NBME Biochemistry Shelf Exam 2023 Questions and Answers

What neurotransmitter stimulates release of epinephrine from adrenal medulla? - Answer- acetylcholine What is a metabolite if epinephrine that suggests epi-secreting carcinoma? What is another assoc symptom? - Answer- metanephrine; assoc with HBP What does acetazolamide (carbonic anhydrase ib) treat? - Answer- glaucoma, epilepsy, altitude sickness, congestive heart failure can cause dehydration Sickle cell anemia is due to... - Answer- pt mutation of Glu -> val What is a major neurotransmitter amino acid? - Answer- Glu HA protein of influenza binds to - Answer- cytokine receptors What is a reducing-sugar test? - Answer- Tests for aldo-keto sugars What is omeprazole? - Answer- proton pump ib Name some GAG's. - Answer- heparin sulfate, chondroitin sulfate, What type of reaction is glucuronidation? - Answer- oxidation In Marfan's syndrome, what part of fibrillin's protein structure is affected? - Answer- primary structure What are the symptoms of Huntington's disease? - Answer- anxiety, uncontrollable mvmts, slurring of speech, difficulty focusing or concentrating; caused by triple repeat expansion What is Chediak-Higashi syndrome? - Answer- phagocyte deficiency -> hypergammaglobulinemia, significant neutropenia, In exposure to carbon monoxide or cyanide, which way does the ox sat curve shift? - Answer- to the L; increased affinity at low pO_2 What is pralidoxime chloride? - Answer- reactivate acetylcholinesterase Wernicke encephalopathy - Answer- inadequate thiamine; confusion, ophthalmoplagia (nystagmus) What is the function of lactase? - Answer- beta(1->4) galactosidase; cleaves Gal from Glu How is fructose absorbed? - Answer- via sodium-independent transporter What sugar enzymes are found on the intestinal brush border? - Answer- sucrase, lactase, maltase, isomaltase Orlistat - Answer- ib pancreatic and gastric lipase; leads to reduced fat digestion What is fiber? - Answer- glucose beta(1->4) glucose bonded sugar; body does not have beta(1-4) endoglucosidase enterokinase - Answer- activates trypsinogen; trypsin activates chymotrypsin, procolipase, procarboxypeptidase, and proelastase arsenic - Answer- pyruvate dehydrogenase ib; smell of garlic Which GLUT is insulin-dependent? - Answer- GLUT4; found in muscle & adipose What is the role of F2,6BP? - Answer- role player for insulin; increases glycolysis for FA synth and glycogen synthesis What is significant about glucokinase? - Answer- K_m is above fasting concentration, V_max is very high What promotes lactate buildup? - Answer- ^ NADH/NAD+ Where does lactate build up? - Answer- eyes, testes, RBC's What is the rate-limiting step of glycolysis? - Answer- PFK, allosterically activated by F2,6BP Def in pyr kinase leads to... - Answer- 2,3BPG, G6P elevation due to ^ PEP What steroid can be used to treat beta-blocker overdose? - Answer- glucagon Which form of aldolase is liver-specific? - Answer- B triose phosphate isomerase - Answer- G3P <-> DHAP; DHAP - component of glycerol phosphate shuttle What TCA step makes GTP? - Answer- succinate thiokinase What TCA step makes FADH? - Answer- succinate dehydrogenase What is the only membrane-bound enzyme in TCA? - Answer- succinate dehydrogenase What characterizes succinate? - Answer- dicarboxylic acid pyruvate carboxylase - Answer- pyr -> OAA; requires biotin Rotenone - Answer- inhibits complex I of ETC antimycin - Answer- ib complex II, succinate dehydrogenase Which ETC complex contains heme? - Answer- cytochrome oxidase What is Kearns-Sayre syndrome? - Answer- mutation in complex II What is the electron donor for Complex I? - Answer- NADH superoxide dismutase - Answer- superoxide to peroxide catalase - Answer- peroxide to water Pompe disease - Answer- loss of lysosomal glucosidase activity Cori's disease - Answer- loss of alpha-1,6 glucosidase activity, debranching enzyme von Gierke's disease - Answer- glucose-6-phosphatase def; glu trap McArdle's disease - Answer- m specific glycogen phosphorylase def caffeine - Answer- ib cAMP phosphodiesterase What is amylo-4,6-transferase? - Answer- branching enzyme for glycogen synth What enzyme can be both phosphorylated and attached to calcium ions to be active? - Answer- glycogen phosphorylase kinase When is glycogen depleted in a fast? - Answer- 30 hr When is gluconeogenesis the major pathway for energy? - Answer- 18-20 hr of fast avidin, found in egg whites - Answer- binds to biotin, decreases carboxylase function Cushing's syndrome - Answer- ^ glucocorticoids -> ^ PEPCK -> ^ PEP -> hyperglycemia Sly syndrome (mucopolysaccharidosis) - Answer- def in beta-glucuronidase classical galactosemia - Answer- def in galactose 1-P uridylyltransferase; can cause sepsis, hypoglycemia, phosphate sequestration symptoms of def in G6PDH - Answer- hemolysis in oxidative environment I-cell disease - Answer- N-acetylglucosamine 1-P transferase; assoc with gingival hypertrophy, devo delays Conversion of glucose to sorbitol is accomplished by... - Answer- aldose reductase Where are fatty acids synthesizedd? - Answer- cytosol What is an essential fatty acid? - Answer- linoleate, diunsat FA Zellweger syndrmoe - Answer- peroxisome malforation, ^ VLCFA, increase in plasmalogens as well def in medium-chain acyl CoA dehydrogenase - Answer- results in many short-chain dicarboxylic acids from omega-ox w/o beta-ox carnitine - Answer- transports acyl groups across inner mito membrane Hurler's syndrome - Answer- def in alpha-iduronidase Morquoi syndrome - Answer- galactose-6-sulfatase def Hunter syndromw - Answer- iduronate sulfatase def Sanfilippo A syndrome - Answer- heparan sulfamidase Homocystinuria - Answer- def in cystathionine synth; meth accum Argininosuccinate lyase - Answer- enzyme in urea cycle; def can lead to hyperammonemia role of glutamate in nitrogen metablism - Answer- fix ammonia for transport What is the metabolic product of Phe breakdown? - Answer- fumarate and acetoacetate Product of Asp, Asn breakdown - Answer- OAA product of valine, threonine, isoleucine, methionine breakdown - Answer- succinyl-CoA hyperammonemia and elevated arginine is indicative of... - Answer- defect in arginase (urea cycle disorder) What amino acids are in highest concentration post-absorption after meal? - Answer- alanine and glutamine (main ammonium transporters) what can lead to liver ascites? - Answer- def albumin synth; kwashiorkor - Answer- caloric sufficiency with protein deficiency cachexia - Answer- weight loss, muscle wasting despite nutritional sufficiency marasmus - Answer- overall nutritional deficiency cosyntropin evaluates - Answer- cortisol levels low sodium and reduced urine osmolality resulting from a pulmonary mass is indicative of... - Answer- syndrome of inappropriate ADH (SIADH) lipocortin - Answer- ib phospholipase A2 what is central obesity indicative of? - Answer- hypercortisolemia Cushing syndrome v. Cushing disease - Answer- syndrome - ^ cortisol by adrenal tumor disease - ^ ACTH by pituitary tumor Conn syndrome - Answer- ^ aldosterone -> hypertension and hypokalemia morphne has a similar function to... - Answer- endorphin What can inhibit the release of prolactin? - Answer- Dopamine Hyperthyroidism - Answer- increased basal metabolic rate, increased warmth, weight loss, insomnia; diagnosed by decreased level of TSH Hypothyroidism - Answer- decreased BMR, excessive sleeping, weight gain; diag by ^ TSH Gigantism - Answer- only in children, ^ GFR's Action of PTH - Answer- stim conversion of vit D to active form; vit D then promotes calcium absorption in intestine rifampin - Answer- inhibits RNA poly (DNA-dep, RNA poly) alpha-amanitin - Answer- irreversibly binds to RNA poly II Describe function of RNA poly I, II, and III - Answer- I - rRNA II - mRNA III - tRNA ciprofloxacin - Answer- ib proDNA gyra