Chemotrophic Energy Metabolism - Cellular Respiration PDF

Chemotrophic energy metabolism – Cellular Respiration Course Outcome 6  CHEMOTROPHIC ENERGY METABOLISM involves reactions and pathways by which cells catabolize nutrients and conserve ATP. Some of the chemical energy is released in this breakdown cells make use of th...

Chemotrophic energy metabolism – Cellular Respiration Course Outcome 6  CHEMOTROPHIC ENERGY METABOLISM involves reactions and pathways by which cells catabolize nutrients and conserve ATP. Some of the chemical energy is released in this breakdown cells make use of the food we eat to meet energy needs CATABOLIC (exergonic)  Oxidation NADH NAD+ Oxidation is the loss of electrons, Loss of Hydrogen atoms, or gain of oxygen NADH = Nicotinamide Adenine Dinucleotide reduced NAD = Nicotinamide Adenine Dinucleotide  Reduction Fe+3 Fe+2 NAD+ NADH Reduction is the Gain of electrons, Gain of Hydrogen atoms, or loss of oxygen atoms  Oxidation-Reduction reaction: coupled Oxidizing agent (Oxidized substrate/reactant) Gains electron and becomes reduced R + NADH RH + NAD+ Reducing agent (Reduced substrate/reactant) Loses electron and becomes oxidized  Reactants Products becomes oxidized becomes reduced Methane Oxygen Carbon dioxide Water (reducing (oxidizing agent) agent)  Oxidizing Reducing agent agent Causes the Causes the oxidation of reduction of FUNCTION another another substrate substrate BEFORE THE Oxidized Reduced REACTION Substrate Substrate DURING THE Gains electron Loses electrons REACTION AFTER THE is reduced is oxidized  Oxidation cannot occur without reduction, and vice versa. The reducing agent becomes oxidized, and the oxidizing agent becomes reduced.  Cellular Respiration Reducing agent (Reduced substrate/reactant) Loses electron and becomes oxidized Oxidizing agent (Oxidized substrate/reactant) Gains electron and becomes reduced  CHEMOTROPHS energy released from oxidation serves as primary energy source CHEMOORGANOTROPH CHEMOLITHOTROPHS S obtain energy from the obtain energy from the oxidation of electron donor oxidation of electron donor molecules that are organic molecules that are compounds inorganic compounds Inorganic molecules: may Organic molecules: C-H contain C but not bonded to H  CHEMOTROPHS molecules (chemicals) as energy source undergo cellular respiration (exergonic) Source: From Campbell Biology, 10th ed. By J. B. Reece, L. A. Urry, M. L. Cain, S. A. Wasserman, P. V. Minorsky, and R. B. Jackson, 2014, Pearson  ENERGY FLOW AND CHEMICAL CYCLING IN ECOSYSTEMS Energy arrives in an ecosystems as solar energy and used by phototrophs for photosynthesis. Energy exits the ecosystem as heat. Image Source: From Campbell Essential Biology, 5th ed. by E. J. Simon, J. L. Dickey, & J. B. Reece, 2013, Pearson CELLULAR RESPIRATION OF CHEMOTROPHS AEROBIC ANAEROBIC CELLULAR CELLULAR RESPIRATION RESPIRATION process of generating process of generating energy in the presence energy without of oxygen oxygen Source: From Campbell Biology, 10th ed. By J. B. Reece, L. A. Urry, M. L. Cain, S. A. Wasserman, P. V. Minorsky, and R. B. Jackson, 2014, Pearson  CELLULAR RESPIRATION It is a catabolic and exergonic process by which the chemical energy of food molecules is released and used to produce ATP and water. 15  CELLULAR RESPIRATION CHEMICAL ENERGY FROM CELLULAR RESPIRATION (glucose) 17  Hydrolysis and Synthesis of ATP High Acid Anhydride Bond Energ y Bond Energy is release d How do cells break down glucose? 19  Glycolysis Main Glycolytic Pathway Embden-Meyerhof-Parnas Pathway (cytoplasm- Prokaryotic cell, Eukaryotic cell)  GLYCOLYSIS It is a process that occurs in the cytoplasm. A glucose molecule is broken into two molecules of pyruvate (three-carbon compound). ATP is produced from ADP and inorganic phosphate. Nicotinamide adenine dinucleotide (NAD+) is reduced to form NADH. 21 22 Aerobic Respiration Overview Substrate-Level Phosphorylation 24  Glycolysis Main Glycolytic Pathway Embden-Meyerhof-Parnas Pathway (cytoplasm- Prokaryotic cell, Eukaryotic cell) Hexokinase Hexokinase Phosphoglucoisomeras e Hexokinase Phosphofructokinase Aldolase Triose phosphate isomerase Glyceraldehyde-3- phosphate dehydrogenase 1,3- bisphosphoglycera te Phosphoglycerokinas e 3-phosphoglycerate Phosphoglyceromutas e Enolase Pyruvate Kinase SUMMARY OF GLYCOLYSIS 35 Fate of Pyruvate Release of CO2 and Acetyl CoA Slide 36 Fate of Pyruvate Depends on oxygen availability and on the species of the organism When oxygen is present, pyruvate is oxidized to acetyl coenzyme A (acetyl-CoA) which enters the citric acid cycle. Aerobic respiration. Without oxygen, pyruvate is reduced in order to oxidize N ADH back to NAD+ Fermentation. 37 PYRUVATE PROCESSING Release of CO2 and Acetyl CoA Slide 38  PYRUVATE PROCESSING In the presence of oxygen, pyruvate is oxidized Occurs in mitochondria in eukaryotes. Multienzyme complex called pyruvate dehydrogenase catalyzes the reaction. Occurs at the plasma membrane in prokaryotes. 39  PYRUVATE PROCESSING A sequence of reactions occur inside the enzyme complex called pyruvate dehydrogenase. One carbon of each pyruvate molecule is oxidized to CO2. During this process, NAD is reduced to NADH. The remaining two-carbon acetyl unit in each pyruvate molecule reactions with the compound coenzyme A to form Acetyl coenzyme A. For every 2 pyruvate molecules from glycolysis, 2 molecules each of CO2 and Acetyl CoA are produced. 40 CITRIC ACID CYCLE Oxidizing Acetyl CoA to CO2 Slide 41  CITRIC ACID CYCLE Tricarboxylic Acid (TCA) or Krebs Cycle The starting molecule is a citrate (three carboxyl groups). 8-step cycle in the mitochondrial matrix 42 43 44 45 46 ELECTRON TRANSPORT AND OXIDATIVE PHOSPHORYLATION Building a Proton Gradient to produce ATP Slide 47  H+ H+ H+ H+ Protein complex Cyt c of electron carriers V Q   ATP synthase  2 H+ + 1/2O2 H 2O FADH2 FAD NADH NAD+ ADP + P ATP i (carrying electrons from food) H+ 1 Electron transport chain 2 Chemiosmosis Oxidative phosphorylation  ELECTRON TRANSPORT CHAIN The NADH and FADH2 produced in the previous steps of cellular respiration move through a series of proteins and other molecules that together are called electron transport chain. The oxidation of NADH and FADH2 creates a proton gradient across the membrane of the mitochondria allowing the synthesis of ATP. OXIDATIVE PHOSPHORYLATION A process by which ADP is phosphorylated through the oxidation of NADH and FADH2. 49 What happens when mitochondria pumps out H+ from its matrix to the intermembrane space? PROTON GRADIENT 50  INTERMEMBRANE SPACE H + Stato Rotor r CHEMIOSMOSI S It involves the diffusion of ions, in this case, protons (hydrogen ions) across a Interna membrane. l rod Cata- lytic knob AD P+ P ATP i ATP Synthase MITOCHONDRIAL MATRIX 51  OXIDATIVE PHOSPHORYLATION Six (6) molecules of NADH and two (2) molecules of FADH2 are processed in the electron transport chain and during oxidative phosphorylation. For each NADH processed, 3 molecules of ATP are produced. For each FADH2 processes, 2 molecules of ATP are produced. 52 53 CELLULAR RESPIRATION 38 ATP 54 CELLULAR RESPIRATION AEROBIC ANAEROBIC CELLULAR CELLULAR RESPIRATION RESPIRATION oxygen as final lacks oxygen; uses other final electron electron acceptor acceptor 55 FERMENTATION Emergency back-up pathway to produce ATP Slide 56  FERMENTATION It is a metabolic process that occurs in the cytosol when there is no or not enough oxygen. In this process, an organism converts a carbohydrate into alcohol or an acid. 57  FERMENTATION LACTIC ACID ALCOHOL FERMENTATION FERMENTATION 58 ALCOHOL FERMENTATION Pyruvate from glycolysis is converted to acetaldehyde. Acetaldehyde receives electrons from NADH to form ethanol (waste product). Release of CO2 59  LACTIC ACID FERMENTATION Pyruvate molecules produced from glycolysis receives electrons from NADH to form lactate and NAD+. 60 LACTIC ACID FERMENTATION 61  ALCOHOL FERMENTATION Saccharomyc Baker’s yeast Dough Bread es cerevisiae 62  ALCOHOL BEER MAKING FERMENTATION 63 References Campbell, N., & Reece, J. (2008). Biology (8th ed.). Pearson. Hardin, J., & Bertoni, G. (2018). Becker's World of the Cell (9th ed.). Pearson. Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J., & Duncan, T. (2023). Biology (13th ed.). 2 Penn Plaza, New York: McGraw-Hill. Urry , L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., & Orr , R. B. (2021). Campbell Biology (12th ed.). San Francisco, CA: Pearson Benjamin Cummings. 64