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UNE Medical Biochemistry Final Exam 2025 | University
Of New England | Featuring Topics such as Metabolic
Pathways, Enzymatic Function, Bioenergetics,
Carbohydrate and Lipid Metabolism, and Protein
Structure
Which of the following lipoproteins illustrated below would you most likely be associated with ApoB48? 1 2 3 4 ---------CORRECT ANSWER----------------- 1 A 33-year-old female 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? Chylomicrons VLDL
HDL
LDL
IDL ---------CORRECT ANSWER-----------------VLDL
A 45-year-old male is found to have elevated serum triglycerides (> 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? LDLs and adipocyte lipid droplets High-density lipoproteins (HDLs) and LDLs Chylomicrons and VLDLs Chylomicron remnants and High-density lipoproteins (HDLs) VLDLs and LDLs ---------CORRECT ANSWER-----------------Chylomicrons and VLDLs A patient with an insulinoma has high circulating levels of insulin. This will result in a(n): Upregulation of the gene for HMG-CoA reductase Inhibition of lipoprotein lipase Downregulation of the gene for 7 α-hydroxylase Stimulation of intracellular hormone-sensitive lipase ---------CORRECT ANSWER----- ------------Upregulation of the gene for HMG-CoA reductase
They are packaged into chylomicrons They are reabsorbed in the ileum They are digested by pancreatic lipase ---------CORRECT ANSWER-----------------They are reabsorbed in the ileum Elevated cholesterol can enhance bile acid synthesis through which of the following mechanisms? Inhibition of Cholesterol esterase Increasing the activity of 7 α-hydroxylase Inhibition of 12 α-hydroxylase Increasing activity of HMG-CoA Reductase ---------CORRECT ANSWER----------------- Increasing the activity of 7 α-hydroxylase What is the purpose of cholesterol esterification within the cell? (The conversion of cholesterol to cholesteryl-ester) Esterification traps cholesterol in the cell Esterification is the first step in the synthesis of cortisol This modification makes cholesterol more soluble in the plasma membrane. This modification does not change the chemical properties of cholesterol --------- CORRECT ANSWER-----------------Esterification traps cholesterol in the cell
Dietary cholesterol is primarily transported in the body by which of the following lipoproteins? LDL VLDL Chylomicron HDL ---------CORRECT ANSWER-----------------Chylomicron Which of the following is the regulatory enzyme in cholesterol synthesis? HMG-CoA synthase HMG-CoA reductase Acetyl CoA carboxylase Carnitine palmitoyl transferase I (CPTI) ---------CORRECT ANSWER----------------- HMG-CoA reductase Ketogenesis is regulated by the rate of several other processes. Which of the following would decrease the rate of ketone body synthesis? Increased flux through the TCA cycle. Increased β-oxidation Increased lipolysis Increased transport of FFA across the mitochondrial membrane ---------CORRECT ANSWER-----------------Increased flux through the TCA cycle.
Conversion of cytosolic oxaloacetate to malate Transportation of mitochondrial acetyl-CoA into the cytosol Assembly of the fatty acid chain Carboxylation of acetyl-CoA ---------CORRECT ANSWER-----------------Carboxylation of acetyl-CoA Which of the following enzymes generates NADPH? Pyruvate Carboxylase Acetyl-CoA carboxylase Malic enzyme Citrate lyase Pyruvate dehydrogenase ---------CORRECT ANSWER-----------------Malic enzyme 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? Succinyl-CoA Acetyl-CoA Acyl-CoA Malonyl-CoA ---------CORRECT ANSWER-----------------Malonyl-CoA
Which of the following lipoproteins illustrated below is most consistent with an LDL? 1 2 3 4 ---------CORRECT ANSWER----------------- 3 Which of the following enzymes is responsible for transferring triacylglycerol from VLDL to HDL in exchange for cholesterol? Microsomal transfer protein CEPT (Cholesteryl ester transfer protein) Phosphatidylcholine:cholesterol acyltransferase (PCAT, aka LCAT) Lipoprotein Lipase ---------CORRECT ANSWER-----------------CEPT (Cholesteryl ester transfer protein) Cholesterol stimulates the activity of which of the following proteins required for bile acid synthesis? 12 α-hydroxylase Cholesterol esterase 7 α-hydroxylase HMG-CoA Reductase ---------CORRECT ANSWER-----------------7 α-hydroxylase
Elevated levels of arginine Elevated levels of citrulline Decreased levels of carbamoyl phosphate Decreased levels of ammonia ---------CORRECT ANSWER-----------------Decreased levels of carbamoyl phosphate A deficiency in which of the following enzymes will not result in an increase in orotic acid? Argininosuccinate lyase N-acetyl glutamate synthetase Ornithine transcarbamylase Argininosuccinate synthetase ---------CORRECT ANSWER-----------------N-acetyl glutamate synthetase Which of the following enzymes is correctly paired with its activator? arginase; NADH Carbamoyl phosphate synthetase I; ATP Glutaminase; citrate N-acetyl glutamate synthetase; arginine ---------CORRECT ANSWER-----------------N- acetyl glutamate synthetase; arginine
The transamination of all amino acids requires which of the following cofactors? Pyridoxal phosphate (PLP) Thiamine N-acetyl glutamate Folate ---------CORRECT ANSWER-----------------Pyridoxal phosphate (PLP) In the fasted state, when glutamine enters the liver which of the following reactions occurs? pyruvate + glutamine → alanine; alanine aminotransferase ammonia + glutamate → glutamine; glutamine synthetase glutamine → ammonia + glutamate; glutaminase ammonia + glutamine → glutamate; glutamate dehydrogenase ---------CORRECT ANSWER-----------------glutamine → ammonia + glutamate; glutaminase Which of the following non-essential amino acids is synthesized as part of the urea cycle? Arginine Glutamine Asparagine
Tryptophan synthase Homogentisate oxidase Phenylalanine hydroxylase Tyrosine aminotransferase ---------CORRECT ANSWER-----------------Phenylalanine hydroxylase A deficiency in the ability to convert phenylalanine to tyrosine may result in a further deficiency of both _________________ and ________________. Glutamine and glutamine Serotonin and melatonin Acetylcholine and choline Cysteine and homocysteine Norepinephrine and epinephrine ---------CORRECT ANSWER----------------- Norepinephrine and epinephrine Metabolism of _____________________ leads to the synthesis of __________________. Tyrosine ; serotonin Glycine ; epinephrine Tryptophan ; melatonin Alanine ; homocysteine
Threonine ; norepinephrine ---------CORRECT ANSWER-----------------Tryptophan ; melatonin In the case of a deficiency in phenylalanine hydroxylase which of the following amino acids will become essential? Cysteine Tryptophan Homocysteine Methionine Tyrosine ---------CORRECT ANSWER-----------------Tyrosine An elevation of homocysteine and a decrease in cysteine would most likely be present due to which of the following deficiencies? Cobalamin deficiency Tetrahydrobiopterin (BH4) deficiency Loss of function of cystathionine-β synthase Loss of function of methionine synthase ---------CORRECT ANSWER----------------- Loss of function of cystathionine-β synthase A 52-year-old male sought medical attention due to the progressive appearance of hyperchromic (hyperpigmented) papules on the edge of the second finger of
4 ---------CORRECT ANSWER----------------- 4 - +-+
The chemical reaction below (Figure 1) depicts the conversion of phenylalanine to tyrosine. Select the enzyme that is responsible for the conversion of PHE to TYR. Figure 01 Phenylalanine (PHE) Tyrosine (TYR) Phenylalanine hydroxylase Phenylalanine N-methyltransferase Phenylalanine decarboxylase Phenylalanine reductase Phenylalanine O-demethylase ---------CORRECT ANSWER----------------- Phenylalanine hydroxylase Which of the following enzymes is used directly in the synthesis of dTMP (thymidine)? Thymidylate synthase Aspartate transcarbamoylase Dihydrooratase Carbamoyl phosphate synthetase II (CPSII) ---------CORRECT ANSWER----------------- Thymidylate synthase
Inhibition of the folate cycle by 5-fluorouracil will decrease the synthesis of which of the following metabolites? ATP dGMP dUMP dTMP ---------CORRECT ANSWER-----------------dTMP In pyrimidine synthesis, carbamoyl phosphate synthetase II (CPSII) can be allosterically activated by which of the following compounds? 5 - phosphoribosyl pyrophosphate (PRPP) Carbamoyl phosphate Uridine triphosphate (UTP) Adenosine triphosphate (ATP) ---------CORRECT ANSWER----------------- 5 - phosphoribosyl pyrophosphate (PRPP) A 47-year-old male complains of pain in his left big toe, which is obviously swollen and tender. The pain has been acute and a diagnosis of gout is made. Which of the following is involved in the pathophysiology of this patient's condition? Elevated uric acid
A newborn is suspected of a defect in nucleotide synthesis due to the elevation of orotic acid. It is determined there is no deficiency in orotate phosphoribosyltransferase. Based on this presentation, which of the following enzymes is most likely deficient? Carbamoyl phosphate synthetase II (CPSII) Thymidylate synthase Ornithine transcarbamylase Glutamyl amidotransferase ---------CORRECT ANSWER-----------------Ornithine transcarbamylase Methotrexate is a potent anticancer agent that starves dividing cells of deoxyribonucleotides through direct inhibition of which of the following processes? Degradation of purine bases to uric acid Deoxygenation of the ribose ring to produce deoxyribose for DNA Metabolism of folic acid Synthesis of purine bases Synthesis of thymidine ---------CORRECT ANSWER-----------------Metabolism of folic acid
Which of the following best describes why purines are recycled? They are required to a greater extent for DNA synthesis They are utilized to a greater extent when compared to pyrimidines The double ring structure is difficult to enzymatically break They cannot be endogenously synthesized ---------CORRECT ANSWER----------------- The double ring structure is difficult to enzymatically break The conversion of ribose bases into deoxy-bases will be occurring under which of the following conditions? In the fed state Under most conditions In the fasted state When cells are proliferating ---------CORRECT ANSWER-----------------When cells are proliferating Purine biosynthesis starts with the activation of a 5-carbon sugar. In this initial reaction, ribose 5-phosphate is converted into which of the following compounds? 5 - phosphoribosyl pyrophosphate (PRPP) 5 - methyl thymidine Glucose 6-phosphate
