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UNE BIOCHEMISTRY UNIT 3
QUESTIONS AND ANSWERS 2023
Which of the following lipoproteins distributes dietary lipids? - answer chylomicron The interaction of chylomicrons with lipoprotein lipase is stimulated by which of the following Apo proteins? - answer ApoC II Nascent chylomicrons are synthesized in which tissue? - answer Intestine Bile salts are synthesized from cholesterol and are used for the emulsification of dietary lipids. What is the primary fate of bile salts during digestion? - answer They are reabsorbed in the ileum Nascent chylomicrons interact with HDL particles and obtain which of the following Apo protiens? - answer ApoCII and ApoE The activity of pancreatic lipase is inhibited by which of the following compounds? - answer Bile salts Which of the following statements regarding lipid digestion and absorption is true? A. The products of lipid digestion travel in the circulatory system in the form of micelles. B. The products of lipid digestion diffuse into capillaries in the vicinity of the intestinal epithelium. C. Pancreatic lipase emulsifies lipids.
D. The products of lipid digestion are resynthesized into triacylglycerols in intestinal epithelial cells. E. In the absence of bile salts, no digestion of lipids would - answer The products of lipid digestion are resynthesized into triacylglycerols in intestinal epithelial cells. Under fasting conditions (Ratio of insulin to glucagon <1), elevated glucagon will activate which of the following enzymes? - answer Hormone sensitive lipase VLDL particles are characterized by which of the following apoproteins? - answer Apo B 100 An increase in insulin leads to which of the following metabolic shifts? - answer Acetyl CoA carboxylase will become dephosphorylated and active Biotin is a cofactor required for which of the following enzymes? - answer A and B (Acetyl CoA carboxylase and Pyruvate carboxylase) The first step in fatty acid synthesis is the formation of ________ from acetyl CoA and carbon dioxide. - answer malonyl CoA Insulin increases the activity of all of the following enzymes except: - answer Hormone sensitive lipase Which of the following is the regulatory enzyme for fatty acid synthesis? - answer AcetylCo A carboxylase Which of the following is the regulated step of fatty acid synthesis in eukaryotes? A. Carboxylation of acetyl CoA
D. FADH2 - answer NADPH During the fasted state, lipolysis is facilitated by the action of hormone sensitive lipase. This enzyme requires which of the following post - translational modification for activation? - answer Phosphorylation Adiponectin is secreted from adipocytes. One of the primary roles of adiponectin is to activate AMPK in skeletal muscle which enhances the activity of which of the following pathways? - answer β oxidation When the processes of glucose oxidation is elevated, the acetyl CoA produced will allosterically activate which of the following enzymes leading to an increase in the production of oxaloacetate? - answer Pyruvate carboxylase The process of ketogenesis refers to the conversion of acetyl CoA to which of the following compounds? - answer β-hydroxybutyrate The transport of newly synthesized fatty acids to the adipose requires all of the following except: A. Interaction of ApoCII with lipoprotein lipase B. Transport of triacylglycerols from the liver using VLDLs C. Synthesis of triacylglycerol using glycerol 3-phosphate D. Carnitine to shuttle the fatty acids out of the mitochondria - answer Carnitine to shuttle the fatty acids out of the mitochondria
In the case of a deficiency of biotin, which of the following enzymes required for fatty acid synthesis will be impaired? - answer Acetyl CoA carboxylase Which of the following compounds is the substrate for the synthesis of coritsol? A. Cholesterol B. Free fatty acids C. Glucose D. Amino acids - answer Cholesterol Under cellular conditions when cholesterol is low, which of the following is a true statement regarding the sterol response element binding protein? - answer It will be associated with the the sterol response element (SRE) in the DNA HDL particles are characterized by the presence of which apoprotein: A. Apo B 100 B. Apo B C. ApoA D. ApoCII - answer ApoA Which of the following is the regulatory enzyme in cholesterol synthesis?
Secondary bile salts are generated by bacterial modification of primary bile salts in the intestinal lumen. These modification have which of the following impacts on bile salt solubility? A. decrease solubility B. increase solubility C. have no change on solubility - answer decrease solubility The uptake of LDL increases intracellular cholesterol levels. This has which of the following impacts on de novo cholesterol synthesis? A. Increases activity of HMGCoA reductase B. Increases degradation of HMGCoA reductase C. Dephosphorylation of HMGCoA reductase. D. Increases movement of SREBP:SCAP to the golgi - answer Increases degradation of HMGCoA reductase LCAT esterifies cholesterol. This process is required for which of the following processes? A. To trap cholesterol in HDL particles B. Movement of cholesterol out of the cell
C. Degradation of cholesterol D. Synthesis of cholesterol derivatives - answer To trap cholesterol in HDL particles A deficiency in the LDL receptor will result in which of the following? A. A decrease in intracellular cholesterol B. A decrease in circulating LDLs C. An decrease in de novo cholesterol synthesis D. A decrease in fatty acid synthesis - answer A decrease in intracellular cholesterol Which of the following terms is used to define macrophages that are filled with oxLDL? A. Foam cells B. LDL C. Oxidized endothelial cell D. Endothelial cell - answer foam cells Which of the following is a true statement, concerning HMGCoA reductase?
D. SREBP:SCAP will be bound to the endoplasmic reticulum - answer SREBP:SCAP will be bound to the endoplasmic reticulum Under fasted condition, (glucagon is elevated), which of the following enzymes will be phosphorylated and inactive? - answer HMGCoA reductase In the reaction catalyzed by cholesterol ester transfer protein (CETP), the VLDL particle receives which of the following compounds from HDL particles? - answer Cholesterol-ester Statins are drugs that inhibit cholesterol synthesis by inhibition of the regulatory enzyme for this process. Which of the following enzymes is the direct target of statins? - answer HMGCoA reductase Which lipoprotien is responsible for the process of reverse cholesterol transport (the movement of cholesterol from the peripheral tissues back to the liver)? - answer HDL Cholesterol is a substitute for all of the following compounds except: - answer guanine HDL particles interact with VLDL particles to exchange cholesterol ester for triacylglyerols. Which of the following enzymes is responsible for this process? - answer Cholesterol ester transfer protein (CETP) The skeletal muscle primarily provides substrate for gluconeogenesis through which of the following processes? A. β-oxidation B. Protein catabolism C. Lipolysis
D. Glycogenolysis - answer Protein catabolism Which of the following enzymes is used by the gluconeogenic pathway but not the glycolytic pathway? A. phosphoenolpyruvate carboxykinase B. triose phosphate isomerase C. pyruvate kinase D. hexokinase E. glyceraldehyde-3-phosphate dehydrogenase - answer phosphoenolpyruvate carboxykinase Which of the following compounds allosterically activates pyruvate carboxylase? A. Malonyl CoA B. Pyruvate C. Acetyl CoA D. Oxaloacetate - answer Acetyl CoA The process of gluconeogenesis primarily takes place in which of the following tissues?
D. protein catabolism - answer hepatic glycogenolysis If unregulated, which of the following pairs of enzymes would represent a futile cycle? A. pyruvate kinase and pyruvate carboxylase B. pyruvate carboxylase and phosphoenolpyruvate carboxykinase C. pyruvate kinase and fructose-1,6-bisphosphatase D. glucose-6-phosphatase and phosphofructokinase 1 E. fructose-1,6-bisphosphatase and phosphofructokinase 1 - answer fructose-1,6- bisphosphatase and phosphofructokinase 1 Ethanol metabolism: A. decrease the synthesis of fatty acids B. increases the ratio of NADH/NAD+ C. increases the production of glucose D. decrease the ratio of NADH/NAD+ - answer increases the ratio of NADH/NAD+ The first step in ethanol metabolism is in the cytosol and generates which of the following products?
A. NAD+
B. acetaldehyde C. Acetyl CoA D. acetate - answer acetaldehyde Acetate generated from ethanol metabolism can be directly converted to _____________________ which can be oxidized in the TCA cycle. A. Acetone B. Acetyl CoA C. beta-hydroxybuterate D. Acetalydehye - answer Acetyl CoA Increase in ethanol consumption leads to an increase in the ratio of NADH/NAD+. This promotes the conversion of pyruvate to which of the following compounds? A. acetylCoA B. oxaloacetate C. alanine
D. pyruvate carboxylase and phosphoenolpyruvate carboxykinase E. pyruvate kinase and fructose-1,6-bisphosphatase - answer fructose-1,6-bisphosphatase and phosphofructokinase 1 Which of the following is the primary metabolic fate of acetate generated from ethanol metabolism? A. It is toxic and oxidized by the liver B. It is volatile and blow off in the lungs C. It is oxidized directly by the TCA cycle in the liver D. It is converted to acetyl CoA by peripheral tissues - answer It is converted to acetyl CoA by peripheral tissues Both gluconeogenesis and fatty acid β oxidation are required for homeostasis in the fasted state. Which of the following statements is false with regards to how these pathways interact? A. Glycerol from lipolysis can be used as a substrate for gluconeogenesis B. Acetyl CoA is a substrate required for gluconeogenesis C. Acetyl CoA from fatty acid oxidation stimulates pyruvate carboxylase D. β oxidation provides ATP for gluconeogenesis - answer Acetyl CoA is a substrate required for gluconeogenesis
Which of the following hormones initiates skeletal muscle catabolism to provide substrate for gluconeogenesis? A. cortisol B. insulin C. epinephrine - answer cortisol In a fasted individual, excessive alcohol consumption will contribute to all of the following except: A. Increased lactate production B. Increased ketogenesis C. Increased ratio of NADH/NAD+ D. Increased chylomicron secretion - answer Increased chylomicron secretion Ethanol metabolism increases the ratio of NADH/NAD+. This leads to all of the following metabolic consequences except: A. Conversion of pyruvate to lactate B. Inhibition of lipolysis
A. mitochondria; acetaldehyde B. cytosol; acetate C. mitochondria; acetone D. cytosol; acetaldehyde - answer cytosol; acetaldehyde During fatty acid synthesis, after the initial step involving acetyl CoA, the fatty acid chain is elongated by the addition of which of the following compounds? A. Acetyl CoA B. Malonyl CoA C. Acyl CoA D. Succinyl CoA - answer Malonyl CoA Excessive alcohol consumption can lead to the presentation of hypoglycemia. This is primarily caused by which of the following? A. A decrease in substrates required for gluconeogenesis B. A decrease in ketogenesis C. A decrease in acetyl CoA
D. A decrease in lipolysis - answer A decrease in substrates required for gluconeogenesis What is the primary fuel oxidized in the liver (to generate ATP) in the fasted state? A. free fatty acids B. ketones C. lactate D. glucose - answer Free fatty acids The elevated levels of NADH/NAD generated by alcohol metabolism inhibit all of the following except: A. alpha ketoglutarate dehydrogenase B. pyruvate dehydrogenase kinase C. malate dehydrogenase D. isocitrate dehydrogenase - answer pyruvate dehydrogenase kinase Which of the following proteins is responsible for the transfer of ApoB48 to nascent chylomicrons before secretion into circulation? A. Microsomal transfer protein (MTP)
