HUN1201 Exam III Study Guide Chapter 7 What are the 3 possible fates of glucose in the liver o Phosphorylated and metabolized for energy or stored as glycogen o Released into circulation for other cells to use as fuel or stored as glycogen muscle tissue o Converted to fatty acids if glucose exceeds energy needs and stored as triglycerides in adipose tissue What are the 3 Phases of glucose oxidation o 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 o What are the starting products and ending products of each phase During oxidative phosphorylation the NADH and the FADH2 enter the electron transport chain o What is produced in each phase ATP is produced Explain the TCA cycle What molecule is entering the TCA cycle and where is it coming from o Glucose first undergoes Stage 1 Glycolysis in which it is converted from glucose to yield 2 pyruvate Then in a transition reaction the two pyruvate are converted into two Acetyl CoA and the TCA Cycle begin can now begin o What molecule is recycled in the TCA cycle Oxaloacetate is derived primarily from carbohydrates and can be synthesized from amino acids It is used up in the first step of the TCA cycle and regenerated in the final step In this way Oxaloacetate could be thought of as a rate limiter o What is the fate of the carbons entering the TCA cycle as Acetyl CoA In aerobic metabolism each of the two pyruvate molecules produced from Glycolysis undergoes one rotation of the TCA cycle to yield 230 32 ATP water and CO2 What are the starting and end products of lipolysis o Start Triglycerides o End A glycerol backbone and three fatty acids What happens to the glycerol produced by lipolysis o Glycerol can be a converted to glucose or b oxidized for energy o What happens to the fatty acids produced by lipolysis Free fatty acids are oxidized for energy but cannot be converted into glucose o Explain this process what are its end products Fatty acids are activated by the addition of Coenzyme A the same enzyme used in the synthesis of acetyl CoA from pyruvate This reaction requires a small investment of ATP The fatty acid can now be shuttled across the mitochondrial membrane by carnitine What molecule is common to CHO lipid protein and alcohol metabolism The end products of fatty acid oxidation are carbon dioxide water and ATP o All can form acetyl CoA Why can fatty acids not be converted into glucose o There is no metabolic pathway to convert acetyl CoA into pyruvate Cells cannot convert acetyl CoA to glucose Explain why ketones are produced o As previously mentioned the TCA cycle functions only if there is adequate oxaloacetate a carb derivative If a person is following a very low carbohydrate diet which increases fat catabolism or has had too little functioning insulin to allow glucose to enter cells oxaloacetate production falls and the TCA cycle activity decreases As fat catabolism continues during this carb depleted state acetyl CoA continues to accumulate faster than the TCA cycle can metabolize it due to mostly to insufficient oxaloacetate and collects in the liver In order to compensate the liver diverts the acetyl CoA to another highly less efficient metabolic pathway This leads to the production of ketone bodies Which molecule is lacking in the TCA cycle and why is it lacking Why does this cause ketone production Oxaloacetate see above When does the body utilize proteins for energy o Protein is used for fuel primarily when total energy or carbohydrate intake is low What is the first step in this process and why is it necessary o In order to process amino acids for energy the nitrogen or amine group must first be removed This first step in proteolysis is called deamination What happens to the molecules produced in this first step hint there are 2 molecules produced o The end products of deamination are ammonia derived from the amine group and the remaining carbon skeleton often classified as a keto acid NOT THE SAME AS A KETONE The carbon skeleton produced can then be channeled into What are the enzymes involved in alcohol metabolism and what are their Glycolysis or the TCA pathway functions o Alcohol Dehydrogenase ADH First contact with alcohol Oxidizes alcohol into acetyldehyde o Aldehyde dehydrogenase ALDH Oxidizes acetyldehyde into acetate which is then converted to acetyl CoA o Where is alcohol oxidized 2 places Stomach Liver o What is the average rate of alcohol metabolism One drink per hour How do we store excess energy in the body o In the fed state the body converts newly absorbed glucose fatty acids and amino acids into stored glycogen and triglycerides What occurs in the different anabolic and catabolic states carbs fats pro o Anabolic body oxidizes carbs for energy and only metabolizes fat and protein for fuel if the meal does not provide sufficient carbs Glucose in excess of energy needs is converted to glycogen and stored in liver and muscles Once glycogen stores are saturates any remaining glucose is converted to fatty acids and eventually stored as triglycerides Metabolic responses to fasting starvation resting physical activity o Short term fasting Liver glycogen is broken down to balance blood glucose levels When liver stores run out most body cells including muscle cells switch to the use of fatty acids as fuel to conserve glucose for the brain and other cells that rely heavily on glucose Ketone bodies accumulate Glucose is synthesized from glycogenic amino acids in blood then from muscles These adaptions are only meant to be short term o Starvation Once fatigue sets in there is a sharp decline in voluntary physical activity core body temp drops resting metabolic rate declines Essentially body takes energy and concentrates it on the vital systems Fatty acids are now the main source of energy and the brain now uses ketone bodies as fuel o Resting To maintain homeostasis the body must regulate energy storage and breakdown as needed The primary anabolic hormone is insulin whereas glucagon epinephrine and cortisol are catabolic hormones Chapter 14 post exercise Fuel energy needs for Physical Activity different intensities during and o TABLE 14 6 IN BOOK o Aerobic metabolism in mitochondria Fatty Acids Acetyl CoA Glucogenic Amino Acids pyruvate Ketogenic Amino Acids Acetyl CoA o Anaerobic metabolism in cytoplasm TCA Cycle Electron Transport chain Heat Illnesses
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