Cellular Respiration and Fermentation

Cellular Respiration and Fermentation
9 Cellular Respiration and Fermentation Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick

Life Is Work Living cells require energy from outside sources
Animals obtain energy by eating plants or feeding on other organisms that eat plants Sunlight (energy)  Ecosystem  Released as Heat Photosynthesis generates O2 and organic molecules Needed for cellular respiration Cells use chemical energy stored in organic molecules to generate ATP ATP powers work

Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic
Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Organic molecules CO2 + H2O + O2 Cellular respiration in mitochondria Figure 9.2 Energy flow and chemical recycling in ecosystems ATP powers most cellular work ATP Heat energy

Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels
Release stored energy by breaking down complex molecules Electron transfer plays a major role in these pathways These processes are central to cellular respiration

Catabolic Pathways and Production of ATP
Breakdown of organic molecules is exergonic Fermentation: Partial degradation of sugars, occurs without O2 Aerobic Respiration: Consumes organic molecules and O2  ATP Anaerobic Respiration: Similar to aerobic respiration, but consumes compounds other than O2 Cellular Respiration: Includes aerobic & anaerobic respiration, often refers to aerobic respiration Carbs, fats, & proteins are all consumed as fuel Cellular respiration occurs with the sugar glucose: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)

Redox Reactions: Oxidation and Reduction
The transfer of electrons during chemical reactions releases energy stored in organic molecules This released energy is used to synthesize ATP

The Principle of Redox Redox Reactions: Chemical reactions that transfer electrons between reactants a.k.a. oxidation-reduction reactions Oxidation: Substance loses electrons, or is oxidized Reduction: Substance gains electrons, or is reduced Amount of + charge is reduced Electron donor is called the reducing agent Electron receptor is called the oxidizing agent Some redox reactions do not transfer electrons Change the electron sharing in covalent bonds EX: Reaction between CH4 and O2

becomes oxidized (loses electron) becomes reduced (gains electron)
Figure 9.UN01 becomes oxidized (loses electron) becomes reduced (gains electron) Figure 9.UN01 In-text figure, NaCl redox reaction, p. 164

Methane (reducing agent) Oxygen (oxidizing agent)
Figure 9.3 Reactants Products becomes oxidized becomes reduced Figure 9.3 Methane combustion as an energy-yielding redox reaction Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water

Oxidation of Organic Fuel Molecules During Cellular Respiration
Fuel (glucose) is oxidized O2 is reduced becomes oxidized becomes reduced Figure 9.UN03 In-text figure, cellular respiration redox reaction, p. 164

Stepwise Energy Harvest via NAD+ and the Electron Transport Chain
Cellular Respiration: Breakdown of glucose and other organic molecules occurs in a series of steps Electrons from organic compounds are transferred to NAD+ (coenzyme) NAD+ (electron acceptor, or carrier): Functions as an oxidizing agent during C.R. Each NADH (reduced form of NAD+) represents stored energy Used to synthesize ATP

2 e− + 2 H+ 2 e− + H+ NAD+ H+ NADH Dehydrogenase Reduction of NAD+
Figure 9.4 2 e− + 2 H+ 2 e− + H+ NAD+ NADH H+ Dehydrogenase Reduction of NAD+ 2[H] (from food) H+ Oxidation of NADH Nicotinamide (oxidized form) Nicotinamide (reduced form) Figure 9.4 NAD+ as an electron shuttle

Dehydrogenase Figure 9.UN04
Figure 9.UN04 In-text figure, dehydrogenase reaction, p. 165

Electron Transport Chain (ETC)
NADH transports the electrons to the ETC ETC passes electrons in a series of steps Highly regulated reaction O2 pulls electrons down the chain in an “energy-yielding tumble” Energy yielded is used to regenerate ATP

Uncontrolled reaction (b) Cellular respiration
Figure 9.5 H2 + ½ O2 2 H + ½ O2 Controlled release of energy 2 H+ + 2 e− ATP ATP Explosive release Electron transport chain Free energy, G Free energy, G ATP 2 e− Figure 9.5 An introduction to electron transport chains ½ O2 2 H+ H2O H2O (a) Uncontrolled reaction (b) Cellular respiration

The Stages of Cellular Respiration: A Preview
Harvesting of energy from glucose has three stages Glycolysis: Breaks down glucose into two molecules of pyruvate (or pyruvic acid) Citric Acid Cycle: Completes breakdown of glucose A.K.A.: Krebs Cycle Oxidative Phosphorylation: Most ATP synthesis A.K.A.: Electron Transport Chain

1. 2. 3. GLYCOLYSIS (color-coded blue throughout the chapter)
Figure 9.UN05 1. GLYCOLYSIS (color-coded blue throughout the chapter) 2. PYRUVATE OXIDATION and the CITRIC ACID CYCLE (color-coded orange) 3. OXIDATIVE PHOSPHORYLATION: Electron transport and chemiosmosis (color-coded purple) Figure 9.UN05 In-text figure, color code for stages of cellular respiration, p. 166

Electrons via NADH Electrons via NADH and FADH2 GLYCOLYSIS PYRUVATE
Figure 9.6-3 Electrons via NADH Electrons via NADH and FADH2 GLYCOLYSIS PYRUVATE OXIDATION OXIDATIVE PHOSPHORYLATION CITRIC ACID CYCLE Glucose Pyruvate Acetyl CoA (Electron transport and chemiosmosis) CYTOSOL MITOCHONDRION Figure An overview of cellular respiration (step 3) ATP ATP ATP Substrate-level Substrate-level Oxidative

Oxidative Phosphorylation
Process that generates most of the ATP Powered by redox reactions Accounts for ~90% of the ATP generated by cellular respiration Small amount of ATP is produced during glycolysis and the citric acid cycle Occurs via substrate-level phosphorylation For each molecule of glucose degraded to CO2 and water, (during cellular respiration), the cell makes up to 32 molecules of ATP

Enzyme Enzyme ADP Substrate ATP Product
Figure 9.7 Enzyme Enzyme ADP P Substrate ATP Figure 9.7 Substrate-level phosphorylation Product

Concept 9.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate
Glycolysis (“sugar splitting”) Breaks down glucose into 2 molecules of pyruvate Occurs in the cytoplasm Has 2 major phases Energy investment phase Energy payoff phase Occurs with or without presence of O2

CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION
Figure 9.UN06 CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION GLYCOLYSIS Figure 9.UN06 In-text figure, mini-map, glycolysis, p. 168 ATP

Energy Investment Phase
Figure 9.8 Energy Investment Phase Glucose 2 ATP used 2 ADP + 2 P Energy Payoff Phase 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e− + 4 H+ 2 NADH + 2 H+ Figure 9.8 The energy input and output of glycolysis 2 Pyruvate + 2 H2O Net Glucose 2 Pyruvate + 2 H2O 4 ATP formed − 2 ATP used 2 ATP 2 2 NAD+ + 4 e− + 4 H+ 2 NADH + 2 H+

GLYCOLYSIS: Energy Investment Phase
Figure 9.9a GLYCOLYSIS: Energy Investment Phase Glyceraldehyde 3-phosphate (G3P) ATP Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate ATP Glucose ADP ADP Isomerase 5 Hexokinase Phosphogluco- isomerase Phospho- fructokinase Aldolase Dihydroxyacetone phosphate (DHAP) 1 4 2 3 Figure 9.9a A closer look at glycolysis (part 1: investment phase)

GLYCOLYSIS: Energy Payoff Phase
Figure 9.9b GLYCOLYSIS: Energy Payoff Phase 2 ATP 2 NADH 2 ATP 2 H2O 2 ADP 2 NAD+ + 2 H+ 2 ADP 2 2 2 2 2 Triose phosphate dehydrogenase Phospho- glycerokinase Phospho- glyceromutase Enolase Pyruvate kinase 2 9 7 8 10 Glycer- aldehyde 3-phosphate (G3P) 6 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Pyruvate Figure 9.9b A closer look at glycolysis (part 2: payoff phase)

Concept 9.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules In the presence of O2, the oxidation of glucose is completed Pyruvate enters mitochondrion (eukaryotic cells) Oxidation of Pyruvate  Acetyl CoA Pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), Links glycolysis to the citric acid cycle This step is carried out by a multienzyme complex that catalyses three reactions

NAD+ NADH + H+ Transport protein
Figure 9.10 MITOCHONDRION CYTOSOL Coenzyme A CO2 1 3 2 Figure 9.10 Oxidation of pyruvate to acetyl CoA, the step before the citric acid cycle NAD+ NADH + H+ Acetyl CoA Pyruvate Transport protein

CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION
Figure 9.UN07 CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION GLYCOLYSIS Figure 9.UN07 In-text figure, mini-map, pyruvate oxidation, p. 169

PYRUVATE OXIDATION CITRIC ACID CYCLE
Figure 9.11 PYRUVATE OXIDATION Pyruvate (from glycolysis, 2 molecules per glucose) CO2 NAD+ CoA NADH + H+ Acetyl CoA CoA CoA CITRIC ACID CYCLE Figure 9.11 An overview of pyruvate oxidation and the citric acid cycle 2 CO2 FADH2 3 NAD+ FAD CoA 3 NADH + 3 H+ ADP + P i ATP

CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION ATP
Figure 9.UN08 CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION GLYCOLYSIS Figure 9.UN08 In-text figure, mini-map, citric acid cycle, p. 171 ATP

The Citric Acid Cycle (A.K.A. Krebs Cycle)
Completes break down of pyruvate  CO2 Cycle oxidizes organic fuel derived from pyruvate Generated each cycle: 1 ATP, 3 NADH, and 1 FADH2 per turn Has 8 steps: catalyzed by a specific enzyme Acetyl group (acetyl CoA) + oxaloacetate  Citrate Next 7 steps decompose citrate  oxaloacetate Thus the process is a cycle Cycle produces NADH & FADH2 Carry electrons (extracted from food) to the ETC

Krebs Cycle Makes an Awesome Comeback!

CITRIC ACID CYCLE Acetyl CoA 1 Oxaloacetate 8 2 Malate Citrate
Figure Acetyl CoA CoA-SH NADH H2O + H+ 1 NAD+ Oxaloacetate 8 2 Malate Citrate Isocitrate CITRIC ACID CYCLE NAD+ NADH 3 7 + H+ H2O CO2 Fumarate CoA-SH -Ketoglutarate Figure A closer look at the citric acid cycle (step 8) 4 6 CoA-SH FADH2 5 CO2 NAD+ FAD Succinate NADH P i + H+ GTP GDP Succinyl CoA ADP ATP

Concept 9.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis After glycolysis and the citric acid cycle: NADH and FADH2 account for most of the energy extracted from food The electron carriers donate electrons to the ETC Powers ATP synthesis via oxidative phosphorylation

The Pathway of Electron Transport
The ETC is in the inner membrane (cristae) of the mitochondrion Most of the chain’s components are proteins Exist in multiprotein complexes Carriers accept and donate electrons  alternate reduced and oxidized states Electrons drop in free energy as they go down the chain Passed to O2, forming H2O

CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION ATP
Figure 9.UN09 CITRIC ACID CYCLE OXIDATIVE PHOSPHORYL- ATION PYRUVATE OXIDATION GLYCOLYSIS Figure 9.UN09 In-text figure, mini-map, oxidative phosphorylation, p. 172 ATP

(originally from NADH or FADH2)
Figure 9.13 NADH 50 2 e− NAD+ FADH2 Multiprotein complexes 2 e− I FAD 40 FMN II Fe•S Fe•S Q III Cyt b 30 Fe•S Cyt c1 Free energy (G) relative to O2 (kcal/mol) IV Cyt c Cyt a Cyt a3 20 Figure 9.13 Free-energy change during electron transport 10 2 e− (originally from NADH or FADH2) 2 H+ + ½ O2 H2O

Electron Transfer and Energy
Electrons transferred from NADH or FADH2  ETC Electrons passed through a number of proteins including cytochromes (each w/Fe atom) to O2 The ETC generates no ATP directly Breaks large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts

Chemiosmosis: Energy-Coupling Mechanism
Electron transfer in ETC  proteins to pump H+ from mitochondrial matrix  intermembrane space Chemiosmosis Use of energy of H+ gradient to drive cellular work ATP Synthase H+ moves back across membrane via protein complex Uses exergonic flow of H+ to drive phosphorylation of ATP

INTERMEMBRANE SPACE Stator H+ Rotor Internal rod Catalytic knob ADP +
Figure 9.14 INTERMEMBRANE SPACE H+ Stator Rotor Internal rod Catalytic knob Figure 9.14 ATP synthase, a molecular mill ADP + P i ATP MITOCHONDRIAL MATRIX

Electron transport chain Chemiosmosis 1 2
Figure 9.15 H+ ATP synthase Protein complex of electron carriers H+ H+ H+ Cyt c IV Q III I II 2 H+ + ½ O2 H2O FADH2 FAD NADH NAD+ Figure 9.15 Chemiosmosis couples the electron transport chain to ATP synthesis ADP + P ATP i (carrying electrons from food) H+ Electron transport chain Chemiosmosis 1 2 Oxidative phosphorylation

Proton-motive Force The H+ gradient H+ gradient Across Membrane
Capacity to do work H+ gradient Across Membrane Energy stored couples the redox reactions of ETC to ATP synthesis

Cellular Respiration: ATP Production
Energy flow during cellular respiration: Glucose  NADH  ETC  proton-motive force  ATP ~34% of the potential energy in 1 glucose molecule is transferred to ATP Produces ~32 ATP Molecules

Electron shuttles span membrane CYTOSOL MITOCHONDRION 2 NADH or
Figure 9.16 Electron shuttles span membrane CYTOSOL MITOCHONDRION 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 GLYCOLYSIS PYRUVATE OXIDATION 2 Acetyl CoA OXIDATIVE PHOSPHORYLATION (Electron transport and chemiosmosis) CITRIC ACID CYCLE Glucose 2 Pyruvate Figure 9.16 ATP yield per molecule of glucose at each stage of cellular respiration + 2 ATP + 2 ATP + about 26 or 28 ATP About 30 or 32 ATP Maximum per glucose:

Concept 9.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen Most cellular respiration requires O2 to produce ATP Absence of O2  ETC will cease to operate Glycolysis couples with anaerobic respiration or fermentation to produce ATP Anaerobic Respiration: Uses an ETC with a final electron acceptor in place of O2, such as sulfate Fermentation: Uses substrate-level phosphorylation to generate ATP, instead of an ETC

Fermentation Consists of glycolysis + reactions that regenerate NAD+
NAD+ can be reused by glycolysis Types of Fermentation: Alcohol Fermentation Lactic Acid Fermentation

Alcohol Fermentation Pyruvate  ethanol
Releases CO2 Produces ethanol Alcohol fermentation by yeast is used in brewing, winemaking, and baking

Lactic acid fermentation
Figure 9.17 2 ADP + 2 P 2 ATP i 2 ADP + 2 P 2 ATP i Glucose GLYCOLYSIS Glucose GLYCOLYSIS 2 Pyruvate 2 NAD+ 2 NADH 2 CO2 2 NAD+ 2 NADH + 2 H+ + 2 H+ 2 Pyruvate Figure 9.17 Fermentation 2 Ethanol 2 Acetaldehyde 2 Lactate (a) Alcohol fermentation (b) Lactic acid fermentation

Lactic Acid Fermentation
Pyruvate reduced by NADH  Lactate NO release of CO2 Some Fungi & Bacteria Used to make cheese and yogurt Human Muscle Cells Used to generate ATP when O2 levels in the blood are too low for aerobic cellular respiration.

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

Mechanisms for Oxidizing NADH
Fermentation Organic molecule acts as a final electron acceptor Pyruvate or Acetaldehyde Produces 2 ATP per glucose molecule Cellular Respiration Electrons are transferred to the ETC Produces 32 ATP per 1 glucose molecule

Anaerobic Organisms Obligate Anaerobes Facultative Anaerobes
Carry out fermentation or anaerobic respiration Cannot survive in the presence of O2 Facultative Anaerobes Can survive using either fermentation or cellular respiration Yeast and many bacteria Pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes

Ethanol, lactate, or other products CITRIC ACID CYCLE
Figure 9.18 Glucose Glycolysis CYTOSOL Pyruvate No O2 present: Fermentation O2 present: Aerobic cellular respiration MITOCHONDRION Ethanol, lactate, or other products Acetyl CoA Figure 9.18 Pyruvate as a key juncture in catabolism CITRIC ACID CYCLE

The Evolutionary Significance of Glycolysis
Glycolysis is a very ancient process Ancient Prokaryotes Thought to have used glycolysis to generate ATP long before there was oxygen in the atmosphere Very little O2 was available in the atmosphere until about 2.7 billion years ago

Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways
Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways

The Versatility of Catabolism
Catabolic Pathways Funnel electrons from many kinds of organic molecules into cellular respiration Glycolysis accepts a wide range of carbohydrates Proteins: Digested to amino acids Amino groups can feed glycolysis, or the citric acid cycle Lipids: Digested to glycerol (used in glycolysis) Fatty Acids: Broken down by beta oxidation and yield acetyl CoA (used in generating acetyl CoA) 1g oxidized fat  >2x ATP as 1g oxidized carbohydrate

Proteins Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids
Figure Proteins Carbohydrates Fats Amino acids Sugars Glycerol Fatty acids GLYCOLYSIS Glucose Glyceraldehyde 3- P NH3 Pyruvate Figure The catabolism of various molecules from food (step 5) Acetyl CoA CITRIC ACID CYCLE OXIDATIVE PHOSPHORYLATION

Biosynthesis (Anabolic Pathways)
Body uses small molecules to build other substances From food From glycolysis From the citric acid cycle

Regulation of Cellular Respiration via Feedback Mechanisms
Feedback Inhibition Most common mechanism for metabolic control ATP concentration drops  Respiration speeds up Plenty of ATP  Respiration slows down Controlling Catabolism Using Enzymes Based mainly on regulating the activity of enzymes at strategic points in the catabolic pathway

Glucose CITRIC ACID CYCLE Oxidative phosphorylation
Figure 9.20 Glucose AMP GLYCOLYSIS Fructose 6-phosphate Stimulates Phosphofructokinase Fructose 1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Citrate Acetyl CoA Figure 9.20 The control of cellular respiration CITRIC ACID CYCLE Oxidative phosphorylation

Figure 9.UN10a Figure 9.UN10a Skills exercise: making a bar graph and evaluating a hypothesis (part 1)

ATP NADH Inputs Outputs GLYCOLYSIS Glucose 2 Pyruvate + 2 + 2
Figure 9.UN11 Inputs Outputs GLYCOLYSIS Glucose 2 Pyruvate ATP + 2 + 2 NADH Figure 9.UN11 Summary of key concepts: glycolysis

Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH CITRIC ACID CYCLE
Figure 9.UN12 Inputs Outputs 2 Pyruvate 2 Acetyl CoA 2 ATP 8 NADH CITRIC ACID CYCLE 2 Oxaloacetate 6 CO2 2 FADH2 Figure 9.UN12 Summary of key concepts: citric acid cycle

Cyt c Q IV III I II INTERMEMBRANE SPACE H+ H+ H+ Protein complex
Figure 9.UN13 INTERMEMBRANE SPACE H+ H+ H+ Cyt c Protein complex of electron carriers IV Q III I Figure 9.UN13 Summary of key concepts: electron transport chain II 2 H+ + ½ O2 H2O FADH2 FAD NADH NAD+ MITOCHONDRIAL MATRIX (carrying electrons from food)

ATP H+ INTER- MEMBRANE SPACE MITOCHON- DRIAL MATRIX ATP synthase ADP +
Figure 9.UN14 INTER- MEMBRANE SPACE H+ MITOCHON- DRIAL MATRIX ATP synthase Figure 9.UN14 Summary of key concepts: ATP synthase ADP + P H+ ATP i

Cellular Respiration and Fermentation

Similar presentations

Presentation on theme: "Cellular Respiration and Fermentation"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Cellular Respiration and Fermentation

Similar presentations

Presentation on theme: "Cellular Respiration and Fermentation"— Presentation transcript:

Similar presentations

About project

Feedback