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Exam 2 Review Bioenergetics Overview a Cells require energy Cells use sunlight electromagnetic radiation photosynthesis or chemical nutrients with high potential energy cellular respiration b These external sources of E are converted into a chemical E carrier adenosine triphosphate ATP ATP is generated from ADP and inorganic phosphate Pi Cells use the E released during hydrolysis of the high E phosphoanhydride bond in power its other processes ATP to 2 processes Aerobic oxidation Occurs in mitochondria of eukaryotic cells Sugars carbohydrates and fatty acids hydrocarbons both derived from digestion These are oxidized and the E released from there chemical bonds is converted into the of food contain E in there chemical bonds terminal 2 Photosynthesis phosphoanhydride bond of ATP Chloroplasts of plant cells and some bacteria Radiant E of light is absorbed by pigments and used to make ATP and carbohydrates Uses CO2 as a substrate and generates O2 and carbohydrates as a product Chemiosmosis A mechanism common to mitochondria bacteria and chloroplasts Proton electrochemical gradient is generated across membrane driven by E released as electrons travel through an electron transport chain The E stored in this gradient proton motive force that is used directly to power the synthesis of ATP and other E requiring processes Aerobic Oxidation Hydrocarbon fatty acids and carbohydrates sugar with energy stored in the chemical bonds are combusted and this is coupled to ATP synthesis Comprised of multiple steps that are catalyzed by specific proteins Glucose Oxidation Conversion in cytosol of 1 6 carbon glucose molecule to 2 3 carbon pyruvate molecules glycolysis Pyruvate oxidation to CO2 in the mitochondrion via a 2 carbon acetyl CoA intermediate Citric Acid Cycle Electron transport chain to generate a proton motive force ATP synthesis in the mitochondiron Oxidative phosphorylation Substrate Level Phosphorylation vs Oxidative Phosphorylation Substrate Level Phosphorylation Formation of ATP from ADP and Pi catalyzed by cytosolic enzymes in reactions that do NOT depend on a proton motive force or molecular oxygen C C chemical bond AT P chemical bond Oxidative Phosphorylation The phosphorylation of ADP to from ATP driven by the transfer of electrons to oxygen O2 Involves the generation of a proton motive force during electron transport and its subsequent use to power ATP synthesis C C chemical bond Reducing power e Proton motive Force AT P Glycolytic bond Stage I GLYCOLYSIS Pathway Occurs in cytosol Does NOT require oxygen Anaerobic glucose catabolism Biological breakdown of complex to simpler substances Converts 1 glucose into 2 pyruvate molecules The free E released in this process is used to form the high E compounds ATP and NADPH a 4 ATP molecules are generated Substrate level phosphorylation Requires initial input of 2ATP molecules that are used to make 2ADP molecules that will go on to generate 4ATP molecules Glycolysis yields net of 2 ATP molecules glucose molecule b Chemical equation for glucose 2 pyruvate c In reaction 6 The 4 e s and 2 of the H s are transferred to 2 molecules of NAD Used to produce the reduced form NADH 2H 4e 2NAD 2NADH Reducing power of NAD and FAD II is drive the Some of the energy released in the early stages of oxidation Stage I and Stage temporarily stored in the reduced coenzymes NADH and FADH2 These are energy carriers that carry high energy electrons that subsequently electron transport chain So the complete overall equation for glycolysis C6H12O6 2NAD 2ADP 2Pi 2C3H4O3 2NADH 2ATP 2H 2H2O At this point only some of the E available has been used to produce ATP the rest is chemical bonds of the pyruvate molecule and some in the high E electrons stored in the of NADH Allosteric regulation of glucose metabolism Stages I and II are both closely regulated so as to produce only the needed amount of metabolites intermediates and not excess Glycolysis is regulated by slowing down or speeding up certain steps in the pathway controlled by three allosteric glycolytic enzymes Allostery Any change in a proteins 3 or 4 structure induced by the non covalent binding of a ligand Allosteric protein Have multiple binding sites for ligands Allosteric change in activity can either be positive or negative Three steps that are rate limiting and irreversible Step 1 Hexokinase is inhibited by its product glucose 6 phosphate Step 10 Pyruvate kinase is inhibited by ATP glycolysis is slowed down when ATP concentrations are too high Step 3 Phosphofructokinase 1 Principal rate limiting enzyme of the pathway Allosterically controlled by many molecules Inhibited by ATP and citrate Activated by AMP fructose 2 6 biphosphate and Insulin Anaerobic vs Aerobic Metabolism of Glucose What happens to the pyruvate that was formed in glycolysis depends on whether or not there is oxygen present Anaerobic In absence of oxygen the products of glycolysis remain in the cytoplasm The 2NADH molecules that were produced during glycolysis are oxidized and regenerated back that is converted to ATP chemical bond into NAD And the only chemical bond energy Energy is the net gain of 2 ATP that occurred in glycolytic pathway In yeast this process Fermentation In animals Pyruvate is converted to lactic acid Aerobic Cellular Respiration In the presence of oxygen there is a transfer of chemical bond energy pyruvate transporter and reducing power NADH via electron pyruvate via shuttle to mitochondrion matrix Reactions in the mitochondria II IV generate 28 more ATP molecules Transportation of products from glycolysis into mitochondria Products of glycolysis in the cytoplasm must get to mitochondria for steps II IV Pyruvate Move through outer membrane via semi permeable porins Move through inner membrane impermeable via pyruvate uniporter protein transporter into the matrix Fatty acid CoA the stage I product of fatty acid is also transported through the membrane first via a semi permeable porin And then through a specific uniporter on the inner membrane to get into the matrix outer fatty acid CoA NADH Move through outer membrane via semi permeable porins Moves through inner membrane via electron shuttle further explained later Bypasses Stage II and go directly into stage III Stage II CITRIC ACID CYCLE Once pyruvate is transported into matrix above stage II begins Two parts overall 1 Generation of acetyl CoA 1 CO2 and 1 NADH 2 Conversion of acetyl CoA into 2 CO2 3 NADH FADH and GTP So most of the energy is converted into

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FSU PCB 3134 - Exam#2 Review

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