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Biology Midterm 2 Notes - Energy.pdf

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BIOL 130
Heidi Engelhardt

Energy▯ ▯ General▯ • cells require a constant supply of energy to generate and maintain biological order that keeps them alive▯ • they get this from chemical bond energy in food molecules, aka fuel for cells▯ • plants get sugars from CO 2through photosynthesis, where animals gain it from eating other organisms ▯ cells that form the organism harvest useful energy from chemical bond energy locked • in sugars, which are oxidized into CO 2 and H 2O ▯ • this energy is stored as harvest energy (release large amounts of energy when hydrolyzed in activated carrier molecules such as ATP and NADPH)▯ ▯ The Breakdown and Utilization of Sugars and Fats▯ • living cells use enzymes to carry out the oxidation of sugars in a tightly controlled series of rxns▯ • animal cells make ATP in two ways▯ 1. Enzyme catalyzed rxns are directly coupled to the energetically unfavourable rxn ADP + Pi -> ATP▯ Most ATP synthesis occur in the mitochondria which involves activated carrier molecules which will in return drive ATP production▯ • Food molecules are broken down in three stages▯ 1. Digestion: the enzymatic break down of food molecules, which is on the outside of cells in a specialized organelle within cells called Lysosomes. Digestive enzymes reduce large polymeric units into monomeric subunits (proteins into amino acids, polysaccharides into sugars, fats into fatty acids and glycerol)▯ 2. Glycolysis: chain of reactions, where each molecule of glucose is converted into two smaller molecules of pyruvate. Two types of activated carrier molecules are produced: ATP and NADPH. Pyruvate transported from cytosol into mitochondrion’s large, matrix. Giant enzyme complex converts each pyruvate molecule into CO 2and Acetyl CoA (another carrier enzyme). ▯ 3. TCA cycle and Oxidative Phosphorylation (in Mitochondria): the acetyl group in acetyl CoA is ripped apart and transferred to a molecule called oxaloacetate to form citrate which then leads to the citric acid cycle. CO 2 is oxidized and large amounts of NADH is generated. This is then transported to along a series of enzymes within the mitochondrial inner membrane called the electron transport chain. This process includes the release of energy which leads into producing ATP and consuming molecular Oxygen. Most of the cells ATP is harnessed at this step. ▯ **Nearly half of energy that could be derived from oxidation of glucose or fatty acids to H2O and CO2 is captured and used to drive the energetically unfavourable reaction ADP + Pi -> ATP **▯ ▯ Glycolysis is a Central ATP-Producing Pathway▯ • - glycolysis produces ATP without the involvement of Oxygen▯ - occurs in the cytosol of most cells and is the only anaerobic phase of cellular respiration▯ - during glycolysis, glucose molecule (6 Carbon atoms) is cleaved into two molecules of pyruvate (which contains 3 Carbon atoms)▯ ▯ After Glycolysis the pyruvate produced must either undergo the rest of cellular respiration or fermentation. Fermentation allows ATP to be produced in the absence of Oxygen. ▯ ▯ ▯ 1. Alcoholic Fermentation: occurs in yeast and in plant cells if oxygen isn't ▯ ▯ ▯ available ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ 2.cells as well (muscle cells). Lactic acid produced can be converted back ▯ ▯ ▯ into pyruvate when oxygen is available▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ BPG= Bisphosphoglyceride Glycolysis is a process that involves 10 separate rxns each producing a different intermediate sugar and each catalyzed by a different enzyme▯ ▯ Glucose▯ ATP 1. phosphorylation by ATP ▯ pr▯ ▯ ▯ ▯ ▯ ▯ctivated molecule ADP Glucose 6 Phosphate▯ ▯ ▯ 2. Rearranged to unstable isomer Fructose 6 Phosphate▯ ATP ▯ ▯ ADP ▯ Fructose 1,6 Diphosphate ▯ 3. 2nd Phosphorylation ▯ ▯ 4. Mol▯cule sp▯its int▯ 2 DHAP▯▯ ▯ ▯ ▯ G3P▯ G3P from DHAP ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ 2G3P▯ 2NAD+ ▯ 5. DHAP rearranged to form 2G3P 2NADH 6. Oxidation of G3P produces NADH (phosphorylation of both G3P) 2P ▯ ▯ ▯ ▯ ▯ 2BPG▯ 2ADP ▯ ▯ 2ATP ▯ ▯ ▯ ▯ ▯ ▯ 2 3PG▯ 7. Substrate level phosphorylation, BPG gives ▯ up phosphate to form ATP 8. Removal of water gives PEP high energy bond H2O ▯ ▯ ▯ ▯ ▯ 2PEP▯ 2ADP ▯ ▯ 2ATP ▯ ▯ ▯ ▯ ▯ ▯ 2 Pyruvate▯ 9. 2nd Substrate level phosphorylation ▯ Glycolysis Overview:▯ Input - glucose▯ Output - 2 Pyruvate▯ ▯ 2ATP▯ ▯ O 2 H ▯ 2 ▯ 2 Phosphate Groups▯ ▯ 4 ATP▯ ▯ 2 NAD+▯ ▯ 2 NADH (~3 ATP)▯ ▯ 4 ADP▯ ▯ 2 ADP▯ ▯ ▯ **NET GAIN OF 5 ATP**▯ ▯ Glycolysis continued: ▯ • no molecular oxygen is involved in glycolysis▯ • oxidation occurs▯ • electrons are removed from some of the carbons derived from glucose by NAD+ • the synthesis of ATP in glycolysis is known as Substrate-level phosphorylation because it occurs by the transfer of a phosphate group directly from a substrate molecule (sugar intermediate) to ADP, remainder energy is stored in electrons ▯ within NADH▯ Electron Carriers▯ • NAD+ : nicotinamide adenine dinucleotide (vitamin B3)▯ • FAD: flavin adenine dinucleotide (vitamin B2)▯ ▯ • NADP+: nicotinamide adenine dinucleotide phosphate▯ NAD(P)H▯ ▯ ▯ ▯ ▯ ▯ NAD+ + H+ +2e- NADH ▯ ▯ ▯ ▯ ▯ ▯ ▯ Three ways to make ATP▯ 1. Substrate Level Phosphorylation▯ •generates a a f▯w ATP during glycolysis▯ ▯ ▯ ▯ 2. Ox•electrons harvest are used to pump H+ ions across a membrane (proton pump)▯ •protons can back up and run ATP synthase ▯ ▯ ▯ ▯ ▯ 3. Photophosphorylation▯ • occurs in chloroplasts▯ • cyclic and non cyclic phosphorylation ▯ ▯ Reduction-Oxidation (redox) reactions▯ • energy in cells, they are mobile, LEO or GER is also potential▯ ▯ ▯ Reduction and Oxidation of the Coenzyme NAD+▯ • when high energy molecules bind to enyzme, it gives up H+ (becomes oxidized, less energy)▯ • NAD+ accepts H+ and becomes reduced (more energy)▯ ▯ • the reduced energy carriers carry electrons to electron transport chain▯ Transition Reaction/ Pyruvate Oxidation:▯ • occurs in mitochondrial matrix▯ • if oxygen is only available▯ • connects glycolysis to krebs cycle▯ • CO2 is lost▯oxidized and one molecule of ▯ ▯ What is coenzyme A?▯ • an organophosphate▯henic acid, nucleotide derivative▯ • a thiol▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ ▯ Krebs Cycle = TCA (tricarboxylic acid) cycle = Citric Acid Cycle▯ ▯ Acetyl CoA (2C) Citrate (6C) Oxaloacetate (4C) NAD Isocitrate (6C) NAD+ Malate (4C) NAD+ CO2 (into atmosphere) NADH H2O Alpha-Ketoglutarate (5C) CO2 (into atmosphere) Fumerate (4C)
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