1/10
A 46-year-old man comes to the emergency department due to recurrent nosebleeds. When interviewed tor additional history, he becomes belligerent and uncooperative. The patient has a history of alcohol abuse and chronic mental illness. He has been placed in homeless shelters on multiple occasions but has not remained there for any prolonged periods. Physical examination shows swollen gums,scattered ecchymoses,and hyperkeratosis. He also has a chronic ulcer on the left lower extremity that does not appear to be infected. Which of the following mechanisms accounts for this patient's examination findings?
- Abnormal oxidative decarboxylation of ketoacids
- Abnormal proline hydroxylation
- Abnormal transamination
- Deficient methionine synthesis
- Diminished synthesis of purines
2/10
An infant born to a 23-year-old female is diagnosed with an inherited condition that results in impaired transport of ornithine from the cytosol to the mitochondria. Restriction of which of the following substances in the diet can improve this patient's condition?
- Fatty acids
- Protein
- Cholesterol
- Monosaccharides
- Disaccharides
- Purines
3/10
3. A diagram illustrating the DNA replication process is shown below.which of the points marked by letters represents the site of action of helicase in the following diagram?
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- A
- B
- C
- D
- E
4/10
A 2-year-old male demonstrates periodic lethargy, vomiting, and confusion. Laboratory testing reveals increased blood ammonium levels during these episodes as well as markedly increased urine orotic acid excretion. Which of the following enzymes is most likely to be deficient in this patient?
- Carbamoyl phosphate synthase I
- Ornithine transcarbamoylase
- N-acetylglutamate synthase
- Hypoxanthine-guanine phosphoribosyltransferase
- Adenosine deaminase
5/10
A 14-year-old boy is undergoing evaluation for conductive hearing loss. He has a history of multiple fractures involving his arms, legs, and ribs, most of which occurred following minor trauma. Genetic analysis shows a mutation involving the type I collagen a2-chain and the physician diagnoses him with osteogenesis imperfecta. The complex process of collagen biosynthesis begins within osteoblasts and continues in the extracellular space. Which of the following processes occurs outside of the osteoblast during coNagen synthesis?
- C-terminal propeptide removal
- Cleavage of the N-terminal signal peptide
- Glycosylation of hydroxylysine residues
- Interchain C-terminal disulfide bond formation
- Proline residue hydroxylation
- Triple helix formation
6/10
A 34-year-old man is brought to the emergency department with severe headache and blurry vision. His symptoms began suddenly after having lunch at a new Italian deli in his neighborhood. The patient says he 'ate a sandwich with lots of fancy meats and cheeses' and drank an iced tea. His past medical history is significant for severe, atypical depression. He has no known medication or food allergies. His blood pressure is 210/130 mm Hg and heart rate is 110/min. On physical examination, he appears tremulous and diaphoretic. The medication used to treat this patient's depression most likely affects which of the following steps of monoamine neurotransmission?
- Monoamine degradation
- Binding to postsynaptic receptors
- Presynaptic non-selective monoamine uptake
- Presynaptic selective norepinephrine uptake
- Presynaptic selective serotonin uptake
7/10
A 34-year-old woman comes to the physician with abdominal pain and melena. She also complains of progressive fatigue and a 5 kg (11 lb) weight loss over the last 2 months. She has a strong family history of colon, endometrial, and ovarian cancer. Colonoscopy shows a protuberant, friable mass in the ascending colon, and biopsy is diagnostic for colon adenocarcinoma. Genetic analysis confirms a mutation consistent with Lynch syndrome (hereditary nonpolyposis colon cancer). Which of the following is most likely responsible for the development of colon cancer in this patient?
- Nucleotide mismatches that escape repair
- Covalent bonds between adjacent pyrimidines
- Insertion of abnormal bases (eg, uracil) into DNA
- Empty sugar-phosphate residues in the DNA molecule
- Double-strand breaks in DNA
8/10
Microbiologists are investigating sugar metabolism in wild-type and mutant strains of Escherichia coll. Both strains are found to grow viable colonies on lactose-containing media. Each strain is then cultured on a new growth medium containing only glucose. Representative colonies of each strain from the new media undergo Western blot processing using a fluorescently labeled probe specific for β-galactosidase. Wild-type bacterial colonies are found to contain only trace quantities of β-galactosidase. However, the mutant colonies express significant amounts of β-galactosidase. Further analysis reveals that the variant strain contains a mutation that inhibits the binding of a certain protein to its regulatory sequence. In which of the following locations did this mutation most likely occur?
- Activator protein (CAP) binding site
- Operator locus
- Promoter region
- Activator protein (CAP) gene
- RNA polymerase cistron
9/10
A 23-year-old male is brought to the emergency room with confusion. He is found to have a blood glucose level of 38 mg/dL. On further investigation, it is discovered that his liver cells have a high level of NADH. Which of the following statements is most likely to be true?
- This patient has been consuming large volumes of alcohol lately
- His urine will probably test positive for cocaine
- He suffers from diabetes mellitus type II
- He takes amitriptyline regularly
- He has been exposed to infected body fluids recently
10/10
An infant who fails to gain weight has no enteropeptidase activity on the surface of her duodenal epithelium. Formation of which of the following substance is most likely impaired by this patient's condition?
- Lipase
- Pepsin
- Amylase
- Trypsin
- Lactase
- Secretin
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