* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Electron transport chains
Fatty acid synthesis wikipedia , lookup
Lactate dehydrogenase wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Metalloprotein wikipedia , lookup
Butyric acid wikipedia , lookup
Mitochondrion wikipedia , lookup
Phosphorylation wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Photosynthesis wikipedia , lookup
Nicotinamide adenine dinucleotide wikipedia , lookup
NADH:ubiquinone oxidoreductase (H+-translocating) wikipedia , lookup
Photosynthetic reaction centre wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Biochemistry wikipedia , lookup
Electron transport chain wikipedia , lookup
Microbial metabolism wikipedia , lookup
Light-dependent reactions wikipedia , lookup
Ch 9 Cellular Respiration Harvesting Chemical Energy Section 9.1 Catabolic pathways yield energy by oxidizing organic fuels Principles of Energy Harvest Catabolic pathways: • Fermentation • Cellular Respiration C6H12O6 + 6O2 ---> 6CO2 + 6H2O + E (ATP + heat) Redox reactions • Oxidation-reduction • OIL RIG (adding e- reduces + charge) • Oxidation is e- loss; reduction is egain • Reducing agent: e- donor • Oxidizing agent: e- acceptor Oxidizing agent in respiration • NAD+ (nicotinamide adenine dinucleotide) • Removes electrons from food (series of reactions) • NAD + is reduced to NADH • Enzyme action: dehydrogenase • Oxygen is the eventual eacceptor Electron transport chains • Electron carrier molecules (membrane proteins) • Shuttles electrons that release energy used to make ATP • Sequence of reactions that prevents energy release in 1 explosive step • Electron route: food---> NADH electron transport chain ---> oxygen Cellular respiration • Glycolysis: cytosol; degrades glucose into pyruvate • Kreb’s Cycle (Citric Acid Cycle): mitochondrial matrix; pyruvate into carbon dioxide • Electron Transport Chain (Oxidative Phophorylation): inner membrane of mitochondrion; electrons passed to oxygen Section 9.2 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Glycolysis • 1 Glucose ---> 2 pyruvate molecules • Energy investment phase: cell uses ATP to phosphorylate fuel • Energy payoff phase: ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by food oxidation • Net energy yield per glucose molecule: 2 ATP plus 2 NADH; no CO2 is released; occurs aerobically or anaerobically Glycolysis • Overview of Glycolysis by the Khan Academy Section 9.3 The Citric acid cycle completes the energy-yielding oxidation of organic molecules • In the presence of O2, pyruvate enters the mitochondrion • Enters via active transport , with the help of a transport protein • Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links the cycle to glycolysis • The citric acid cycle, also called the Krebs cycle, takes place within the mitochondrial matrix • The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH2 per turn Kreb’s Cycle • Each pyruvate is converted into acetyl CoA: CO2 is released; NAD+ ---> NADH; coenzyme A, makes molecule very reactive • From this point, each turn 2 C atoms enter (pyruvate) and 2 exit (carbon dioxide) • Oxaloacetate is regenerated (the “cycle”) • For each pyruvate that enters: 3 NAD+ reduced to NADH 1 FAD+ reduced to FADH2 1 ATP molecule • The citric acid cycle has eight steps, each catalyzed by a specific enzyme • The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate • The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle • The NADH and FADH2 produced by the cycle relay electrons extracted from food to the electron transport chain Kreb’s Cycle Kreb’s Cycle animation Section 9.4 During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis • Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food • These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation • The electron transport chain is in the cristae of the mitochondrion • Most of the chain’s components are proteins, which exist in multiprotein complexes • The carriers alternate reduced and oxidized states as they accept and donate electrons • Electrons drop in free energy as they go down the chain and are finally passed to O2, forming H2O Electron transport chain • Cytochromes carry electron carrier molecules (NADH & FADH2) down to oxygen • Chemiosmosis: energy coupling mechanism • ATP synthase: • produces ATP by using the H+ gradient (proton-motive force) pumped into the inner membrane space from the electron transport chain; this enzyme harnesses the flow of H+ back into the matrix to phosphorylate ADP to ATP (oxidative phosphorylation) • The electron transport chain generates no ATP • The chain’s function is to break the large free-energy drop from food to O2 into smaller steps that release energy in manageable amounts Fig. 9-16 H+ H+ H+ H+ Protein complex of electron carriers Cyt c V Q ATP synthase FADH2 NADH 2 H+ + 1/2O2 H2O FAD NAD+ ADP + P i (carrying electrons from food) ATP H+ 1 Electron transport chain Oxidative phosphorylation 2 Chemiosmosis Electron Transport • Cellular respiration video Review: Cellular Respiration • • Glycolysis: 2 ATP (substrate-level phosphorylation) • Kreb’s Cycle: 2 ATP (substrate-level phosphorylation) • • • • • Electron transport & oxidative phosphorylation: 2 NADH (glycolysis) = 6ATP 2 NADH (acetyl CoA) = 6ATP 6 NADH (Kreb’s) = 18 ATP 2 FADH2 (Kreb’s) = 4 ATP • 38 TOTAL ATP/glucose Section 9.5 Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen • Most cellular respiration requires O2 to produce ATP • Glycolysis can produce ATP with or without O2 (in aerobic or anaerobic conditions) • In the absence of O2, glycolysis couples with fermentation or anaerobic respiration to produce ATP • Anaerobic respiration uses an electron transport chain with an electron acceptor other than O2, for example sulfate • Fermentation uses phosphorylation instead of an electron transport chain to generate ATP • Fermentation consists of glycolysis plus reactions that regenerate NAD+, which can be reused by glycolysis • Two types: 1. alcohol fermentation 2. lactic acid fermentation Alcohol Fermentation • pyruvate is converted to ethanol • Occurs in 2 steps, first step releases CO2 • Alcohol fermentation by yeast is used in brewing, winemaking, and baking 2 ADP + 2 Pi 2 ATP Fig. 9-18 Glucose Glycolysis 2 Pyruvate 2 NAD+ 2 NADH + 2 H+ 2 CO2 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 Pi Glucose 2 ATP Glycolysis 2 NAD+ 2 NADH + 2 H+ 2 Pyruvate 2 Lactate (b) Lactic acid fermentation Lactic Acid Fermentation • pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2 • Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt • Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce Fermentation and Aerobic Respiration Compared • Both use glycolysis to oxidize glucose and other organic fuels to pyruvate • They have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration • Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule Obligate anaerobes • carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 Facultative anaerobes • Yeast and many bacteria • they can survive using either fermentation or cellular respiration Section 9.6 Glycolysis and the citric acid cycle connect to many other metabolic pathways