Chapter 9 CELLULAR RESPIRATION Relationship of Processes Cellular - PDF document

7/29/2016 Chapter 9 CELLULAR RESPIRATION Relationship of Processes Cellular Respiration complex process whereby cells make ATP by breaking down organic compounds(glucose) Respiration: exergonic (releases E) many rxns in aerobic respiration are redox: (one C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + ATP (+ heat) reactant is oxidized while another is reduced) location: mitochondrial cristae Photosynthesis: endergonic (requires E) 6H 2 O + 6CO 2 + Light  C 6 H 12 O 6 + 6O 2 Oxidation and Reduction Glucose Catabolism Catabolic Pathway Complex organic Simpler waste molecules products with less E Some E used to do work and dissipated as heat Oxygen is extremely electronegative loses e- (donor) Oxidation of glucose transfers e- to lower energy state- does main work of respiration releases energy to make ATP ** done in series of steps** gains e- (acceptor) Not all electrons are transferred from one substance to another, some change the degree of e- sharing in covalent bonds. 1

7/29/2016 Moving Electrons NAD+ • Coenzyme (nicotinamide adenine dinucleotide) Electrons cannot move alone in cells • Electron acceptor- carries electrons to ETC • Move as part of H atom • Acts as an oxidizing agent during respiration • Energy is released as electrons “fall” from organic • Dehydroginase(enzyme)- catalyzes NAD+  NADH molecule to O2. Electron Carriers • Move electrons by shuttling H atoms around NAD+  NADH FAD+2  FADH2 NAD animation Electron Transport Chain • ETC breaks the fall of electrons of oxidation of glucose into series of smaller steps • Released energy is used to make ATP • Extra energy is released as heat. Glycolysis Overview Glycolysis (glucose/splitting) Stage 1: Energy Investment • Cell uses ATP to phosphorylate glucose GLUCOSE(6C)is partially oxidized • Endergonic end products: 2 PYRUVATE(3C), 2 NADH, 2 ATP Stage 2: Energy Payoff • Two 3-C compounds oxidized • Exergonic - occurs in cytosol - 1 st step: always occurs before Yield respiration or fermentation 2 pyruvate - occurs in the absence of oxygen 2 NADH - ancient pathway (early prokaryotes) 2 ATP- substrate-level phosphorylation - inefficient - Phosphate comes from sugar substrate(PEP), not ETC 2

7/29/2016 Steps of Glycolysis 2 Possible Pathways for Pyruvate If O2 present If no O2 present respiration fermentation (aerobic) (anaerobic respiration) mitochondria cytosol glycolysis animation Cellular Respiration(aerobic) Stages of Cellular Respiration C 6 H 12 O 6 + 6 O 2  6 H 2 O + 6 CO 2 + 32 ATP Process of breakdown of pyruvate in the 1. Glycolysis presence of oxygen 2. Citric Acid(Krebs)Cycle 3. Oxidative Phosphorylation - prokaryotic cells: occurs in cytosol - eukaryotic cells: occurs in mitochondria - much more efficient than anaerobic respiration 2 Major Stages of Respiration Location of Processes Citric Acid Cycle (matrix) 1. Citric Acid Cycle ETC - oxidation of glucose is completed (inner - NADH and FADH2 are produced membrane of cristae) 2. Electron transport chain - NADH is used to make ATP via oxidative phosphorolation - location where most ATP is made 3

7/29/2016 Pyruvate oxidized to Acetyl CoA Citric Acid Cycle (Krebs Cycle) 2 pyruvate from glycolysis enter cycle Occurs before the Citric Acid Cycle Occurs in mitochondrial matrix Glucose is fully oxidized • 3 step oxidation process • NAD+ reduced to NADH (acetate formed) • Coenzyme A attached to acetate to form Acetyl CoA • CO2 by-product is released into atmosphere Pyruvate + CoA + NAD+  Acetyl CoA + CO2 + NADH Oxidative Phosphorylation ( production of ATP) Electron Transport Chemiosmosis Chain • H+ ions pumped across • Occurs in inner membrane inner mitochondrial of mitochondria membrane • Produces ATP by • H+ ions diffuse through oxidative ATP synthase to make phosphorylation via ATP chemiosmosis animation Oxidative Phosphorylation Electron Transport Chain • Collection of molecules embedded in inner membrane of mitochondria • Tightly bound protein complexes • FADH2 and NADH donate e- for electron transport (redox rxns) for ATP synthesis • Does not make ATP directly, ATP made through chemiosmosis • O2 is final e- acceptor from H+ to form H2O 4

7/29/2016 Energy Coupling of Chemiosmosis How ATP Synthase Works • H+ ions enter stator (1/2 channel) in membrane • H+ ions enter rotor- changes shape of subunits – Rotor spins within membrane • Each H+ ion makes one complete turn – Passes into matrix • Turning of rod produces ATP from ADP and Pi animation ETC Fermentation = glycolysis + regeneration of NAD + 1. Lactate Fermentation (animals) 2. Alcoholic Fermentation NO ATP FORMED IN - pyruvate converted to lactate ( yeasts, plant cells, microorganisms) - pyruvate converted to ethanol FERMENTATION A. NADH is oxidized and donates its H to pyruvate A. CO2 molecule is removed from pyruvate (3C) forming acetaldehyde B. resultant NAD returns to glycolysis (2 C) where it is reduced to NADH PURPOSE OF FERMENTATION: B. acetyldehyde is reduced to form TO REGENERATE NAD FOR GLYCOLYSIS ethanol C no release of CO2 2 H (from NADH + H ion) are added to 2C compound to form ethanol 2 ATP produce enough energy for prokaryotes and small ** 2 ATP formed ** multi-cellular eukaryotes C. NAD is formed (back to glycolysis) ** process is CYCLICAL** ** 2 ATP formed ** Useful for anaerobes and facultative anaerobes **lactate eventually diffuses into liver ** process is CYCLICAL** where it is converted back to pyruvate when O2 again present ** Very widespread metabolic pathway of Earth’s organisms **causes alcohol in beer and wine, air bubbles in bread, beer, and wine** Alternative Energy Sources Alternative Energy Sources What if the body runs out of sugar for Fats as fuel: glycolysis? Can the body still make ATP? • Glycerol  PGAL  glycolysis • FA tails  Acetyl CoA  Krebs YES Proteins as fuel: • proteins  amino acids This is how the Atkins and South Beach diets • Amino acids  pyruvate or work. acetyl CoA  Krebs They are low carb, high protein/fat diets. 5

7/29/2016 Biofeedback Regulation of Cellular Respiration Importance of Phosphofructokinase: (regulates rate of respiration) • Allosteric enzyme- receptors for specific inhibitors and activators • controls rate of glycolysis and citric acid cycle • Inhibited by ATP and citrate review animation citrate citric acid cycle ATP glycolysis • Stimulated by AMP • AMP+ P + P  ATP Review of Respiration Glycolysis Citric Acid Cycle Oxidative Phosphorylation Electron Transport Chain Chemiosmosis 6