Lecture 14 Chapter 15 Metabolism Metabolism ATP as the universal currency of free energy Coupled Reactions Activated carriers Regulation of metabolic processes 1 What is Metabolism The complex of physical and chemical processes occurring within a living cell or organism that are necessary for the maintenance of life Photosynthesis autotrophs Biosynthesis anabolism Oxidation of fuel molecules catabolism chemoheterotroph 2 Energy is released from glucose in a stepwise fashion 3 Oxidation of single carbon compounds 4 Two main types of Cellular Fuel 5 Oxidation Reduction reactions Overview Reduction Gain of e loss of oxygen gain of hydrogen Aox Bred Ared Box Oxidation Loss of e gain of oxygen loss of hydrogen 6 Catabolism Metabolism Anabolism Oxidation of carbon fuel HIGH Enthalpy LOW Entropy Higher free energy NADH FADH2 NADH LOW Enthalpy HIGH Entropy Higher free energy 7 The Stages of Catabolism 8 Phosphoric Anhydride Linkages Phosphoryl Groups with High Transfer Potential in Adenosine Nucleotides 9 Adenosine 5 Triphosphate ATP BASE Adenine Sugar Ribose Phosphoester bond 10 Arginine Finger ATPase activity Threonine Aspartate Hydrolysis of Phosphoric Acid Anhydrides is Highly Favorable G 30 5 kJ mol 1 Orthophosphate Pi 12 J G 45 6 kJ mol 1 pyrophosphate PPi 13 Hydrolysis of Pyrophosphate Is Also Thermodynamically Favorable pyrophosphate PPi J G 33 6 kJ mol 1 Pi H Pi H 14 The High Phosphoryl transfer Potential of ATP results from structural differences between ATP and its hydrolysis Products 1 Electrostatic Repulsion 2 Resonance Stability 3 Stabilization due to hydration 4 Increased entropy 15 ydrolysis of ATP Causes the Relief of Charge Repulsi 16 Resonance Structures of Orthophosphate Pi 17 There are fewer resonance structures available to the phosphate of ATP than to free orthophosphate 18 What is the Daily Human Requirement for ATP Resting human consume about 40 kg of ATP in 24 hours and up to 0 5 kg per minute of strenuous exercise This is equivalent to 60 kg for a 2 hr run The typical adult human body contains 50 100 g of ATP ADP Thus each ATP molecule must be recycled nearly 1300 times per day The typical ATP molecule is consumed within 1 min of its production 19 Three ways to make ATP in Eukaryotes 1 Substrate level phosphorylation Phosphate is transferred to ADP in a coupled reaction involving from a molecule with an high phosphoryl group transfer potential 2 Creatine kinase 3 Oxidative phosphorylation during Cellular respiration by ATP phosphatase 20 Molecules with High Phosphoryl Group Transfer Potential 21 Coupled Reaction For Production of ATP Substrate level Phosphorylation Reactions 1 and 2 are coupled 1 PEP H2O pyruvate Pi 2 ADP Pi 3 PEP ADP pyruvate ATP Overall G 31 5 kJ mol ATP H2O G 62 2 kJ mol G 30 5 kJ mol G overall G reaction 1 G reaction 2 If the net G value G overall is sufficiently negative forming the products eg pyruvate and ATP is an exergonic process 22 The Large Negative Free Energy Change of ATP Hydrolysis Drives many Unfavorable Reactions in the Cell Example Phosphorylation of glucose is driven by hydrolysis of ATP ATP H2O ADP Pi glucose Pi G 6 P H2O glucose ATP G 6 P ADP G reaction 1 30 5 kJ mol G reaction 2 14 kJ mol Coupled reactions G overall 16 5 kJ mol 23 Three ways to make ATP in Eukaryotes 1 Substrate level phosphorylation Phosphate is transferred to ADP in a coupled reaction involving from a molecule with an high phosphoryl group transfer potential 2 Creatine kinase 3 Oxidative phosphorylation during Cellular respiration by ATP phosphatase 24 Sources of ATP during Exercise Anaerobic 25 Important properties of high energy compounds 1 Transient forms of stored energy Phosphogen Creatine phosphate 2 Thermodynamically unstable Favorable spontaneous 1 Kinetically stable Does not hydrolyze unpredictably 26 Activated Carriers during Catabolism ADP ATP NAD NADH FAD FADH2 FMN FMNH2 27 Dehydrogenation Reaction reduced oxidized oxidized reduced 1 H 1 e 1 H 1 e H hydride 2 e 1 H or H 1 e Error on p 257 of text says hydrite H 2 e 28 Nicotinamide Adenine Dinucleotide NAD NAD Collects Electrons Released in Catabolism 29 NAD Mechanism 30 FAD Flavine Adenine Dinucleotide Riboflavin a watersoluble vitamin Vit B2 31 FMN an electron carrier component of the ETC Isoalloxazine ring D ribitol 32 Reduction of FAD FMN or FMN or FMNH2 33 FAD Mechanism 34 Activated Carriers during Anabolism ADP ATP NADP NADPH 35 Reductive Re hydration Biosynthesis 36 Nicotinamide adenine dinucleotide phosphate NADP 37 Activated Carrier of Acyl Group Coenzyme A CoA or CoASH ADP Vitamin B5 38 39 Two characteristics are common to activated carriers 1 The carriers are kinetically stable in the absence of specific catalysts 2 The metabolism of activated groups is accomplished with a small number of carriers 40 B3 B5 B7 B9 41 Regulation of Metabolic Pathways 1 Amounts of enzyme are controlled 2 Accessibility to substrates is regulated 3 Catalytic activity is regulated 4 Posttranscriptional modification of enzymes Allosteric regulation Organized into pathways 42
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