organic molecule as the final electron acceptor © 2012 Pearson Education Inc. 26

Carbohydrate Catabolism Fermentation Allows ATP production to continue in the absence of cellular respiration Not as efficient as cellular respiration Most of the energy remains in the bonds of the fermentation product Products include: ethanol and lactic acid Fermentation can be used to identify mos Proteus ferment lactose E. coli ferments glucose and lactose © 2012 Pearson Education Inc. 27

Carbohydrate Catabolism Fermentation Contains single carbohydrate and a source of protein Used to identify what carbon source a microbe can use If sugar is used, acidic end products and gas are produced pH indicator changes color © 2012 Pearson Education Inc. 28

Figure 5.21 Fermentation Pyruvic acid Lactic acid Acetaldehyde Ethanol Respiration Fermentation Pyruvic acid Lactic acid Acetaldehyde Ethanol

Figure 5.22 Representative fermentation products and the organisms that produce them Glucose Pyruvic acid Aspergillus Lactobacillus Streptococcus Organisms Propionibacterium Saccharomyces Clostridium Fermentation CO2, propionic acid Lactic acid CO2, ethanol Acetone, isopropanol Fermentation products Swiss cheese Cheddar cheese, yogurt, soy sauce Wine, beer Nail polis remover, rubbing alcohol