Chapter 7 Key Terms Metabolism The sum of all the chemical and physical changes that occur in body tissues 248 Anabolism The process of making new molecules from smaller ones 248 Catabolism The breakdown or degradation of larger molecules to smaller molecules 249 Adenosine Triphosphate ATP A high energy compound made up of the purine adenine the simple sugar ribose and three phosphate units it is used by cells as a source of metabolic energy 249 What are the 3 possible fates of glucose in the liver Glucose is absorbed into the bloodstream and travel to the liver where all non glucose molecules are converted to glucose Glucose is transported into the bloodstream to cells where it is either used for energy stored in the liver or muscle as glycogen or converted to fat and stored in adipose tissues 147 What are the 3 Phases of glucose oxidation Glucose oxidation occurs in three well defined stages glycolysis the TCA cycle and oxidative phosphorylation via the electron transport chain The end products of glucose oxidation are carbon dioxide water and ATP 276 Glycolysis During glycolysis six carbon glucose is converted into two molecules of three carbon pyruvate If glycolysis is anaerobic this pyruvate is converted to lactic acid If glycolysis is aerobic this pyruvate is converted to acetyl CoA and enters the TCA cycle 254 TCA Cycle During the TCA cycle acetyl CoA coming from either carbohydrate fat or protein metabolism results in the production of GTP or ATP NADH of FADH2 These two final compounds go through oxidative phosphorylation as part of the electron transport chain to produce energy 257 Oxidative Phosphorylation During oxidative phosphorylation the NADH and the FADH2 enter the electron transport chain where through a series of reactions ATP is produced Once formed the ATP can exit the mitochondria for use by all components of the cell 259 Explain the TCA cycle What molecule is entering the TCA cycle and where is it coming from What molecule is recycled in the TCA cycle What is the fate of the carbons entering the TCA cycle as Acetyl CoA TCA Cycle The tricarboxylic acid TCA cycle is a repetitive series of eight metabolic reactions located in cell mitochondria that metabolizes acetyl CoA for the production of carbon dioxide high energy GTP and reduced coenzymes NADH and FADH2 257 Acetyl CoA or Acetyl Coenzyme A Coenzyme A is derived from the B Vitamin panthothenic acid it readily reacts with two carbon acetate to form the metabolic intermediate acetyl CoA 256 The process of glycolysis starts with glucose and ends with pyruvate The linking between pyruvate to acetyl CoA also has distinct start and end points The TCA cycle is a continuous circle of 8 metabolic reactions 258 The first step of the TCA cycle begins with the entry of acetyl CoA into the cycle Pyruvate crosses from the cytosol into the mitochondria where it is converted into acetyl CoA The two carbon acetyl CoA reacts with four carbon oxaloacetate to form six carbon citrate and the metabolic cycle begins The acetyl Coa within the TCA cycle does not regenerate and the two carbons that form acetyl CoA end up within two molecules of carbon dioxide The four carbon oxaloacetate is used up in the first step of the TCA cycle and is regenerated in the final step 258 For every molecule of glucose that goes through glycolyis two pyruvate molecules are generated leading to two molecules of acetyl CoA Thus the TCA cycle mut complete two rotations for each molecule of glucose 258 From glycolyis through the TCA cycle one molecule of glucose produces the following 258 Six molecules of carbon dioxide Two ATP Two GTP Ten reduced coenzymes including the NADH from the linking step What are the starting and end products of lipolysis What happens to the glycerol produced by lipolysis 2 fates What happens to the fatty acids produced by lipolysis name the process Explain this process what are it s end products Lipolysis The enzyme driven catabolism of triglycerides into free fatty acids and glycerol 259 Triglycerides are broken down into glycerol and free fatty acids Glycerol can be converted to glucose via pyruvate or oxidized for energy Free fatty acids are oxidized to produce acetyl CoA and coenzymes which can enter the TCA cycle and electron transport chain The end products of fatty acid oxidation are carbon dioxide water and ATP Fatty acids cannot be converted into glucose With carbohydrate inadequacy fat catabolism increases and the excess acetyl CoA is diverted to ketone formation 260 Fatty Acid Oxidation or B Oxidation A serious of metabolic reactions that oxidizes free fatty acids leading to the end product of water carbon dioxide and ATP 260 Fatty acid oxidation requires an investment of energy from ATP The activated fatty acids are then shuttled across the mitochondrial membrane by a compound known as carnitine 260 Carnitine A small organic compound that transports free fatty acids from the cytosol into the mitochondria for oxidation 260 Why can fatty acids not be converted into glucose There is no metabolic pathway to convert acetyl CoA into pyruvate for glucose synthesis Because cells cannot convert acetyl CoA into glucose it is impossible for fatty acids to feed into glucose production Again there is no metabolic pathway that allows for the conversion of fatty acids to glucose 261 Explain why ketones are produced Which molecule is lacking in the TCA cycle and why is it lacking Why does this cause ketone production Acetyl CoA that enter the TCA cycle can come from glucose or fatty acid catabolism But the TCA cycle functions only when there is adequate oxaloacetate Thus if a person is following a very low carbohydrate diet which increases fat catabolism or has too little functioning insulin to allow glucose to enter cells oxaloacetate production falls and TCA cycle activity decreases As fat catabolism continues during this carbohydrate depleted state acetyl CoA builds up exceeding the ability of the TCA cycle to metabolize it and beings to accumulate in the liver cells As the acetyl CoA builds up liver cells divert it into an alternative metabolic pathway leading to the synthesis of ketone bodies When does the body utilize proteins for energy What is the first step in this process and why is it necessary What happens to the molecules produced in this first step hint there are 2 molecules produced Proteolysis The breakdown of dietary proteins into single amino acids or small peptides that are absorbed by the body 263 Proteins
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