R1CellRespire - Cellular Respiration Cellular Respiration...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Cellular Respiration Cellular Respiration & Metabolism Metabolism Metabolic Pathways: a summary Bioenergetics • Flow of energy in living systems obeys: • 1st law of thermodynamics: – Energy can be transformed, but it cannot be created or destroyed. • 2nd law of thermodynamics: – Energy transformations increase entropy (degree of disorganization of a system). – Only free energy (energy in organized state) can be used to do work. Coupled Reactions: Bioenergetics • Energy transfer from one molecule to another couples chemical reactions • Exergonic reaction: reaction releases energy • Endergonic reaction: reaction requires energy • Coupled bioenergetic reactions: the energy released by the exergonic reaction is used to power the endergonic reaction. • Systems tend to go from states of higher free energy to states of lower free energy. Coupled Pathways: Bioenergetics • Energy transfer from one metabolic pathway to another by means of ATP. • Catabolic pathway (catabolism): breaking down of macromolecules. Releases energy which may be used to produce ATP. • Anabolic pathway (anabolism): building up of macromolecules. Requires energy from ATP. • Metabolism: the balance of catabolism and anabolism in the body. Heyer Cellular Respiration: ATP is the cell’s rechargable battery • Breaking down complex glucose molecule releases energy. • That energy is used to convert ADP into ATP. ADP + P + energy —› ATP • Energy is released as ATP breaks down into ADP and AMP. ATP —› energy + ADP + P 1 Cellular Respiration Forward reaction is exergonic Back reaction is endergonic Coupled Metabolic Pathways: via ATP • Cells use ATP by breaking phosphate bond and transferring energy to other compounds • Cells make ATP by transferring energy from other compounds to form phosphate bond Cellular Metabolism ATP drives endergonic reactions • The three types of cellular work a re powered by the hydrolysis of ATP • Cellular Respiration provides ATP • Cellular “Work” requires ATP P i P Motor protein (a) Protein moved Mechanical work : ATP phosphorylates motor proteins Membrane protein ADP + ATP P P Solute (b ) Solute transported P NH 3 Reactants: Glutamic acid and ammonia (c) i i Transport work : ATP phosphorylates transport proteins Glu + Figure 8.11 P NH 2 Glu + P i Product (glutamine) made Chemical work : ATP phosphorylates key reactants Exergonic Oxidation of Organic Fuel Coupled reactions using ATP. Heyer • Controlled oxidation releases energy in small, usable increments • Redox reactions regulated through reducing and oxidizing agents 2 Cellular Respiration Coupled Reactions: Redox Transfer of electrons is called oxidation-reduction • AKA, a redox process Reduction–oxidation [“Redox”] The Hindenburg explosion: Respiration: a redox process is oxidized C6H1206 + 6 O2 Ë 6 H20 + 6 CO2 An exergonic redox reaction 2 H2+O2 2 H2O is reduced ∆G= –686 kcal/mol; \ exergonic & spontaneous So how does the cell prevent spontaneous combustion? • Keep the oxidation reactions and reduction reactions separate! But the reduction of oxygen drives the oxidation of sugar!? • Couple them by means of electron shuttles . Coenzymes: Electron Carriers Oxidation-Reduction (continued) • NAD+ (nicotinamide adenine dinucleotide) – {Derived from vitamin B3: niacin} NAD+ + H+ + 2e- ¤ NADH • FADH+ (flavin adenine dinucleotide) – {Derived from vitamin B2: riboflavin} FADH+ + H+ + 2e- ¤ FADH2 • Reminder: Hydrogen = H+ + e- Heyer 3 Cellular Respiration Respiration Cellular Respiration v Respiration is a redox process. • Controlled oxidation of organic fuel (exergonic) v Respiration uses a proton gradient to power ATP synthesis. – coupled with • Phosphorylation of ADP to ATP (endergonic) Preview v An electron transport chain links the oxidation of food molecules to the production of the proton gradient. Respiration mechanisms v Harvesting electrons from food: glycolysis & the Krebs cycle. v Making a proton gradient: electron transport chain. v Using the proton gradient to power ATP synthesis: chemiosmosis & oxidative phosphorylation. Respiration hexokinase Getting started q“Light the match” ß Spend an ATP to phorhorylate glucose ß “activated glucose” qGlucose gate is not permeable to glucose-6-phosphate ß Glucose trapped in cell Heyer Cellular Respiration (making ATP) “sugar splitting ” 1 C 6 glucose Ø 2 C 3 pyruvates 4 Cellular Respiration Glycolysis summary Glycolysis v “Light two matches” to get started v Glucose partially ozixidized. v Electrons harvested, ATP made. v Pyruvate is end product. Anaerobic Respiration Pyruvate Reduction Anaerobic Respiration = “fermentation” Pyruvate Reduction Fermentation pathways regenerate NAD + & dispose of pyruvate. lactate fermentation Heyer alcohol fermentation 5 Cellular Respiration Aerobic Respiration OXIDIZED COENZYMES Glycolysis can lead to respiration or fermentation REDUCED COENZYMES OXIDIZED COENZYMES REDUCED COENZYMES Pyruvate transport & oxidation to acetate Pyruvate / H+ symporter Proton gradient drives cotransport of pyruvate & H+ into matrix Pyruvate H+ cytosol Aerobic Respiration intermembrane space mitochondrial matrix Krebs Cycle •Acetate completely oxidized to CO 2 •For each acetate through the cycle: • 3 (NAD +)Æ 3 (NADH+H+) • 1 FAD Æ 1 FADH 2 • 1 ADP Æ 1ATP •(Remember, 1 glucose produced 2 acetates) Heyer 6 Cellular Respiration Aerobic Respiration Krebs Cycle (Citric Acid Cycle) (Tricarboxylic Acid [TCA] Cycle) Carboxylic acid and keto acid intermediates Respiration mechanisms Intermembrane space v Harvesting electrons from food: glycolysis & the Krebs cycle. Matrix v Making a proton gradient: electron transport chain. v Using the proton gradient to power ATP synthesis: chemiosmosis & oxidative phosphorylation. Oxidative phosphorylation: 2 parts proton gradient powers ATP synthesis pumping protons H+ high energy H+ + H H+ + H H+ H+ H+ H+ H+ + H H+ + +H H Heyer e- H+ e- lower energy H+ proton e- electron H+ ATP H+ + H H+ + H ADP + P i H+ + H+ H H+ H+ + H H+ + +H H Inner membrane Outer membrane Electron Transport Chain v Series of increasingly electronegative ecarriers. v NADH starts at high energy level, FADH2 slightly lower. v O2 is the final eacceptor. 7 Cellular Respiration Electron Transport Chain Electron transport chain & oxidative phosphorylation v Each complex transports 1 proton for each pair of e-. v e- from NADH pump 3 H+, e- from FADH2 pump only 2. Respiration mechanisms v Harvesting electrons from food: glycolysis & the Krebs cycle. v Making a proton gradient: electron transport chain. v Using the proton gradient to power ATP synthesis: chemiosmosis & oxidative phosphorylation. ATP Synthase v ATP synthase couples facilitated diffusion of H+ with ATP formation. Heyer ATP Synthase: Facilitated diffusion powers ADP phosphorylation ATP Synthase v Proton gradient is electrochemical. v As protons move through ATP synthase, they turn the rotor. v Active sites on knob change shape, causing ADP phosphorylation. 8 Cellular Respiration Review Yield from the electron transport chain v Each NADH (2 e-) pumps 10 H+. v Each FADH2 pumps 6-7 H+. v 3-4 H+ Ë 1 ATP. v 1 glucose: 10 NADH Ë 25-33 ATP. 2 FADH2 Ë 3-4 ATP. about 32-34 ATP v Plus the 4 ATP from glycolysis & TCA cycle = 34–38 ATP/glucose How much ATP would you have to eat? Aerobic Respiration v 1 mole glucose Ë 32 moles ATP. v Glucose: 180 g/mole v ATP: 507 g/mole v 25 g glucose = 2.3 kg ATP Cellular Respiration Fig. 6.16 • Anaerobic Respiration “without air ” • Aerobic Respiration “with air ” • Produces much more ATP per sugar molecule Non-toxic waste product (CO2) • Produce ATP in absence of O 2 = glycolysis + pyruvate oxidation + Krebs cycle + electron transport system Allows use of fats and protein for fuel = glycolysis + pyruvate reduction • • • • * { PGAL = 3PG } Heyer 9 ...
View Full Document

This note was uploaded on 09/02/2011 for the course BIOL 6B taught by Professor Heyer during the Spring '10 term at DeAnza College.

Ask a homework question - tutors are online