BIOLOGY 111 1st Edition Lecture 11 Outline of Last Lecture I Equilibrium A Open vs Closed systems B Exergonic reactions and Endogonic reactions II ATP III Catalyst A Enzyme and Ribozymes B Activation Energy and Transition State IV Enzymes A Purpose B Active Site and Induced Fit C Environment factors V Inhibitors A Competitive vs Noncompetitive inhibitor B Feedback inhibitor Outline of Current Lecture I Energy Flow II Cellular Respiration III Redox Reactions IV Pathways of Cellular Respiration V Cancer Cells VI Catabolism VII Feedback Inhibition Current Lecture Energy flow Energy flows into an ecosystem as sunlight and leaves as heat These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute The chemical elements essential to life are recycled Photosynthesis generates oxygen and organic molecules used by mitochondria as fuel for cellular respiration Carbon dioxide and water are the products of photosynthesis The reactants create products and the products are used as the reactants in a continuous cycle Cellular Respiration Includes aerobic with oxygen and anaerobic without oxygen processes although it mostly refers to aerobic process It is a metabolic process i e burning fuel Fats proteins carbohydrates glucose are broken down to make carbon dioxide water and energy Glucose is most often used by cells Exergonic free energy of 686kcal per mole This means glucose products contain less energy than the reactant glucose and it occurs spontaneously Redox Reactions When in a chemical reaction there is a transfer of one or more electrons from one reactant to another Oxidation Reduction reaction Electrons are transferred to more electronegative atoms forming a more stable arrangement Oxidation loses electrons considered oxidized because increasing the positive charge by losing an electron negative charge Oxidizing Agent electron acceptor the one being reduced Reduction gains electrons considered a reduction because decreasing the positive charge by gaining an electron negative charge Reducing Agent electron donor the one being oxidized Dehydrogenations lost electrons are accompanied by hydrogen therefore what is lost is a hydrogen atom 1 electron and 1 proton Aerobic Process In the presence of oxygen The oxidation of glucose provides abundant energy making about 36 molecules of ATP for every molecule of glucose Glucose is ALWAYS oxidized Oxidation of glucose occurs in several small steps this allows the cell to capture energy for further use which is stored by NAD NAD for every conversion of NAD to NADH 2 hydrogens are removed from substrate one H is binding the other H is released NADH passes the electrons to the electron transport chain Three Metabolic pathways of Cellular Respiration the harvesting of energy from glucose by cellular respiration is a cumulative function of the following pathways 1 Glycolysis sugar splitting Occurs in the cytosol Begins the degradation process by breaking glucose into two molecules of pyruvate With Oxygen Pyruvate enters the mitochondria and is oxidized into acetyl CoA and enters the Krebs cycle per molecule of pyruvate products include 1 CO 2 1 NADH and 1 acetyl CoA which consist of 2 carbons from pyruvate attached to coenzyme A Without Oxygen Pyruvate is reduced and oxidizes NADH back to NAD which is a process called Fermentation Respiration yields more ATP 16 times as much ATP than Fermentation Substrate level phosphorylation formation of a small amount of ATP 2 Citric acid cycle Kreb s cycle This is where the acetyl CoA enters Steps per cycle include release of 2 molecules of CO2 per 1 cycle reduce 3 NAD to 3 NADH per 1 cycle reduce 1 FAD to FADH2 per 1 cycle produce 1 ATP per 1 cycle the cycle turns twice for each original glucose molecule Coenzyme A the remaining 2 carbons not used for CO2 attach to this carrier molecule that is a sulfur containing compound derived from vitamin B Carbon dioxide produced by respiration represents fragments of oxidized organic molecules Substrate level phosphorylation Oxidative phosphorylation most of the ATP synthesis occurs at this stage After glycolysis pyruvate oxidation and the kreb s cycle glucose has been oxidized to o 6 Carbon Dioxide molecules o 4 ATP o 10 NADH o 2 FADH2 The 10 NADH and 2 FADH2 are passed on to the electron transport chain The ETC electron transport chain accepts electrons from the breakdown products of the first two stages through the NADH and passes these electrons from one molecule to another At the end of the chain the electrons are combined with molecular oxygen and hydrogen ions forming water The energy released at each step is stored in a form the mitochondria can make use of i e ATP from ADP Chemiosmosis the energy stored in the form of hydrogen ion gradient across a membrane is used to drive cellular work i e ATP synthesis For each molecule of glucose degraded into Carbon Dioxide and water by respiration the cell makes about 32 molecules of ATP Cancer cells favor glycolysis Warburg effect cancer cells preferentially use glycolysis while decreasing oxidative phosphorylation this isn t the cause it is the result Glycolytic enzymes are expressed in 80 of all types of cancer Caused by genetic and environmental factors i e mutations low oxygen Catabolism Carbohydrates fats and proteins can all be used as fuel for cellular respiration Monomers of these molecules enter glycolysis or citric acid cycle at various points Proteins enter as amino acids and before they can enter glycolysis or citric acid cycle the amino group must be removed which is called deamination Fats are digested as glycerol and fatty acids Glycerol is converted to glyceraldehyde 3 phosphate and enters glycolysis Fatty acids are broken down by beta oxidation into two carbon fragments before they can enter Kreb s cycle as acetyl CoA Feedback Inhibition Regulates Cellular Respiration by allosteric enzymes that set the pace of glycolysis and citric acid cycle If your body has enough ATP then the process stops and excess food molecules are stored as glycogen or fat