KIN 292 1st Edition Lecture 6 These are the notes from Professor Starnes lecture of Clinical Human Physiology These come from the slideshows provided by the professor and include extra notes and explanations Highlighted or bolded information are things that I believe to be information that is important to look over multiple times The notes in red are my personal additions and quotes of Professor Starnes from the class lecture Outline of Last Lecture I Metabolic Reactions and Energy II Reaction Rates Outline of Current Lecture I II III 3 4 ATP The Medium of Energy Exchange 3 5 Glucose Oxidation The Central Reaction of Energy Metabolism 3 6 Stages of Glucose Oxidation Glycolysis Current Lecture ATP ATP for biological systems is stored within the phosphate groups Note negative charges Your instructor will demonstrate energy conversion o Has its energy because the negative charges repel because they are the same Enzyme cuts rope phosphates fly apart and propel mechanical work ATP Synthesis Energy from exergonic reactions is used to synthesize adenosine triphosphate ATP o ATP synthesis means how our body makes ATP o ADP Pi energy ATP H2O Just replacing one bond to reattach Pi don t have to synthesize entire molecule o E 7 kcal mole how much energy is in the phosphate bond Your book Based on conditions different from those in cells Actual value varies depending on relative concentrations of reactants ADP Pi and product ATP o 2 types of ATP synthesis reactions Substrate level phosphorylation Does not involve O2 X P ADP X ATP Ex Creatine kinase Oxidative phosphorylation requires electron transport chain O2 ADP Pi ATP 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 ATP Homeostasis Several metabolic pathways coordinate with one another to maintain ATP concentration constant at all times and under all conditions Variation in speed capacity and location of ATP synthesis o Some pathways are in the cytosol some are in the mitochondria o Most pathways in the cytosol make synthesis happen faster Creatine kinase reaction fastest smallest capacity Location Cytosol Very important in muscle metabolism Minor pathway in most organs Glycolysis next fastest limited capacity Cytosol Aerobic glucose oxidation pretty fast decent capacity Mitochondria Fatty acid oxidation considerably slower than above unlimited capacity Mitochondria Protein oxidation very very slow big capacity but lethal if overused Mitochondria mostly cytosol Changing concentration difference between reactants and products affects energy change E of a reaction Remember mechanical box o The greater the difference between the reactant and the product the more energy that will be produced ATP ADP Pi E Endergonic synthesis reaction ATP ADP Pi E Exergonic hydrolysis reaction for cell work 5 0 02 2 2 mM at rest E approx 10 1 kcal 4 8 0 22 2 4 mM exercise E approx 8 6 kcal Decrease in ATP and increase in ADP Pi results in increase in entropy decreased order and less energy in ATP bond Note If ATP decreases by 0 2 mM then ADP will increase by the same amount 4 in ATP results in 1 100 in ADP ADP is an important regulator of enzyme activity in metabolic pathways Low initial concentration of ADP and its huge relative increase make it one of the most important stimulators of ATP production ATP itself is much less important in regulating its own production ADP would be in the enzyme regulating zone of figure below left side and ATP would be too high on right side and not change much Bottom line the breakdown products of ATP ADP Pi are very strong regulators of metabolism and change dramatically in order to keep ATP constant at all times Creatine kinase reaction remember this takes place in the cytosol the fastest ATP producing pathway in the body It s reversible and it s a near equilibrium enzyme Obeys Law of Mass Action Tertiary structure of Creatine kinase with Creatine phosphate smaller molecule on left and ADP Law of Mass Action Increased reactant concentration relative to product pushes a reaction forward Increased product concentration relative to reactant pushes a reaction in reverse Equilibrium does not necessarily mean that you have equal amount on both the reactant and product sides aA bB cC dD a d number of molecules These reactions have an Equilibrium constant For CK K ATP Cr 100 ADP CrP Creatine Kinase Reversibility ADP Pi ATP CrP Cr Pi Pi is either connected to Cr or ADP CK ADP CrP ATP Cr ATP is used to make creatine phosphate The problem in ATP being used to create creatine is that it increases the amount of ATP in the body It can only work if other metabolic pathways have been made to synthesis the extra ATP CrP and ATP have same E at equilibrium CrP is used to phosphorylate ADP synthesize ATP when product reactant ratio is 100 ATP used to phosphorylate Cr synthesize CrP when product reactant ratio is 100 ATP homeostasis and CK If ATP used to make CrP another ATP producing pathway must replace ATP immediately because ATP cannot be allowed to drop Muscle contraction is slowed and other things are also adversely affected if ATP drops Most likely will be an aerobic pathway that replenishes ATP Figure 3 24 Metabolic pathways involved in protein glycogen glucose and fat metabolism Our author considers glucose oxidation to be the central reaction in energy metabolism because it is used in all parts of the body and other nutrients share some of the ATP producing pathways Figure 3 13 The coupling of reactions in energy transfer General scheme Glucose oxidation The central reaction of energy metabolism many ATPs heat 686 kcal mole Glucose oxidation occurs in 4 stages o Glycolysis cytosol o Krebs cycle mitochondria o Electron transport chain mitochondria o Oxidative phosphorylation mitochondria Energy Change in Glucose Oxidation o Energy released during glucose oxidation 686 kcal o Energy in 38 ATP 38 moles 7 kcal mole 266 kcal Energy of glucose temporarily conserved in ATP until it performs biological work All of this is ultimately transferred to heat which is required by 2nd Law and it also contributes to body warmth E for synthesizing ATP 422 kcal 686 266 Efficiency of ATP synthesis 266 kcal 686 kcal 38 8 Note calculations use maximum amount of ATP th synthesis of 7kcal mole Act 1 Glycolysis Key players enzymes and carriers o Hexokinase o Phosphofructokinase PFK o Glyceraldehyde 3 phosphate dehydrogenase G3PD o Lactate dehydrogenase LDH