UNE Biochem FINAL |83 Questions| With 100% Verified & Passed Solutions.

UNE Biochem FINAL |83 Questions| With 100% Verified & Passed Solutions. An individual goes to bed around 8 pm and doesn't wake up until 9 am the next morning. During this time, which of the following is the primary oxidizable substrate in the skeletal muscle? Free fatty acids Under fasted conditions as described above, the skeletal muscle and liver would be oxidizing free fatty acids as a means of producing ATP. A well, 2-year-old girl presents to the clinic with symptoms of a viral illness. Her parents report she has had bouts of vomiting and diarrhea over the last 24 hours. This morning they could barely wake her from her crib and she was very weak. Laboratory tests show low blood glucose (hypoglycemia) and elevated liver enzymes. There are no ketones present in her urine. The child is hospitalized and glucose is administered by I.V. Additional laboratory analysis showed elevated medium-chain fatty acyl carnitines in blood and 6-8 carbon dicarboxylic acids in the urine. Which of the following abnormalities is the most likely diagnosis for this child? Defect of medium-chain acyl-dehydrogenase This presentation is consistent with a deficiency in medium-chain acyl-dehydrogenase. The lack of ketones suggests a deficiency in β-oxidation and the presence of medium chain carnitines and dicarboxylic acids suggest products of omega-oxidation. The process of ketogenesis refers to the conversion of acetyl-CoA to which of the following compounds? D-3-hydroxybutyrate or β-hydroxybutyrate Ketogenesis is the process by which excess acetyl-CoA from β-oxidation is converted to the ketone bodies: D-3-hydroxybutyrate (β-hydroxybutyrate) and acetoacetate. During the fasted state, lipolysis is facilitated by the action of hormone sensitive lipase. This enzyme requires which of the following modifications for activation? Phosphorylation Glucagon will increase levels of lipolysis through the phosphorylation and activation of hormone sensitive lipase. ATP can be generated by many metabolic pathways in the body. Which of the following processes generates the most ATP? Fatty acid β-oxidation 7 NADH, 7 FADH2 and 8 acetyl-CoA are all produced by β-oxidation of a C16 fatty acid. This will generate 108 mol ATP/ mol palmitate. Under fasting conditions (ratio of insulin to glucagon 1), elevated glucagon will activate which of the following enzymes? Hormone sensitive lipase Glucagon will increase levels of lipolysis through the phosphorylation and activation of hormone sensitive lipase. An individual is on a hunger strike and has not eaten in 13 days. Which of the following best describes their metabolic state? The brain will be preferentially oxidizing ketones. Under conditions of excess fasting (i.e. starvation), the brain will begin to oxidize ketones as a primary fuel source reducing its reliance on glucose. An 11-year-old girl is brought to the emergency department by her father. He reports she has recently been very thirsty and needing to make frequent trips to the bathroom. At her soccer game today, she complained of lightheadedness and the symptoms did not resolve even after drinking a power beverage. A rapid dipstick test revealed glucose in her urine and further diagnostics were consistent with a diagnosis of type 1 diabetes. Evaluation of this girl's liver would reveal an increased rate of which of the following processes? Ketogenesis The description here is of type 1 diabetes which is consistent with a loss of insulin production. Therefore, fasted state metabolic pathways would be highly active contributing to hyperglycemia and ketogenesis. The other pathways listed would be active in the fed state or when insulin is high. Which of the following enzymes is correctly paired with its allosteric inhibitor? Acetyl-CoA carboxylase: palmitoyl-CoA The regulatory step in fatty acid synthesis is the synthesis of malonyl-CoA by acetyl-CoA carboxylase. This enzyme can be inhibited by fatty acyl-CoA . Elevated fatty acyl-CoA will also inhibit the tricarboxylate transporter and reduce citrate efflux from the TCA. A defect in the thioesterase subunit of fatty acid synthase would impair which of the following activities of the enzyme complex? Liberation of newly assembled palmitate from the enzyme Fatty acid synthase is a multimeric enzyme and the final and sixth enzyme in the chain is the thioesterase which will liberate the newly formed palmitate. Under fasting conditions, acetyl-CoA carboxylase will be inhibited by an increase in which of the following compounds? fatty acyl-CoA In fasting conditions when lipolysis is active, an increase in fatty acyl-CoA in the cell for the process of β-oxidation will decrease citrate efflux from the mitochondria and activity of acetyl-CoA carboxylase. An increase in the ratio of insulin to glucagon will increase the activity of which of the following enzymes (+ indicates activity is increased; - indicates activity is not increased by insulin)? Hormone sensitive lipaseAcetyl-CoA carboxylasePhosphofructokinase-2 (PFK2)Glycogen synthase 1+++- 2++-- 3+--- 4-+++ 4 When insulin is elevated fed state pathways will be persistent. This will include the activation of acetyl-CoA carboxylase through dephosphorylation. PFK2 in glycolysis and glucagon synthase will also be active under these conditions. Which of the following is the regulated step of lipogenesis in eukaryotes? Carboxylation of acetyl-CoA The regulatory step in fatty acid synthesis is the synthesis of malonyl-CoA by acetyl-CoA carboxylase. This reaction uses CO2 and biotin to add carbon to cytosolic acetyl-CoA. Which of the following is the regulatory enzyme for fatty acid synthesis? Acetyl-CoA carboxylase The regulatory step in fatty acid synthesis is the synthesis of malonyl-CoA by acetyl-CoA carboxylase. This reaction uses CO2 and biotin to add carbon to cytosolic acetyl-CoA. 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? Malonyl-CoA Initially, acetyl-CoA is bound to the acyl carrier protein (ACP), after this all subsequence 2 carbon units are added via malonyl-CoA Under conditions when 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? Pyruvate carboxylase Pyruvate carboxylase will synthesize oxaloacetate in the mitochondria which will assist in the synthesis of citrate. Citrate can be shuttled out of the mitochondria to be used for cytosolic fatty acid synthesis. A 16-year-old woman presents to her primary care physician for a follow up visit. At her initial visit, 3 months ago, her serum cholesterol was 255 mg/dL (above normal). Today her serum triglycerides are reported to be 260 mg/dL (above normal) . She finds this very disappointing as she started a strict dietary regime reducing all fats and cholesterol, replacing them with a high carbohydrate diet. You tell her that high carbohydrate diets can increase serum triglyceride levels in some individuals. This can be attributed to an increase in the synthesis of which of the following lipoproteins? VLDL Increase in dietary carbohydrates can result in increased de novo fatty acid synthesis and therefore an increase in VLDL production. Excess dietary carbohydrates are metabolized to acetyl-CoA that enters the TCA cycle. In the mitochondria, excess citrate will be shuttled out of the organelle and used for fatty acid synthesis in the liver. Which lipoprotein is responsible for the process of reverse cholesterol transport (the movement of cholesterol from the peripheral tissues back to the liver)? HDL HDL is responsible for moving cholesterol from peripheral tissues to the liver. In reverse cholesterol transport, HDL interacts with the ABC transporters to move cholesterol from the cell to the HDL. This also requires the activity of which of the following enzymes? Lecithin cholesterol acyltranferase (LCAT) Esterification of cholesterol is a process needed in increase hydrophobicity to trap cholesterol in the cell or HDL. ACAT is primarily responsible for trapping cholesterol in the cell whereas LCAT is found in circulation associated with HDL. The interaction of chylomicrons with lipoprotein lipase is stimulated by which of the following Apo proteins? ApoC II ApoCII is acquired from an interaction with HDL and is required to activate lipoprotein lipase. Phospholipids are also required for this activation. Lecithin:cholesterol acyl tranferase (LCAT) is a plasma enzyme associated with HDL particles. Which of the following best describes its role in cholesterol transport? Esterifies cholesterol to trap it in HDL particles Esterification of cholesterol is a process needed in increase hydrophobicity to trap cholesterol in the cell or HDL. ACAT is primarily responsible for trapping cholesterol in the cell whereas LCAT is found in circulation associated with HDL. HDL particles interact with VLDL particles to exchange cholesterol ester for triacyclglycerols. Which of the following enzymes is responsible for this process? Cholesterol ester transfer protein (CETP) CETP is responsible for this exchange between the two lipoproteins. A 45-year-old man is found to have an elevated serum triglycerides of 730mg/dL. He tells you he forgot to fast before his visit and he ate a full breakfast of bacon and eggs before the labs were drawn. Which of the following lipoproteins would be the largest contributors to a measurement of plasma triglycerides in this situation? Chylomicrons and VLDLs