Respiration Electron Transfer

Respiration Electron Transfer - Respiration: electron...

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Unformatted text preview: Respiration: electron transfer 1 Last Time Enzymes are proteins speed up exergonic chemical reactions Enzyme activity is affected by the cellular environment pH and temperature Regulation of enzyme activity Allosteric inhibition and activation Cooperation binding Feedback 2 Respiration: electron transfer Energy flows through a system Respiration harvesting energy by breaking chemical bonds reduction-oxidation (redox) reactions and electron movement Energy is gathered in steps Glycolysis, Citric Acid Cycle, Oxidative phosphorylation 3 Overview Respiration: Lecture 22: Respiration overview and redox Lecture 23: Glycolysis and citric acid cycle Lecture 24: Oxidative phosphorylation Photosynthesis Lecture 25: Harvesting light energy Lecture 26: Fixing carbon into sugars 4 Fig. 9.2 5 Cellular Respiration: the bottom line Organic compounds + O2 (sugars, fats, protein) CO2 + H2O + energy (ATP and heat) 6 Chemical energy is a type of potential energy Need to access this energy by "breaking down" the molecule C6H12O6 + 6O2 6CO2 + 6H2O + energy (ATP and heat) 7 Respiration is like burning gasoline to run a car.... respiration exergonic reaction connects exergonic rxn to actual work process combustion organic molecules + inorganic molecules + O2 CO2 + H2O O2 CO2 + H2O + energy + energy ATP harvests energy over series of steps drive shaft burns fuel slowly (not all at once) 8 So... ...what does this really mean? .....where is the energy coming from when we break a chemical bond?? exactly can we use this energy? 9 Electrons! C6H12O6 + 6O2 high electrons energy 6CO2 + 6H2O + energy (ATP and heat) low energy - chemical reactions transfer electrons from one reactant to another - in exergonic reactions, electrons will move from a higher energy level to a lower energy level - releasing energy 10 Reduction-oxidation ("redox") reactions transfer of electrons during chemical reactions gaining an electron = reduction losing an electron = oxidation LEO the lion says GER! GER! 11 Example of a Redox reaction reduced (GER) NaCl + Na + Cl oxidized (LEO) since Cl takes an e- from Na ----- Cl is the oxidizing agent since Na loses an e- to Cl ----- Na is the reducing agent 12 Redox without transfer of electrons sometimes redox results in change in how electrons are shared between covalent bonds reduced CH3 + O2 oxidized CO2 + H2O energy! how did the position of electrons around C and O change? 13 Where is the energy coming from when we break a chemical bond?? reduced (GER) CH3 + O2 oxidized (LEO) CO2 + H2O energy! 14 notice the location of electrons Fig 9.3 15 Summary Solar energy converted to chemical energy by photosynthesis Consumers use potential energy contained in chemical bonds to do work. How? During catabolic (break down) reactions - electrons in chemical are relocated from a high energy state to a lower energy state - an electron loses energy when it moves from a less electronegative atom to a more electronegative atom - energy captured during this step is used to do work! 16 Cellular Respiration C6H12O6 + 6O2 high electrons energy 6CO2 + 6H2O + energy (ATP and heat) low energy - enzymes facilitate this reaction - enzymes can be regulated - energy is released in discreet steps 17 Why do we need food? Food (carbohydrates, fats, proteins) donates electrons in the form of H atom electrons are first harvested by a coenzyme called NAD+ 18 How | H - C - OH | (part of a sugar) + NAD works | C = O + NADH + H+ | dehydrogenase + NAD+ Dehydrogenases remove 2 H atoms (2 electrons and 2 protons) NAD+ accepts 2 electrons and one proton the other proton is released to surroundings 19 + NAD an electron acceptor that functions in respiration accepts two electrons and one proton to form NADH **very little energy is lost in the transfer of electrons to NAD+ Fig 9.4 20 Why do we need food? Fig 9.4 21 Fig 9.5 22 Overview Step 1. Respiration involves taking electrons from chemical bonds in food in the form of hydrogen atoms Step 2. Electron transport chain `breaks the fall' of the electron from high energy state to low energy state, gathers released energy 23 e- e- proteins hand down e- to each step, controlled energy recovery ee- free energy explosion ee- eeO2 electron falling down potential energy gradient electron handed down potential energy gradient 24 Fig 9.6 25 Overview Step 1. Glycolysis - break down glucose to pyruvate, get electrons (occurs in cytosol) Step 2. Citric acid cycle - break down pyruvate to CO2 (occurs in mitochondria) Step 3. Oxidative phosphorylation - use energy collected in NADH to phosphorylate ADP - making ATP! (occurs in mitochondria 26 Summary Respiration Relocation of electrons releases energy stored in bonds - Reduction-oxidation (redox) reactions Energy is harvested in small increments - Glycolysis - Citric acid cycle - Oxidative phosphorylation 27 Next Time Glycolysis and the Citric Acid Cycle 28 ...
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This note was uploaded on 05/06/2008 for the course BIO 311C taught by Professor Satasivian during the Spring '08 term at University of Texas.

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