Chapter9 - Make-up exam this Thursday Oct 8 at 5:40 PM in...

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: Make-up exam this Thursday, Oct. 8 at 5:40 PM in Heldenfels 100. Heldenfels No class next Tuesday, Oct. 13. Light energy Energy flow in Energy living systems living Plants and some Plants bacteria use energy from the sun to reduce CO2 by reduce adding electrons to it from water. This reduced carbon is then oxidized back to CO2 and back water to release energy for growth and maintenance of cells and organisms. cells ECOSYSTEM Photosynthesis in chloroplasts CO2 + H2O Cellular respiration in mitochondria Organic +O molecules 2 ATP ATP powers most cellular work Heat energy In redox reactions, electrons are transferred to more In electronegative atoms. Formation of this more stable arrangement, where electrons are held very tightly, releases energy. where becomes oxidized (loses electron) becomes reduced (gains electron) Oxidization of methane as a simple example Reactants becomes oxidized Products becomes reduced Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water In aerobic organisms, oxidation of glucose provides In abundant energy, enough to make about 36 molecules of ATP for every molecule of glucose. ATP becomes oxidized becomes reduced (36-38 ATPs) Lots of energy is released by the reduction of O2 to H2O. Lots Lots of energy is released by the reduction of O2 to H2O H2 + 1/2 O2 + 2H (from food via NADH) Controlled release of + – 2H + 2e energy for synthesis of ATP ATP por trans tron Elec chain 1 /2 O2 Free energy, G Explosive release of heat and light energy Free energy, G ATP ATP 2 e– 1 t 2H + /2 O2 H2O H2O (a) Uncontrolled reaction (b) Cellular respiration Oxidation of glucose takes place in several small steps, Oxidation allowing the cell to capture the energy for further use. allowing NAD+ is usually the electron carrier that stores this energy. Dehydrogenase Fig. 9-4 – + – + + NADH Dehydrogenase Reduction of NAD+ Oxidation of NADH Nicotinamide (reduced form) Nicotinamide (oxidized form) 2e +2H 2e +H + NAD+ + 2[H] + H Structure of Nicotinamide Structure Adenine Dinucleotide and its mechanism for storing electrons mechanism H The first step in the oxidation of glucose is glycolysis, which The occurs in the cytoplasm and releases only a little energy. occurs Electrons carried via NADH Glycolysis Glucose Pyruvate Cytosol ATP Substrate-level phosphorylation Know what goes into Know glycolysis and what comes out of it! comes In glycolysis, ATP is formed by substrate-level In phosphorylation, where a high-energy phosphate bond is transferred directly to ADP from an enzyme’s substrate. transferred Enzyme ADP P Substrate Product + ATP Enzyme Oxidation of glucose is completed by the Citric Acid Cycle in the Oxidation matrix of mitochondria. Energy released is stored on the electron carriers NADH and FADH2 carriers Electrons carried via NADH Electrons carried via NADH and FADH2 Glycolysis Glucose Pyruvate Citric acid cycle Mitochondrion Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation Know what goes Know in and what comes out comes Energy from NADH and FADH2 is converted to ATP through oxidative Energy phosphorylation, which occurs on the inner mitochondrial membrane. phosphorylation, Electrons carried via NADH Electrons carried via NADH and FADH2 Glycolysis Glucose Pyruvate Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Mitochondrion Cytosol ATP Substrate-level phosphorylation ATP Substrate-level phosphorylation ATP Oxidative phosphorylation Energy investment phase Overview of Overview Glycolysis Glycolysis Glucose 2 ADP + 2 P 2 ATP used Know what Know goes in and what comes out. what Energy payoff phase 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+ 2 Pyruvate + 2 H2O Net Glucose 4 ATP formed – 2 ATP used 2 NAD+ + 4 e– + 4 H+ 2 Pyruvate + 2 H2O 2 ATP 2 NADH + 2 H+ The first few The stages of glycolysis require the input of energy. energy. Glucose ATP 1 Hexokinase ADP Glucose Glucose-6-phosphate ATP 1 Hexokinase ADP Glucose-6-phosphate Fig. 9-9-2 Glucose ATP 1 Hexokinase ADP Glucose-6-phosphate 2 Phosphoglucoisomerase Glucose-6phosphate Fructose-6-phosphate 2 Phosphoglucoisomerase Fructose-6-phosphate Fructose 1,6bisphosphate bisphosphate is an unstable molecule with lots of energy. Why? Why? Glucose ATP 1 Hexokinase ADP Fructose-6-phosphate Glucose-6-phosphate 2 Phosphoglucoisomerase ATP 3 Fructose-6-phosphate ATP 3 Phosphofructokinase ADP Phosphofructokinase ADP Fructose1, 6-bisphosphate Fructose1, 6-bisphosphate Fig. 9-9-4 Glucose Aldolase splits F1,6-PP into 2 three carbon Aldolase molecules molecules ATP 1 Hexokinase ADP Glucose-6-phosphate 2 Phosphoglucoisomerase Fructose1, 6-bisphosphate 4 Fructose-6-phosphate Aldolase ATP 3 Phosphofructokinase ADP 5 Isomerase Fructose1, 6-bisphosphate 4 Aldolase 5 Isomerase Dihydroxyacetone phosphate Glyceraldehyde3-phosphate Glyceraldehyde3-phosphate Dihydroxyacetone phosphate 2 NAD+ 6 Triose phosphate dehydrogenase 2P i Enzymatic Enzymatic reactions of these 3-C compounds releases 4 molecules of ATP and two molecules of NADH for each glucose. each Each NADH Each is equal to ~3 ATPs. ATPs. 2 NADH + 2 H+ 2 1, 3-Bisphosphoglycerate 2 ADP 7 Phosphoglycerokinase 2 ATP 2 2 3-Phosphoglycerate Phosphoenolpyruvate 2 ADP 8 Phosphoglyceromutase 2 ATP 2 2-Phosphoglycerate 10 Pyruvate kinase 9 2 H2O Enolase 2 Phosphoenolpyruvate 2 ADP 10 Pyruvate kinase 2 ATP 2 Pyruvate 2 Pyruvate Pyruvate, one end product of glycolysis, is transported into Pyruvate, mitochondria where one of its carbons is immediately oxidized to CO2. The remaining 2 carbons are attached to oxidized The the Coenzyme A carrier molecule. CYTOSOL NAD+ 2 MITOCHONDRION NADH + H+ 1 Pyruvate Transport protein CO 2 3 Coenzyme A Acetyl CoA The remaining 2 The carbon atoms from pyruvate, attached to CoA, enter the citric acid cycle and are completely oxidized to CO2. to Pyruvate NAD NADH + H+ Acetyl CoA CoA CoA CO2 + CoA Energy from these oxidizations is captured on the ecarriers NADH and FADH2. FADH Citric acid cycle FADH2 FAD ADP + P i ATP 2 CO2 3 NAD+ 3 NADH + 3 H+ This figure is too This detailed for our purposes, but once again, you should know what goes into the citric acid cycle and what comes out. H2 O Acetyl CoA CoA— SH NADH +H+ NAD+ 8 1 H2 O Oxaloacetate 2 Malate Citrate Isocitrate Citric acid cycle 3 NAD+ NADH + H+ 7 CO 2 CoA— SH Fumarate 6 CoA— SH 4 α -Ketoglutarate FADH2 FAD 5 NAD+ CO 2 Succinate GTP GDP ADP ATP Pi Succinyl CoA NADH + H+ INTERMEMBRANE SPACE The ATP synthase works The as a rotorary motor. as H+ Rotor Stator Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX This energy is used to pump protons against their electrochemical gradient. This Protons flow back into the matrix through ATP synthase. The energy dissipated through this process is used to synthesize ATP. dissipated H+ H H+ Protein complex of electron carriers Q Ι ΙΙ FADH2 NADH (carrying electrons from food) NAD+ ΙΙΙ + Cyt c H+ ΙV ATP synthase 2 H+ + 1/2O2 H2O ADP + P i H+ ATP FAD 1 Electron transport chain 2 Chemiosmosis Oxidative phosphorylation Free energy (G) relative to O2 (kcal/mol) High energy electrons are High passed from NADH and FADH2 down an e- transport FADH chain of increasing electronegativity until they reach O2, the final e- acceptor. reach NADH 50 2 e– NAD+ FADH2 2 e– 40 FMN Fe•S Q Ι FAD Fe•S Ι Ι Cyt b 30 Fe•S Cyt c1 Cyt c Cyt a 20 Cyt a3 IV ΙΙ Ι FAD Multiprotein complexes The reduced oxygen then The picks up protons from solution to become H2O. solution 10 2 e– (from NADH or FADH2) Massive amounts of energy Massive are released during electron transport. transport. 0 2 H+ + 1/2 O 2 H2 O This is a great summary figure. Study it well. CYTOSOL Electron shuttles span membrane 2 NADH or 2 FADH2 2 NADH 6 NADH MITOCHONDRION 2 NADH 2 FADH2 Glycolysis Glucose 2 Pyruvat e 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis + 2 ATP + 2 ATP + about 32 or 34 ATP Maximum per glucose: About 36 or 38 ATP What happens What if there is no O2 if to use as an eacceptor? acceptor? Fermentation! The main point The of fermentation is not to make beer. It is to regenerate NAD+ so glycolysis can continue continue 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 Pyruvate 2 NAD+ 2 NADH + 2 H+ 2 CO2 2 Ethanol (a) Alcohol fermentation 2 Acetaldehyde Mammalian cells Mammalian can also ferment, at least for a little while. while. 2 ADP + 2 P i 2 ATP Glucose Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate (b) Lactic acid fermentation The presence of O2 determines whether aerobic respiration or anaerobic fermentation occurs. anaerobic CYTOSOL Glucose Glycolysis Pyruvate No O2 present: Fermentation O2 present: Aerobic cellular respiration MITOCHONDRION Ethanol or lactate Acetyl CoA Citric acid cycle Protein s Carbohydrates Fats Although we Although focused on glucose in class, most other food molecules feed into aerobic respiration at some point along the way. NH3 Amino acids Sugars Glycerol Fatty acids Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation Glucose AMP Stimulates + – Fructose-1,6-bisphosphate Inhibits Inhibits Respiration is controlled Respiration by feedback inhibition. If your body has enough ATP, then the process stops and excess food molecules are stored as glycogen or fat. glycogen Glycolysis Fructose-6-phosphate Phosphofructokinase – Pyruvate ATP Acetyl CoA Citrate Citric acid cycle Oxidative phosphorylation Fig. 9-UN5 Inputs and Outputs for Glycolysis Inputs Outputs 2 + 2 NADH ATP Glycolysis Glucose 2 Pyruvate Fig. 9-UN6 Inputs and Outputs for the Citric Acid Cycle Inputs S—CoA C CH3 2 Acetyl CoA 6 NADH O C CH2 COO 2 Oxaloacetate COO Citric acid cycle 2 FADH2 O 2 Outputs ATP This diagram omits CO2 as an output, but it is very important! For oxidative phosphorylation, For inputs are electrons from NADH and FADH2 and oxygen (as the terminal electron acceptor). INTERMEMBRANE SPACE H+ Outputs are reduced oxygen (water) and a proton gradient across the inner mitochondrial membrane, which is used to drive the synthesis of ATP. drive ATP synthase ADP + P i MITOCHONDRIAL MATRIX H+ ATP ...
View Full Document

This note was uploaded on 01/27/2011 for the course BIOL 112 taught by Professor Vaughn during the Fall '08 term at Texas A&M.

Ask a homework question - tutors are online