- BIO115 Cellular Respiration Dr Jessica Pamment Overview Overview • • • i ii iii • Energy flow producers and consumers Aerobic

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Unformatted text preview: BIO115 Cellular Respiration Dr. Jessica Pamment Overview Overview • • • i. ii. iii. • Energy flow; producers and consumers Aerobic respiration: cellular respiration 3 stages: Glycolysis Citric Acid Cycle Electron transport chain Anaerobic respiration: fermentation Energy Flow and Chemical Cycling in Ecosystems Sunlight energy enters ecosystem 6 12 6 2 Photosynthesis Cellular respiration ATP drives cellular work Heat energy exits ecosystem Producer Producer and consumer Cellular Respiration Cellular Respiration • The aerobic harvesting of chemical energy from organic fuel molecules • Oxygen in the air we breathe in is required for cellular respiration • Carbon dioxide is a by product found in the air we exhale How breathing is How breathing is related to cellular respiration Cellular Respiration Cellular Up to 38 ATPs generated per glucose molecule You need 10 million ATP molecules per second to power one active muscle cell REDOX Reactions Redox Reactions Redox Reactions • Reduction­oxidation reactions • Reactions that transfer electrons between reactants • A substrate that gains electrons is said to have been reduced • A substrate that has lost electrons is said to have been oxidized Redox Reaction Redox becomes oxidized (loses electron) becomes reduced (gains electron) Electron Transfer and Energy Electron Transfer and Energy Release • Electrons release energy when moved from one atom to another • Release of energy used for ATP synthesis • Electrons are transferred to oxygen in a stepwise manner A rapid A rapid electron ‘fall’ The role of The role of oxygen in harvesting food energy NAD+ and Electron Transport NAD+ and Electron Transport Chain • Transport chain consists of mainly proteins built into the inner membrane of mitochondria • NADH releases electrons that are passed by a series of redox reactions down the chain until they reach oxygen • Energy is released in a stepwise fashion 3 Stages of Respiration 3 Stages of Respiration • Respiration is a metabolic pathway • 3 main metabolic stages: 1.Glycolysis 2.Citric acid cycle 3.Electron transport The three stages of cellular respiration The three stages of cellular respiration Glycolysis Glycolysis • • • • ‘Splitting of sugar’ Takes place in all living things Anaerobic process Takes place in cytosol Glycolysis Glycolysis • Results are: 1.2 ATP molecules 2.2 NADPH molecules 3.2 pyruvic acid molecules • Releases less than 25% of chemical energy stored in glucose Glycolysis 2 ATP 2 NADH 6C glucose 2 x 3C pyruvic acid The link between Glycolysis and the The link between Glycolysis and the Citric Acid Cycle The Citric Acid Cycle The Citric Acid Cycle • A.K.A Kreb’s Cycle, finishes the breakdown of glucose • Takes place in the mitochondrial matrix • Is the major source of electrons that are transported to the electron transport chain form of electrons • Most energy is transferred to NAD+ and FAD+ in The Citric Acid Cycle The Citric Acid Cycle • Citric acid cycle turns twice for each glucose molecule because two acetic molecules derived from one glucose molecule • 3 CO2 per cycle (6 CO2 per glucose molecule) • 1 ATP per cycle (2 ATPS per glucose molecule) • 3 NADH per cycle (6 NADH per glucose molecule) • 1 FADH2 per cycle (2 FADH2 per glucose molecule) The role of The role of oxygen in harvesting food energy Electron Transport Chain Electron Electron Transport Chain Electron Transport Chain • Takes place in the inner mitochondrial membrane in eukaryotes complexes • Components of chain are multiprotein • Complexes arranged in order from less to more electronegative • Electrons passed down by redox reactions Electron Transport Chain • Energy released as electrons transferred between complexes • Energy released used to make ATP • 1000s of chains found in any one mitochondria • 34 ATP molecules produced in the ETC Energy Energy from Food Summary of ATP yield during cellular respiration Summary of ATP yield during cellular respiration In the absence of oxygen…. In the absence of oxygen…. • Cells can oxidize organic fuel and generate ATP without the use of oxygen by fermentation Fermentation Fermentation • Harvests chemical energy without the use of ETC • It’s an expansion of glycolysis that allows continuous generation of ATP • Results in recycling of electron carriers without use of ETC Lactic Acid Fermentation 2 ATP Recycling electron carriers Glucose 2Pyruvic acid 2Lactic Acid Alcoholic Fermentation 2 ATP 2CO Recycling electron carriers Glucose 2Pyruvic acid 2Ethyl alcohol Yeast Yeast Respiration vs. Fermentation Respiration vs. Fermentation Respiration ATP synthesis Oxidation of organic molecs Final electron acceptor ATP yield Aerobic Glycolysis Oxygen 38 ATPs Fermentation Anaerobic Glycolysis Pyruvate 2 ATPs Fermentation vs. Respiration Fermentation vs. Respiration • Both metabolic reactions produce ATP • Fermentation is the partial degradation of sugar without the use of oxygen • Aerobic Respiration is the breakdown of sugars with the use of oxygen Evolution Connection Evolution Connection • Glycolysis is the most widespread metabolic pathway • Glycolysis takes place in the cytosol • Glycolysis occurs under both aerobic and anaerobic conditions • Suggests it evolved early 0 A Time line of oxygen and life on Earth O present in Earth’s atmosphere Billions of years ago 2.1 2.2 2.7 First eukaryotic organisms Atmospheric oxygen reaches 10% of modern levels Atmospheric oxygen first appears 2 3.5 Oldest prokaryotic fossils Origin of Earth 4.5 Summary Energy Flow Summary Energy Flow Ultimately all energy comes from the sun Summary of Respiration Summary of Respiration • Main role is to harvest energy from glucose for ATP synthesis chain ATP ATP • Energy flows: glucose NADH electron transport • 40% of potential energy in glucose transferred to • 3 stages: glycolysis, Citric Acid Cycle, electron transport chain Summary Summary • Glycolysis is the first step in harnessing energy from organic compounds • If oxygen is present, pyruvate enters the Citric Acid Cycle and ETC pathways • If oxygen is absent, pyruvate can enter fermentation Summary Summary • Most energy is made by the electron transport chain • Cell uses energy released from organic compounds to power anabolic reactions essential to life ...
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This note was uploaded on 04/26/2011 for the course BIO 115 taught by Professor Pamment during the Winter '11 term at DePaul.

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