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How do our cells and other living organisms get energy from organic polymers (i.e. food)? Cellular Respiration (2.8/8.2) Review: • How ventilation and gas exchange different from respiration? • What are redox reactions? • What is phosphorylation? HL Only: • What is carboxylation? • What is chemiosmosis? Oxidation-Reduction (Redox) Reactions in Cellular Respiration “OIL ” • Removal of hydrogen • Addition of oxygen “RIG” • Addition of hydrogen • Removal of oxygen Why cellular respiration? • All living organisms respire to produce ATP (adenosine triphosphate) from organic molecules • ATP is used for cellular processes– energy stored in chemical bonds • In plants, cellular respiration is dependent upon the end-products produced in photosynthesis • Breathing is NOT respiration (aerobic respiration requires oxygen – i.e. purpose of ventilation and gas exchange) Definition & Chemical Equation for Cellular Respiration Definition: controlled release and conversion of chemical energy stored in carbon compounds to ATP Role of Enzymes in Respiration • Metabolic pathway controlled by enzymes ; rate controlled by end product inhibition (Amount of ATP determines rate of reaction ; if there is adequate supply of ATP, ATP will block the attachment of more substrate) • ATP binds to the allosteric site of the starting enzyme (binding site for non-substrates) Which has more mitochondria? Why? Muscle Cell Micrograph Skin Cell Micrograph What is the structure of the mitochondria? Structure of Mitochondria Ex: ATP Synthase What are the 4 stages of aerobic respiration? Where does each stage occur? • Glycolysis occurs in the cytoplasm • The Link Reaction occurs in the matrix • The Krebs Cycle occurs in the matrix • The ETC occurs along the inner membrane • Glycolysis can occur with or without oxygen (aerobic or anaerobic respiration) • Yields a small amount of ATP • Produces pyruvate, which can be further broken down to lactate OR ethanol (fermentation) Why can’t we just keep doing anaerobic respiration? • Ethanol and lactic acid products can become toxic • Production of ethanol is not reversible. If levels get too high it will kill the organism. • Lactic acid can be reversible, but requires oxygen. • Oxygen debt – lack of oxygen that needs to be repaid in order to convert lactic acid into carbon dioxide and water (this is why we continue breathing deeply and frequently after we’ve already stopped exercise) • Source: http://ibbiologyhelp.com/OptionB/oxygendebt.png 4 Stages of Glycolysis (glycol = sugar ; lysis =splitting) 1. Phosphorylation of Glucose 2. Lysis 3. Oxidation of T.P. 4. Formation of ATP Animation: http://highered.mheducation.com/sit es/0072507470/student_view0/chap ter25/animation__how_glycolysis_w orks.html 1 2 3 4 • Step 1 - Glucose is phosphorylated (two phosphate groups are added to glucose to form hexose biphosphate). These two phosphate groups are provided by two molecules of ATP. • Step 2 - Lysis of hexose biphosphate. Hexose biphosphate splits into two molecules of triose phosphate. • Step 3 - Each triose phosphate molecule is oxidized (hydrogens and electrons are removed from each molecule). NAD+ accepts the electrons and hydrogen lost by TP, and gets reduced to NADH. Energy is released from the oxidation of each molecule of TP. • Step 4 – The energy released by the oxidation of TP is used to phosphorylate two molecules of ADP. Two pyruvate molecules are formed by removing two phosphate groups from each molecule. These phosphate groups are given to ADP molecules and form ATP. Products and (Summary) of Glycolysis: • ONE glucose is converted into TWO pyruvates. • A net yield of TWO ATP molecules • TWO NAD+ are reduced to + Oxidation in Glycolysis • Two atoms of hydrogen are removed from each triose phosphate molecule. This is oxidation. • These two atoms of hydrogen are added to NAD+ to make NADH & H+. This is reduction. Link Reaction by Oxidative decarboxylation • Occurs in mitochondrial matrix • Pyruvate is converted to acetyl CoA through oxidative decarboxylation and combination with coenzyme A • Oxidation = loss of hydrogen/electrons • Decarboxylation = removal of CO2 • Acetyl CoA and NADH are used in the Krebs Cycle The Krebs Cycle • Acetyl CoA (2C) is combined with a 4C compound (oxaloacetate) to make a 6C intermediate (citrate), which is broken down in a series of reactions to reform the 4C compound Reaction Types: • Decarboxylation: CO2 is removed and excreted as waste • Oxidations: hydrogens are removed and accepted by NAD and FADH ; energy released is stored in hydrogen carriers • Substrate-level phosphorylation: ATP is produced • Link Reaction and Krebs Cycle Animation: http://highered.mheducation.com/sites/0072507470 /student_view0/chapter25/animation__how_the_kre bs_cycle_works__quiz_1_.html (Oxaloacetate) •2 molecules of CO2 are released •NADH & FADH2 are sent to the ETC (Citrate) The ETC and Oxidative Phosphorylation •Electrons are brought to the chain by NADH and FADH2, and move through protein complexes to release energy •Energy from the movement of electrons is used to pump H+ ions in to the intermembrane space to produce a concentration gradient for chemiosmosis •ATP Synthase is used to generate energy for phosphorylation of ADP The Role of Oxygen in Aerobic Respiration •Oxygen = “terminal electron acceptor” •Oxygen accepts electrons at the end of the ETC and H+ ions to form water as a byproduct of aerobic respiration IB Prompt: Explain oxidative phosphorylation in terms of chemiosmosis • Oxidative phosphorylation involves using energy from the oxidation of hydrogen carriers (NADH / FADH2) to phosphorylate ADP, and make ATP. •Energy is generated as electrons move through the electron transport chain, and is used to pump hydrogen ions (H+) from the matrix into the intermembrane space •This generates a concentration gradient which drives the hydrogen ions back into the matrix through enzymes called ATP Synthase. •ATP synthase uses energy generated by the movement of H+ ions to make ATP from ADP; this process of making ATP by the movement of H+ is called chemiosmosis.