Test your basic knowledge |

USMLE Step 1 Biochemistry

Subjects : health-sciences, usmle-step-1

Instructions:

Answer 50 questions in 15 minutes.
If you are not ready to take this test, you can study here.
Match each statement with the correct term.
Don't refresh. All questions and answers are randomly picked and ordered every time you load a test.

This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.

1. What is carnitine deficiency and What does it result in?
Inability to transport LCFA into mitochondria results in their build up and causes weakness - hypotonia And HYPOKETOTIC HYPOGLYCEMIA
Fruits and vegetables
Homocystinuria (homocysteine damages endothelial cells); alkaptonuria (tyrosine degradation); homocystinuria
Gets converted to pyruvate via the Cori cycle in the liver

2. What converts pyruvate to Acetyl CoA ? What allosterically downregulates this enzyme?
Thinned cornea from lack of connective tissue so see underlying choroidal lens
Alpha galactosidase A; ceramide trihexoside
Pyruvate dehydrogenase; ATP - NADH - acetyl CoA
Metanephrine

3. What is phenylethanolamine N- methyl transferase located?
Niacin treatment for hyperlipidemia; facial flushing
Citrate - Isocitrate - alpha ketoglutarate - Succinyl CoA - Succinate - Fumarate - Malate - Oxaloacetate
Adrenal medulla
Increased homocysteine in the urine - mental retardation - osteoporosis - marfanoid habitus - and atherosclerosis

4. Like mRNA has a poly A tail on the 3' end - What does tRNA have on its 3' end? What happens here?
CCA and chemically modified bases Where amino acid is covalently bonded
AD (trinucleotide expansion is not a mode of inheritance)
When one allele on a gene is only expressed and the other is methylated/inactivated; during gametogenesis one of the alleles is methylated because the gamete from the other sex will provide those characteristics for the child
Reserve supply of glucose in the fasting state - liver gives to the blood and skeletal muscle uses for itself

5. Which Hurlers is milder and presents with no corneal clouding?
Hypophosphatemia rickets and Alports
Calcium and calmodulin activate glycogen phosphorylase kinase
Edwards
XR - iduronate sulfatase

6. What enzyme is used in the oxidative phase of HMP shunt? nonoxidative?
Fatty acid (acyl coA) oxidation to acetyl coA; increase in dicarboxylic acids - and decreased glucose and ketones
G6PD dehydrogenase; transketolases
glycogen
2 -4 dinitrophenol - aspirin - and thermogenin (in brown fat)

7. What enzyme is deficient in galactokinase deficiency? What are the symptoms?
Mit encephalopathy - lactic acidosis - stroke like episodes
Galactokinase; galactose appears in blood and urine - sometimes infantile cataracts may present as failure to track objects or lack of a social smile
tumor suppressor genes (p53 - Rb - BAX)
Increased acid production competes with uric acid for excretion

8. What is the rate determining enzyme in urea cycle?
Carbomyl phosphate synthetase I
Endonucleases are specific and break specific linking phosphodiester bonds - exonucleases are not sequence specific and just remove the nucleoside
Bendy bones seen in children due to decreased Vit D; craniotabes - skeletal deformities - growth retardation - rosary
Stored ATP - creatine phosphate - anaerobic glycolysis; as distances increase - ATP is obtained from additional resources; above plus ox phos

9. Daughters of Xlinked recessive diseased fathers are...
Tyrosine hydroxylase; tetrahydrobiopterin factor; NADP+
Down's Syndrome
all carriers
Less; more

10. Where is anaerobic glycolysis used often?
Because carbamaoyl phosphate is involved in both urea cycle and pyrimidine synthesis
RBCs - renal medulla - leukocytes - lens - testes - cornea
Glucagon - insulin and epinephrine
ATP

11. What is the major cause of B12 def? What is the clinical picture of this?
P53 and Rb; p53 activates BAX Which inhibits BCL2 When there is DNA damage - Rb phosphorylation allows progression into S phase
Phenylaline
Pernicious anemia; older - mentally slow european woman who is anemic and icteric with a smooth shiny tongue and has broad based shuffling gait
Which dimerizes and activates a protein phosphatase Which de phosphorylates glycogen phosphorylase

12. What is the mcc of an autosomal trisomy?
Codons may encode same amino acid since there are only ~20 aa
Adrenal medulla
Heart - SKELETON - and EYES: arachnodactyly - long limbs - cystic medial necrosis of aorta resulting in aneurysms (and eventual dissection) - floppy mitral valve (prolapse and regurg!) - subluxation of lens
Meiotic nondisjunction in mothers gametes during the first meiosis

13. The mode of inheritance for both NF disease is...
Creates nicks in DNA to prevent supercoiling; both!
Both AD
5'--> 3'; prokaryote only; for removing RNA primer and filling it with DNA
Tyrosinase

14. deamination of What pyrimidine makes what?
Cytosine to uracil
Increased nuchal translucency
Fabrys Disease and Hunters Syndrome
Differentiation of cells - vision in reduced light (retinol makes up rhodopsin cells) - antioxidant

15. What is main lab finding in Lesch Nyhan syndrome? due to What enzyme deficiency? What reaction is deficient?
Decreased would healing; microcytic anemia (d/t decreased iron [not absorbable]; macrocytic anemia (d/t Fh4 not reduced)
Heterochromatin; euchromatin
Uric acidemia; HGPRT; purine salvage
2 NADH - 2 ATP - 2 pyruvate - 2H+ - 2H20

16. In What cells does the Respiratory burst occur? Where is NADPH located in the cell? What is this reaction important for?
Neutrophils and monocytes; membrane bound; immune response by generating Reactive oxygen species
H1
Adenosine deaminase deficiency; Severe combined immunodeficiency disease
A 16C FA! the product in FA synthesis; saturated; no double bonds

17. What disease is associated with chromosome 17?
NF1
cell cycle events
Flouroquinolones
S adenosyl homocysteine; homocysteine transferase; B12 and THF; M- THF

18. What can cause a vit C deficiency?
Renal calculi of uric acid (replaces uric acid in excretion)
Smoking (FR takes up all the antioxidants); diets lacking fruit
UV nonionizing radiation causing thymidine dimers
Mental retardation - excessive laughter - seizures - ataxia - 'happy puppet'

19. What is the effect of defiiency of VIt E?
Increased acid production competes with uric acid for excretion
Hemolytic anemia (fragility of RBCs) - muscle weakness and posterior column and spinocerebellar tract demyelination (neuron damage) resulting in decreased proprioception and vibration sensation - and peripheral neuropathy - and retinal degeneration
hexokinase - glucokinase (its a glutton)
reabsorbs

20. What factors is Vit K responsible for the synthesis? and What else?
Citrate - Isocitrate - alpha ketoglutarate - Succinyl CoA - Succinate - Fumarate - Malate - Oxaloacetate
10 - 9 - 7 - 2; protein C and S
Enriched whole grain cereals and other things; thiamine; malnutrition (nonenriched white processed bread and rice) and alcohol second to malnutrition
Aminoglycosides and tetracyclines

21. What aa degradation disorder results in atherosclerosis? debiltating arthralgias? osteoporosis?
Fat soluble; either endogenous production or exogenous; D2 ergocalciferol is ingested from plants and D3 cholecalciferol is formed in sun exposed skin (and can be consumed in fortified milk)
homocysteine transferase
Homocystinuria (homocysteine damages endothelial cells); alkaptonuria (tyrosine degradation); homocystinuria
Exons

22. Phenylethanolamine N- methyl is only located in the...
Phosphoenolpyruvate; pyruvate kinase; fructose 1 - 6 BP; ATP - alanine
Disulfiram (antabuse); acetaldehyde accumulate contributing to hangover
Homocysteine; homocysteine methyltransferase with B12 and tetrahydrofolate
adrenal medulla

23. After citrulline is produced and in the cytoplasm What happens next in the urea cycle?
Alcohol dehyrogenase (alcohol to acetaldehyde); acetaldehyde dehydrogenase (acetaldehyde to acetate); NAD+; B3 (niacin)
Citrulline is combined with aspartate to make arginosuccinate Which is then split into fumarate (which leaves to enter TCA) and arginine. Arginine is then converted to Ornithine (via arginase) giving off Urea Which then goes to the kidney and ornithi
Arylsulfatase A; cerebroside sulfate
Steroid - cholesterol FA synthesis; HMP shunt

24. What is the source of Biotin?
Bacterial synthesis in the intestine
AD (trinucleotide expansion is not a mode of inheritance)
Vit K; neonates have sterile intestine and can not synthesize vit K
Phenylalanine hydroxylase; tetrahydrobiopterin factor

25. How do hepatocytes release glucose 6 P from glycogenolysis into the blood ? in What disease is this enzyme deficient?
With glucose 6 phosphatase; Von Gierkes disease
Genotyping for mutant alleles (different sizes)
allosteric regulation
CCA and chemically modified bases Where amino acid is covalently bonded

26. What is most often mutated in xeroderma pigmentosum? What is the inheritance pattern? What are the clinical symptoms?
Tay Sachs - Niemann Picks - Gauchers
Lactating mammary glands - adrenal cortex (sites of fatty acid or steroid synthesis) - RBCS (for glutathione reduction for FR injury)
UV specific endonucleases for excision repair; AR; dry skin - photosensitivity - poikiloderma - susceptibility to skin cancers
Kartaganer's aka ciliar dyskinesia; lack of dynein arm ATPase

27. What two anti - neoplastic drugs work by blocking DNA and RNA polymerase?
Promoter binds RNA Pol II and is very close (25 bases) to initiation site and is AT rich; enhancer/silencers bind TFs only - can be located close or far and regulate gene expression but not specifically initiation; transcription
Dactinomycin - doxorubicin
Phosphoenolpyruvate; pyruvate kinase; fructose 1 - 6 BP; ATP - alanine
AAUAAA; Poly A polymerase; no

28. What are required for splicing? encoded by What polymerase?
Abs against type IV collagen; pulmonary and glomerular capillaries
hexokinase (glucokinase only found in liver and beta cells of pancreas)
SnRNPs; RNA polymerase III
DNA dependent RNA polymerase

29. Where is type 1 collagen found?
Phenylaline
hexokinase (glucokinase only found in liver and beta cells of pancreas)
pleiotropic
Bone - Skin - Tendon - dentin - fascia - cornea - late wound repair

30. What are the three results that come from increased NADH in alcohol metabolism?
fatty acid degradation
A topoisomerase II inhibitor; because cancer cells use II more so than healthy cells
Dilated capillaries and veins; skin - mucous membranes - GI - resp - urinary tracts; rupture and can cause epistaxis - hemorrhage - GI bleeding
Pyruvate to lactate (results in lactic acidosis and decreased pyruvate for oxaloacetate for gluconeogenesis) - increased production of glycerol 3 phosphate from DHAP for TG synthesis; and increased betahydroxybutyrate ketoacid production from increas

31. What is Pleiotropy? What is the opposite of Pleiotropy? Give an example of each.
Arg - lys - his; positive except His has no charge at body pH
Mitochondrial inheritance
1 gene has greater than 1 phenotypic effect; locus heterogeneity (many different mutations can cause the same phenotype); PKU; albinism - deafness - Marfanoid habitus (Marfans - MEN 2B - homocystinuria)
Galactose

32. What can cause hypervitaminosis D?
Hexosaminidase A; GM2 ganglioside
Kidney and intestinal epithelium
Cell signaling defect in FGF receptor resulting in dwarfism and short limbs with normal head and trunk; AD
Iatrogenic - granulomatous disease (sarcoidosis d/t epitheloid macrophage release of calcitriol); hypercalcemia - hypercalciuria (renal calculi!) - loss of appetite - stupor

33. How do digoxin and digitoxin work? What class of drugs are they?
TPP (from B1- pyrophosphate) - FAD (B2) - NADH2 (B3) - CoA (B5 - panothenate) - Lipoic Acid
Bacteria produce lactate acid and gases from lactose and produce acidic diarrhea and bloating
Inbit Na+K+ ATPase; Cardiac glycosides
Vomiting - rice water stools - garlic breath

34. What are the functions of Microtubule proteins?
degradation
A ketone
Self mutilation - aggression - mental retardation - gout - hyperuricemia - choreathetosis
A cytoskeletal protein - apart of flagella - cilia - mitotic spindles and transport (in neurons for example)

35. What is imprinting?
Because carbamaoyl phosphate is involved in both urea cycle and pyrimidine synthesis
Alcoholism - RA - inflammatory disease - chronic diarrhea
Familial Adenomatous Polyposis (APC gene)
When one allele on a gene is only expressed and the other is methylated/inactivated; during gametogenesis one of the alleles is methylated because the gamete from the other sex will provide those characteristics for the child

36. What goes on with G0 cell cycle phase?
Cells that are stable go in and out of the G1 to G0 Which is the stable/quiescent (can go into replication but dont) type of cells; cells that stay in G0 are permanent and can not enter G1
Myotonic Dystrophy (CTG) - Huntington (CAG) Friedricks Ataxia (GAA) - Fragile (CGG)
Its When two acrocentric chromosomes combine their long arms (and short arms disappear); When the translocation is functional
activation of PFK1

37. What are the key intermediates in the TCA?
AR
Lyonization; nondisjunction in mitotic divisions during embryonic period
Citrate - Isocitrate - alpha ketoglutarate - Succinyl CoA - Succinate - Fumarate - Malate - Oxaloacetate
Heme synthesis - urea cycle - gluconeogenesis

38. What aa becomes essential with homocystinuria? phenylalaninuria?
3 hydrogen bonds; 2 hydrogen bonds
Glycosylases (only remove the base - cut the bond between ribose and base)
Cysteine; tyrosine
Mental retardation - rocker bottom feet - micrognathia (small jaw) - low set ears - clenched hands with polydactyly - congenital heart disease

39. What disease is associated with chromosome 7?
Cystic Fibrosis (CFTR gene)
Creates nicks in DNA to prevent supercoiling; both!
AD
Arginine

40. AR disease are usually...
Biotin; rate limiting step in fA synthesis - acetyl coA into malonyl coA
Kartaganer's aka ciliar dyskinesia; lack of dynein arm ATPase
Excess ATP and dATP has negative feedback inhibition on ribonucleotide reductase Which results in decreased DNA synthesis and thus decreased lymphocyte count
enzymatic

41. Which amino acids are acidic? are they negatively or positively charged at body pH?
Glucose 6 phosphate dehydrogenase
Blood group types
Asp and glu; negatively
When child gets two chromosomes from one parent; imprinting dx

42. What disease is associated with chromosome 15?

Warning: Invalid argument supplied for foreach() in /var/www/html/basicversity.com/show_quiz.php on line 183

43. What are the four irreversible enzymes of gluconeogenesis and Where in the cell are they found? Which is deficient in von gierkes disease?
G6PD dehydrogenase; transketolases
Pyruvate carboxylase (pyruvate to OXA) (mit) - PEP carboxykinase (OXA to PEP) (cyt) - Fructose 1 -6 bisphophatase (fructose 1 -6 bisphosphate to fructose 6 P) (cyt) and glucose 6 phosphatase (in ER); glucose 6 phosphatase
Immediately after replication - DNA is unmethylated and so it is a signal to be double checked; HNPCC; heterochromatin
False; GTP hydrolysis

44. Which cells have the most FA and thus are the most susceptible to FR injury?
Orotic acid in blood and urine (from pyrimidine synthesis) - decreased BUN - and symptoms of hyperammonemia
Neurons and RBCs
Dynein - retrograde - kinesin - anterograde
Chorea and spastic paresis

45. What kind of DNA damage does ionizing radiation cause? What type of repair helps with this?
Double strand breaks; nonhomologous end joining
Nitric Oxide - creatinine - Urea
Pulmonary - GI - reproductive (infertility in male due to absence of vas deferens and seminal fluid thickness)
When the amino acid is covalently binded to its corresponding tRNA; Aminoacyl tRNA synthetase; ATP; translation

46. What does methotrexate do? What step is this enzyme involved in?
Matrix; intermembrane space
It inhibits conversion of DHF to THF by blocking dihyrdofolate reductase
The products of FA oxidation (Acetyl CoA and NADH) phosphorylate pyruvate deyhdrogenase Which inactivates it
BM; laminins; most flexible; different aa composition

47. With What gene are MEN 2A and 2B associated with?
Blood group types
Ret
When the 2nd hit of the allele is What causes the disease; sporadic retinoblastoma
ATP synthase - ATP- ADP translocase - ETC

48. What carries activated Phosphate groups?
GALT
ATP
CCA and chemically modified bases Where amino acid is covalently bonded
homocysteine transferase

49. What happens to homocysteine after converting a methyl?
Becomes methionine
Positive on phosphofructokinase 1 and negative on fructose 1 -6 bisphosphatase
Branched alpha ketoacid dehydrogenase
Leucine and lysine

50. What causes an excess of B3? What are the symptoms?
Exons
Niacin treatment for hyperlipidemia; facial flushing
Galactose gets converted to galactose 1 Phosphate by galactokinase Which then gets turned into glucose 1 phosphate by Galactose 1 Uridyl Transferase (GALT) Which also produces UDP Gal Which is used for lactose production in the breast; the fate of gl
linked recessive

Sorry!:) No result found.

Can you answer 50 questions in 15 minutes?

Major Subjects
Tests & Exams AP CLEP DSST GRE SAT GMAT	Certifications CISSP go to https://www.isc2.org/ PMP ITIL RHCE MCTS More...	IT Skills Android Programming Data Modeling Objective C Programming Basic Python Programming Adobe Illustrator More...	Business Skills Advertising Techniques Business Accounting Basics Business Strategy Human Resource Management Marketing Basics More...
Soft Skills Body Language People Skills Public Speaking Persuasion Job Hunting And Resumes More...	Vocabulary GRE Vocab SAT Vocab TOEFL Essential Vocab Basic English Words For All Global Words You Should Know Business English More...	Languages AP German Vocab AP Latin Vocab SAT Subject Test: French Italian Survival Norwegian Survival More...	Engineering Audio Engineering Computer Science Engineering Aerospace Engineering Chemical Engineering Structural Engineering More...
Health Sciences Basic Nursing Skills Health Science Language Fundamentals Veterinary Technology Medical Language Cardiology Clinical Surgery More...	English Grammar Fundamentals Literary And Rhetorical Vocab Elements Of Style Vocab Introduction To English Major Complete Advanced Sentences Literature Homonyms More...	Math Algebra Formulas Basic Arithmetic: Measurements Metric Conversions Geometric Properties Important Math Facts Number Sense Vocab Business Math More...	Other Major Subjects Science Economics History Law Performing-arts Cooking Logic & Reasoning Trivia

Test your basic knowledge |

USMLE Step 1 Biochemistry

Sorry!:) No result found.

Can you answer 50 questions in 15 minutes?

Let me suggest you:

Browse all subjects

Browse all tests

Most popular tests

Major Subjects

Tests & Exams

Certifications

IT Skills

Business Skills

Soft Skills

Vocabulary

Languages

Engineering

Health Sciences

English

Math

Other Major Subjects

Browse all subjects

Browse all tests

Most popular tests