Cellular Respiration Sylvia S. Mader BIOLOGY Chapter 8: pp. 133-149 10th Edition Chapter 8: pp. 133-149 Cellular Respiration Sylvia S. Mader Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Insert figure 8.2 here NADH e– NADH e– e– e– Cytoplasm NADH and e– F ADH 2 Mitochondrion e– e– Glycolysis Preparatory reaction cycle Citric acid Electron transport chain and chemiosmosis glucose pyruvate 2 ADP 2 ADP 4 ADP 4 ATP total 2 ATP net gain 2 ADP 2 ATP 32 ADP or 34 32 or 34 ATP 1 PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display

Connection between Photosynthesis and Respiration Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Fermentation = anaerobic Cellular respiration = aerobic STAGES OF CELLULAR RESPIRATION AND FERMENTATION Fermentation = anaerobic Cellular respiration = aerobic Cellular respiration oxidizes sugar and produces ATP in 3-4 main stages: Glycolysis, Prep (Transition) Stage, Kreb’s (Citric Acid) Cycle, ETC Fermentation oxidizes sugar and does not produce ATP, but yields a constant supply of NAD+ (an electron carrier) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Glucose Breakdown: Summary Reaction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Oxidation C6H12O6 + 6O2 6CO2 + 6H2O + energy glucose Reduction Electrons are removed from substrates and received by oxygen, which combines with H+ to become water. Glucose is oxidized and O2 is reduced 4

NAD+ and FAD NAD+ (nicotinamide adenine dinucleotide) Called a coenzyme of oxidation-reduction. It can: Oxidize a metabolite by accepting electrons Reduce a metabolite by giving up electrons Each NAD+ molecule used over and over again FAD (flavin adenine dinucleotide) Also a coenzyme of oxidation-reduction Sometimes used instead of NAD+ Accepts two electrons and two hydrogen ions (H+) to become FADH2 5

Cellular Respiration 6 O f r o m a i r H2O O2 and glucose enter cells, Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O 2 f r o m a i r H2O O2 and glucose enter cells, which release H2O and CO2. CO2 g l u c o s e f r o m intermembrane space cristae Mitochondria use energy from glucose to form ATP from ADP + P . ADP + P ATP © E. & P. Bauer/zefa/Corbis; (Bread, wine, cheese, p. 139): © The McGraw Hill Companies, Inc./John Thoeming, photographer; (Yogurt, p. 139): © The McGraw Hill Companies, Inc./Bruce M. Johnson, photographer 6

ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Phases of Cellular Respiration Cellular respiration includes four phases: Glycolysis is the breakdown of glucose into two molecules of pyruvate Occurs in cytoplasm ATP is formed Does not utilize oxygen Transition (preparatory) reaction Both pyruvates are oxidized and enter mitochondria Electron energy is stored in NADH Two carbons are released as CO2 (one from each pyruvate) 7

Phases of Cellular Respiration Citric acid cycle Occurs in the matrix of the mitochondrion and produces NADH and FADH2 In series of reaction releases 4 carbons as CO2 Turns twice (once for each pyruvate) Produces two immediate ATP molecules per glucose molecule Electron transport chain Extracts energy from NADH & FADH2 Passes electrons from higher to lower energy states Produces 32 molecules of ATP 8

Glucose Breakdown: Overview of 4 Phases Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display e– NADH NADH e– e– e– NADH and FADH2 Cytoplasm e– Mitochondrion e– e– Glycolysis Electron transport chain and chemiosmosis Preparatory reaction Citric acid cycle glucose pyruvate 2 ATP 2 ATP 4 ADP 4 ATP total 2 ATP net gain 2 AD P 2 ATP 32 ADP or 34 32 or 34 ATP 9

Glucose Breakdown: Glycolysis Occurs in cytoplasm outside mitochondria Energy Investment Steps: Two ATP are used to activate glucose Glucose splits into two G3P molecules Energy Harvesting Steps: Oxidation of G3P occurs by removal of electrons and hydrogen ions Two electrons and one hydrogen ion are accepted by NAD+ resulting two NADH Four ATP produced by phosphorylation Net gain of two ATP Both G3Ps converted to pyruvates 10

First phase in aerobic respiration is GLYCOLYSIS… First phase in aerobic respiration is GLYCOLYSIS….no oxygen involved in this phase Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Mitochondrion Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

PREPARATORY PHASE (energy investment) Steps – A fuel molecule is energized, using ATP. Glucose 1 3 Details of glycolysis... ...Do we need to know that??!! Step 1 Glucose-6-phosphate 2 Fructose-6-phosphate 3 Fructose-1,6-diphosphate Step A six-carbon intermediate splits into two three-carbon intermediates. 4 4 Glyceraldehyde-3-phosphate (G3P) ENERGY PAYOFF PHASE 5 Step A redox reaction generates NADH. 5 1,3-Diphosphoglyceric acid (2 molecules) 6 Steps – ATP and pyruvic acid are produced. 3-Phosphoglyceric acid (2 molecules) 6 9 7 2-Phosphoglyceric acid (2 molecules) 8 2-Phosphoglyceric acid (2 molecules) 9 Pyruvic acid Figure 6.9B (2 molecules per glucose molecule) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

GLYCOLYSIS BASICS http://highered. mcgraw-hill Glucose Pyruvic acid Figure 6.9A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Glycolysis: Inputs and Outputs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Glycolysis inputs outputs glucose 2 pyruvate 2 NAD+ 2 NADH 2 ATP 2 ADP 4 ADP + 4 P 4 ATP total 2 ATP net gain 11

Pyruvate Pyruvate is a pivotal metabolite in cellular respiration If O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm. During fermentation, glucose is incompletely metabolized to lactate, or to CO2 and alcohol (depending on the organism). If O2 is available to the cell, pyruvate enters mitochondria by aerobic process. 16

Fermentation An anaerobic process that reduces pyruvate to either lactate or alcohol and CO2 NADH passes its electrons to pyruvate Alcoholic fermentation, carried out by yeasts, produces carbon dioxide and ethyl alcohol Used in the production of alcoholic spirits and breads. Lactic acid fermentation, carried out by certain bacteria and fungi, produces lactic acid (lactate) Used commercially in the production of cheese, yogurt, and sauerkraut. Other bacteria produce chemicals anaerobically, including isopropanol, butyric acid, proprionic acid, and acetic acid. 17

Fermentation is an anaerobic alternative to aerobic respiration Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP But a cell must have a way of replenishing NAD+ Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

ALCOHOLIC FERMENTATION In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol This recycles NAD+ to keep glycolysis working released GLYCOLYSIS 2 Pyruvic acid 2 Ethanol Glucose Figure 6.15A Figure 6.15C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

LACTIC ACID FERMENTATION In lactic acid fermentation, pyruvic acid is converted to lactic acid As in alcoholic fermentation, NAD+ is recycled Lactic acid fermentation is used to make cheese and yogurt GLYCOLYSIS 2 Pyruvic acid 2 Lactic acid Glucose Figure 6.15B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Efficiency of Fermentation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fermentation inputs outputs glucose 2 lactate or 2 alcohol and 2 CO2 2 ADP + 2 P 2 ATP net gain 25

Acetyl CoA (acetyl coenzyme A) Pyruvic acid is chemically groomed for the Krebs cycle in the Transition or Prep Stage Each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl group, which enters the Krebs cycle Pyruvic acid Acetyl CoA (acetyl coenzyme A) CO2c Figure 6.10 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Aerobic Respiration Continues in the Mitochondria ATP Substrate-level phosphorylation Mitochondrion Glycolsis Glucose Pyruvate Citric acid cycle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Alpha-ketoglutaric acid Details of the Kreb’s Cycle……. Do we need to know all that???? Answer: Yes and No 2 carbons enter cycle Oxaloacetic acid 1 Citric acid CO2 leaves cycle 5 KREBS CYCLE 2 Malic acid 4 Alpha-ketoglutaric acid 3 CO2 leaves cycle Succinic acid Step Acetyl CoA stokes the furnace Steps and NADH, ATP, and CO2 are generated during redox reactions. Steps and Redox reactions generate FADH2 and NADH. 1 2 3 4 5 Figure 6.11B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Let’s look at a simplified version of the Kreb’s Cycle first….. The Krebs cycle completes the oxidation of glucose, generating many NADH and FADH2 molecules Acetyl CoA The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group What are the products of the Kreb’s cycle? 2 KREBS CYCLE CO2 Figure 6.11A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

KREB’S CYCLE aka Citric Acid Cycle……. times 2…. WHY. http://highered Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Oxidative Phosphorylation = ETC plus Chemiosmosis Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Chemiosmosis powers most ATP production http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_2_.html The electrons from NADH and FADH2 travel down the electron transport chain (slowly losing energy). They will be grabbed by oxygen Energy released by the electrons is used to pump H+ into the space between the mitochondrial membranes In chemiosmosis, the H+ ions diffuse back through the inner membrane through ATP synthase complexes, which capture the energy to make ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Electron transport chain Therefore, the two mechanisms that generate ATP are ETC and Chemiosmosis Cells use the energy released by “falling” electrons to pump H+ ions across a membrane The energy of the gradient is harnessed to make ATP by the process of chemiosmosis High H+ concentration ATP synthase uses graient energy to make ATP Membrane Electron transport chain ATP synthase Energy from Low H+ concentration Figure 6.7A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Overview of Cellular Respiration (Aerobic) 6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS Cells use many kinds of organic molecules as fuel for cellular respiration Polysaccharides can be hydrolyzed to monosaccharides and then converted to glucose for glycolysis Proteins can be digested to amino acids, which are chemically altered and then used in the Krebs cycle Fats are broken up and fed into glycolysis and the Krebs cycle Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Pathways of molecular breakdown Food, such as peanuts Polyscaccharides Fats Proteins Sugars Glycerol Fatty acids Amino acids Amino groups Pyruvic acid ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Glucose G3P Acetyl CoA KREBS CYCLE GLYCOLYSIS Figure 6.16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

The fuel for respiration ultimately comes from photosynthesis All organisms have the ability to harvest energy from organic molecules Plants, but not animals, can also make these molecules from inorganic sources by the process of photosynthesis (Chapter 7) Figure 6.18 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings