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Transcript
Metabolism Metabolism Total of all chemical reactions that occur in the body ¾ 1. Anabolic reactions 9 Synthesis of molecules 2. Catabolic reactions 9 Breakdown of molecules Bioenergetics ¾ • Converting foodstuffs (fats, proteins, carbohydrates) into “harnessed” energy 9 ATP Food Food O2 Uncontrolled oxidation of food outside the body (burning) O2 Controlled oxidation of food inside the body ATP Explosive release of energy as heat Energy harnessed as ATP Energy released as heat ATP ATP Partly used to maintain body temperature Excess heat eliminated to the environment Figure 2.14 Page 41 1 Metabolism rates are determined by… Enzymes • Function as Biological Catalysts • Enzymes speed up chemical reactions without altering the energy release of that reaction • Determine which energy pathways are best for the particular cellular activity 9Food breakdown 9Jogging 9Sprinting Enzymes make it easier for reactions to occur! Where do we get our energy? Carbs, Proteins, Fats What is the form of energy we use in our bodies? ATP What do we do with the energy we don’t use? Expend it as heat 2 ATP & Energy Systems Energy currency of the body Adenosine triphosphate (ATP) • Consists of adenine, ribose, and three linked phosphates ¾ Formation ADP + Pi → ATP • Addition of Pi; Phosphorylation ¾ Breakdown ATP ATPase ADP + Pi + Energy • ATP splitting; Hydrolysis ATP Regeneration 3-ways: 1. Interaction of ADP and PC 9 ADP = adenosine diphosphate 9 PC = creatine phosphate or phosphocreatine (CrP) 2. Anaerobic respiration in cell cytoplasm 9 Not using O2 3. Aerobic respiration in mitochondria 9 Using O2 3 Anaerobic Energy Systems 1. Phosphagen systems 2. Glycolysis Anaerobic Energy Systems 1) Phosphagen System (in cytosol): ¾ Immediate energy sources Creatine Kinase CrP + ADP + H+ Creatine + ATP Adenylate Kinase ADP ¾ + ADP ATP + AMP Concentrations will drive reaction • ~ 10 seconds worth of energy ¾ AMP build-up stimulates gylcolysis Anaerobic Energy Systems (cont.) 2) Glycolysis (in cytosol): ¾ Prepares glucose to enter next stage of metabolism • Glucose to Pyruvate ¾ 10 or 11 step process (for 1 glucose molecule) • Begins with glucose (11) or glycogen (10) 9Occurs in Cytoplasm 9From liver, muscle or blood 9 Facilitated diffusion across muscle membrane 4 HK GLYCOGEN PFK 2 ATP Formed 2 Pyruvic Acid Molecules What to know about Glycolysis… Anaerobic energy system (in cytosol) 1. • No O2 10 (glycogen) or 11 (glucose) steps: 2. • Rate of glycolysis may increase or decrease depending on: 9 Amount of available ATP 9 Amount of available glycogen or glucose 9 HK and PFK End result = 2 ATP, 2 Pyruvic Acid 3. • Pyruvic acid either enters mitochondria or turned into lactic acid 5 Aerobic Energy Systems 1. Citric acid cycle 2. Electron transport chain Aerobic Energy System Phosphagen Systems Glycolysis Glycolysis to the Mitochondria ¾ Pyruvate can either: • Form lactic acid • Selectively transported into the mitochondria 2 major events: 1) H+ picked up by NAD 2) Formation of Acetyl CoA 6 Acetyl CoA enters the Citric Acid Cycle… Citric Acid Cycle (Krebs or TCA) produces… ¾ 8 step process after pyruvate turned into Acetyl CoA ¾ 2 CO2 ¾ 3 H+ picked up by NAD • 1 H+ picked up by FAD ¾ 1 ATP produced and used immediately in cell ¾ No O2 used, but requires presences of O2 to operate Electron Transport Chain ¾ A.K.A. ~ Oxidative phosphorylation ¾ Citric acid cycle prepares H+ carriers for ETC ¾ NADH and FADH enter ETC • Major source of energy! • Electrons held by NAD and FAD are “high energy” 9Transferred through a series of steps from one electron carrier to another 7 Electron carriers in mitochondria: • Electrons (from NAD & FAD) fall to successively lower energy levels with each step • Throughout process electrons release energy 9Used to create ATP • End by binding with O2 and forming water • Entire process creates 32 ATP molecules In Summary… Anaerobic conditions } No O2 available Glycolysis Pyruvic acid Glucose Mitochondrial outer and inner membranes Lactic acid 2 ATP Aerobic conditions Glycolysis Glucose O2 available Pyruvic acid 34 ATP + CO2 + H2O Citric acid Electron transport cycle chain 2 ATP Cytosol Mitochondrion Figure 2.15 Page 41 Cellular Respiration ¾ Energy transfer • Food to ATP • Aerobic or Anaerobic ¾ Major nutrients serve as fuel substrates • Carbohydrates 9Glucose • Fats (Triglycerides) 9Free fatty acids • Proteins 9Amino acids 8 Fat & Protein Breakdown Questions? 9