HUN 3224 Intermediate Metabolism of Nutrients I Exam II Study Guide 6. TCA Cycle (Krebs Cycle; Citric Acid Cycle) a. Know various names for this cycle. b. Recognize and be able to give examples of this cycle's role as a common metabolic pathway (e.g. where can its intermediaries originate? What can they be diverted from the cycle and used for?) c. Know reactions, enzymes, energetics, etc. d. Identify example of substrate level phosphorylation. e. Describe the role of OAA in regulating cycle activity. f. Discuss the role of NADH and ATP in controlling citric acid cycle activities. 7. Electron transport chain (ETC) a. State the purpose and cellular location and list the components of the ETC. b. Discuss how ATP is synthesized via oxidative phosphorylation. c. State why the maximum theoretical yield of ATP?s for electrons introduced into the ETC via NADH + H+ is 3, whereas for electrons introduced via FADH2 is 2. 8. Fructose and galactose metabolism a. Why are fructose and galactose metabolized primarily in the liver? b. Discuss how ingestion of large amounts of fructose may have detrimental metabolic consequences. c. Understand how fructose and galactose enter the metabolic pathways. d. Which enzyme is missing in individuals with galactosemia? C. Tissue Variations 1. Liver a. Discuss the role of the liver in glucose homeostasis. b. Discuss hormonal regulation of glucose homeostasis. 2. Muscle a. Understand that muscles are 'self-serving' in terms of CHO metabolism because of a lack of glucose-6-phosphatase. b. Note roles of insulin and GLUT 4 in glucose uptake by muscle. c. Differentiate between muscle and liver CHO pathways (major points) and their significance. d. Explain the importance of glycogen for muscles. 3. Brain a. Know that the brain is most dependent on CHO metabolism. b. Note that it is necessary for CHO metabolism in the brain to operate aerobically to meet the high energy demands of this tissue. 4. Erythrocyte (RBC) a. Explain why RBC's only operate anaerobically and how this makes them totally dependent on glucose. b. Discuss the pathways which utilize glucose; which are more prevalent and why they are necessary. 5. Know that the kidney is a major contributor to gluconeogenesis in an adapted fast. 6. Explain the utilization of glucose by adipose tissue. IV. Lipids A. Transport and uptake of lipids 1. List the different types of lipoproteins and for each give: a. Nomenclature (based on centrifugation) b. Function(s) c. Site of synthesis d. Composition - identify major lipid fraction; know relatively how much protein in comparison to lipid (e.g. HDL's have the most protein and the least lipid). 2. State the action of lipoprotein lipase (or "clearing factor"). Define: LCAT 3. Define: chylomicron remnant. 4. Describe the process whereby chylomicrons are taken up by the liver. 5. List the purposes of the apoprotein portion of the lipoproteins. 6. LDL receptor a. Describe the role of the LDL receptor in the uptake of LDL's by cells like the hepatocyte (liver cell). b. What happens to the LDL once it's inside the cell and dissociated from its receptor? c. Note that the free cholesterol released from the LDL serves to inhibit cholesterol synthesis in the liver. 7. Note that oxidized LDL plays a role in the development of atherogenesis. B. Fatty Acids: Structure and Nomenclature 1. Be familiar with ? and ? (or n) systems for denoting the position of the double bond in unsaturated fatty acids. If given the structure of a fatty acid, be able to denote the position of the double bond(s) using both systems, OR if given the designation (e.g. 16:1n7) be able to draw the structure of the fatty acid. Given the w or n designation for a fatty acid, identify its parent fatty acid. 2. If given the systematic name of a fatty acid (e.g. hexadecanoic acid) indicate the chain length, common name, degree of saturation and major food source(s) of this fatty acid. OR if told the chain length, degree of saturation or major food sources, be able to give the name of a fatty acid which fits this category (e.g. A 16-carbon fatty acid = hexadecanoic acid). Review Table 5.1. 3. Distinguish between cis and trans configurations around the double bond. What conditions favor the conversion of cis to trans, and what are the implications of this conversion for : a. melting point of fatty acids, and b. utilization of fatty acids by humans? C. Lipid Metabolism 1. For each pathway: refer to objectives for part III-A 2. Specific points to consider about individual pathways: a. Fatty acid synthesis (lipogenesis) 1) Describe how acetyl-CoA is transported from mitochondria to cytoplasm so that it can be used for lipogenesis. 2) Note that the hexose monophosphate pathway is the major source of NADPH+H+ for lipogenesis. 3) Recognize that biotin plays a role in carboxylation reactions (e.g. it is a prosthetic group for acetyl CoA carboxylase). 4) Note that one of the key components of the fatty acid synthase system is acyl carrier protein (ACP). 5) Know the major tissues in which de novo lipogenesis occurs. 6) Understand the limitation that human enzymes have in terms of the synthesis of unsaturated fatty acids (can't introduce a double bond past the ? 9 position). b. Essential fatty acids (EFA) and eicosanoid synthesis -linolenic are considered essential fatty acids. 2) Recognize that arachidonic acid can be synthesized from linoleic acid. 3) List the functions of the EFA and the major symptoms of an EFA deficiency. 4) Eicosanoids (prostaglandins, thromboxanes, and leucotrienes) a) Note which eiconsanoids are synthesized from arachidonic acid via: 1. the cyclooxygenase pathway or 2. the lipoxygenase pathway. b) Give examples of the biological actions of the eiconsanoids. c) Discuss the mechanism of action of drugs like aspirin in relation to the eicosanoids. 5) Discuss the possible role of n-3 fatty acids (i.e. ?-linolenic acid) in the prevention of heart disease. c. Oxidation of fatty acids (?-oxidation) 1) Discuss significance of activation step. 2) Calculate #ATP's formed (and know why) for the complete oxidation of fatty acids to CO2 based on number of carbons in fatty acids. 3) Describe role of carnitine in getting fatty acids into the mitochondria. d. Formation of ketone bodies 1) Name the three ketone bodies. 2) Describe the main steps in the formation of ketone bodies and the conditions under which they are formed. 3) Note that while the liver synthesizes ketone bodies it cannot metabolize them. 4) State the purpose or function of ketone bodies in tissues like brain (during adapted fast) and muscle. rgf09
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