BO101 2024 Cell Biology - Cellular Respiration PDF

Cellular respiration BO101 - Cell Biology - Lecture 6 Dr Andrew Flaus, Biochemistry Energy ow in ecosystems plants, algae all eukaryotes Campbell g 10.1 fi fl Stages of cellular respiration...

Cellular respiration BO101 - Cell Biology - Lecture 6 Dr Andrew Flaus, Biochemistry Energy ow in ecosystems plants, algae all eukaryotes Campbell g 10.1 fi fl Stages of cellular respiration Campbell g 10.5 fi Glycolysis: from glucose to pyruvate ๏ Occurs in cytoplasm ‣ Eukaryotes and prokaryotes ๏ In ‣ 1 x glucose ๏ Out ‣ 2 x pyruvate (aka pyruvic acid) ‣ 2 x NADH ‣ 2 x ATP 2x Campbell g 10.7 fi Pyruvate oxidation to acetyl CoA ๏ In mitochondrial matrix ‣ Pyruvate transport from cytosol ๏ Pyruvate dehydrogenase ‣ Oxidation reaction NAD+ gains 2 electrons ‣ Pyruvate → CO2 + acetyl ๏ acetyl CoA ‣ Acetyl attached to Coenzyme A Campbell gs 7.17, 10.9 fi Citric acid cycle = TCA, Krebs cycle ๏ Citric acid cycle aka ‣ TCA cycle (tricarboxylic acid) ‣ Krebs cycle ๏ In mitochondrial matrix ๏ Breakdown of acetyl group ‣ 2 x CO2 ‣ 1 x ATP ๏ Electron transfers ‣ 3 x NADH, 1 x FADH2 Campbell g 10.10 fi Outtputs of aerobic respiration NADH Stage Metabolic transformation ATP FADH2 CO2 Glucose → Glycolysis 2 x pyruvate + e- 2 2 - Pyruvate 2 x pyruvate → oxidation acetyl CoA + CO2 + e- - 2 2 2 x acetyl CoA → Citric acid cycle 2 x CO2 + e- 2 8 4 Oxidative phosphorylation O2 + e- → H2O 26-28 -12 - Total Glucose + O2 → CO2 + H2O ~32 0 6 Stages of cellular respiration Campbell g 10.5 fi Aerobic respiration oxidises glucose Redox reactions oxidation = loss of electrons reduction = gain of electrons Campbell chapter 10 Aerobic respiration is stepwise Glucose donates electrons, becomes oxidised NAD+ accepts electrons, becomes reduced Campbell chapter 10 Nicotinamide adenine dinucleotide (NAD) ๏ NAD acts as electron carrier ‣ Receives electrons from glycolysis, pyruvate oxidation, TCA cycle NAD+ is reduced to NADH ‣ Gets re-oxidised to NAD+ by electron transport chain Campbell g 10.3 fi Electron transport chain in respiration ๏ Re-oxidation of NADH ‣ Electrons from glucose are transferred to NAD+ ➔ NADH ‣ Electron transport chain moves electrons from NADH to O2 ‣ O2 is reduced to H2O ๏ Free energy is released to ATP using e- transfer ‣ Mechanism uses a proton gradient and chemiosmosis ๏ Process is called oxidative phosphorylation Campbell g 10.4 fi Process of oxidative phosphorylation Campbell g 10.14 fi Electron transport chain intermembrane ๏ In inner mitochondrial space membrane ๏ Electrons from NADH pass via chain of proteins ‣ Eventually deposited on O2 to generate H2O ๏ Protons get moved across membrane during process ‣ Creates proton gradient across matrix inner mitochondrial membrane Campbell g 10.14 fi ATP synthase generates ATP ๏ ATP synthase enzyme ๏ Protons pass back through enzyme to generate ATP ‣ Osmosis = balances concentration ‣ Proton passage drives rotor Proton-motive force ‣ Rotation is used to catalyse ADP phosphorylation to ATP ๏ Energy transformation ‣ Potential > mechanical > chemical ‣ “Chemiosmosis” Campbell g 10.13 fi Outputs of aerobic respiration NADH Stage Metabolic transformation ATP FADH2 CO2 Glucose → Glycolysis 2 x pyruvate + e- 2 2 - Pyruvate 2 x pyruvate → oxidation acetyl CoA + CO2 + e- - 2 2 2 x acetyl CoA → Citric acid cycle 2 x CO2 + e- 2 8 4 Oxidative phosphorylation O2 + e- → H2O 26-28 -12 - Total Glucose + O2 → CO2 + H2O ~32 0 6 Other catabolites feed into pathway ๏ Many molecules can feed into cellular respiration ‣ Proteins ‣ Carbohydrates ‣ Fats ๏ Major catabolic pathway for energy production Campbell g 10.18 fi Fermentation when oxygen is limiting Fermentation ๏ Fermentation ‣ “Catabolic process that makes limited ATP without electron transport chain, and produces characteristic end product” ๏ No oxygen as electron acceptor ‣ NAD needs to be re-oxidised ‣ Use pyruvate as alternative ‣ End product can be lactic acid, or ethanol and CO2 Campbell g 10.17 fi  Fermentation ๏ No oxygen as electron acceptor ‣ NAD needs to be re-oxidised ‣ Use pyruvate as alternative ๏ End products ‣ Lactic acid bacteria Pyruvate reduced to lactic acid Acidi es environment ‣ Yeasts Pyruvate reduced to ethanol + CO2 Useful for … Campbell g 10.17 fi fi Summary of lecture ๏ Glycolysis ๏ Pyruvate oxidation ‣ Redox processes ๏ TCA cycle ๏ Oxidative phosphorylation ‣ NADH re-oxidation to NAD+ ‣ Electron transport chain ‣ Chemiosmosis and ATP synthase ๏ Fermentation ‣ End products lactate, CO2, ethanol Learning outcomes of lecture On successful completion of this lecture, you will be able to: ‣ Outline the stages of cellular respiration and account for the main inputs and outputs ‣ Describe the overall processes occurring during glycolysis, pyruvate oxidation and the citric acid cycle ‣ Explain the principle of redox reduction-oxidation reactions ‣ Place oxidative phosphorylation in context as the major energy yielding catabolic process in the cell ‣ Locate the reactions of oxidative phosphorylation within the cell ‣ Explain how the electron transport chain generates both water and a proton motive force to drive ATP Synthase ‣ Describe how anaerobic respiration yields end products such as lactic acid, CO2 and ethanol that have traditional uses in biotechnology