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 retinoic acid used for in treatments?
Stored ATP - creatine phosphate - anaerobic glycolysis; as distances increase - ATP is obtained from additional resources; above plus ox phos
Carbomyl phosphate synthetase I turns N acetyl glutamate into carbomyl phosphate and then ornithine transcarbomyalse turns carbomyl phosphate into citrulline (using ornithine)
Inability to taste
Wrinkles - acne and psoriasis topically - promyelocytic anemia - measles

2. What is the purpose of the PCR?
To amplify a specific desired fragment of DNA
Nacetyl cysteine; breaks disulfide bridges of mucus plugs
Vit D and K
They increase the permeability of the inner mit membrane resulting in a loss of gradient and loss of ATP production BUT electron transport continues! heat is generated instead

3. By What products are gluconeogenesis and glycolysis linked so that they are not both occurirng at the same time?
Vincristine - vinblastine - and paclitaxel; the vinca alkaloids block formation of the spindle and paclitaxel prevents breakdown of the mT spindle
ATP is an allosteric inhibitor on both phosphofructokinase and pyruvate kinase and pyruvate hydrogenase; and fructose 2 -6 BP Which is an allosteric enhancer on phosphofructokinase is an allosteric downregulator on fructose 1 -6 bisphophatase
Make it stiffer/more tensile; continues as we get older so gets less and less elastic
Bilateral acoustic schwannomas - juvenile cataracts

4. From What aa does serotonin come from? What NT is serotonin a precursor for?
Tryptophan; melatonin
Prolonged Ab use
Vit C
Aminoglycosides and tetracyclines

5. Which form of iron is most absorbable? What form is non heme ingested iron in (vegetables for ex)?
Lysine and leucine
Fe2+; Fe3+
Glucose 6 phosphate dehydrogenase
Phenylalanine

6. What does guanine have on it?
Isocitrate dehydrogenase
A ketone
Excess ATP and dATP has negative feedback inhibition on ribonucleotide reductase Which results in decreased DNA synthesis and thus decreased lymphocyte count
Nacetyl cysteine; breaks disulfide bridges of mucus plugs

7. The mode of inheritance for both NF disease is...
Both AD
Niemann pick and Tay Sachs; hepatosplenomegaly or not
Inosine/IMP; adenosine deaminase
Osmotic diarrhea - bloating - cramps

8. Where are receptors for Vit D? (think How does it increase serum Ca and Phosphate)
Intestine - renal - bone
AR; trinucleotide deletion results in loss of a Phe aa on CFTR gene on chrom 7- the result is a mutated CFTR channel that gets degraded in the ER before reaching the surface; the purpose of CFTR is to increase Cl secretion in luminal secretions and r
Malabsorption problems (CF and sprue) and mineral oil intake
No; increased mutation rate!

9. What carries CO2 as energy?
Dihydropterin reductase; NADP+; phenylalanine to tyrosine and tyrosine to DOP
Biotin
Alpha ketoacids in the blood; alpha keto acids in the urine/poo smells of maple syrup/burnt sugar
Damaged 'ubiquinated' cytokeratin intermediate filaments build up in hepatocytes - damaged neurofilaments in idiopathic parkinsons disease build up to form Lewy bodies - Neurofibrillary tangles are build up of neurofilaments in alzheimers

10. The plasma membrane...
Disulfiram (antabuse); acetaldehyde accumulate contributing to hangover
Liver and skeletal muscle
is asymmetric
AD: yes! most common presentation; very rare (700 mg/dl cholesterol level!)

11. What is the pathogenesis of fragile x syndrome?
Gauchers; hepatosplenomegaly - aseptic necrosis of the femur - bone crises - Gauchers cells - crumpled tissue paper looking (fibrillar appearing macrophages in liver - spleen - b.m.)
A trinucleotide repeat disorder results in faulty methylation and thus expression of the FMR1 gene on the X chromosome (x linked recessive mode of inheritance)
normal lactate levels
Dynein - retrograde - kinesin - anterograde

12. What are the GI clinical symptoms of CF?
Milder form of type 1 with normal blood lactate levels; debranching enzyme (alpha -1 -6 glucosidase)
Chronic pancreatitis leads to type 1 diabetes - pancreatic insufficiency leads to ADEK deficiencies - malabsorption and steatorrhea - blocked gallbladder ducts leads to secondary biliary cirrhosis
Incoming Aminoacyl tRNA; site Where peptidyltransferase bond is made between growing peptide aa's; the holds the empty tRNA as it exits; the initiator mRNA (met or f - met) starts off in E site rather than A site
low Vmax

13. What is methotrexate?
No protein!
Fructose bisphosphatase 2 and Phosphofructokinase 2; phosphorylation by protein kinase A; inuslin/glucagon ratio
Chronic pancreatitis leads to type 1 diabetes - pancreatic insufficiency leads to ADEK deficiencies - malabsorption and steatorrhea - blocked gallbladder ducts leads to secondary biliary cirrhosis
A folic acid analogue

14. why does branching occur in glycogenesis?
Branching increases the rate of synthesis and breakdown of glycogen by having more sites to add on to and break off
As BUN (blood urea nitrogen)
Vit D and K
Galactose

15. What contributes to the acidosis in alcoholism?
Dopamine beta hydroxylase; vit C
B hydroxybutyrate - acetone - acetoacetate; beta hydroxybutyrate; beta hydroxybutyrate
Lactic acidosis and ketoacidosis
Abnormal glycogen metabolism results in accumulation of glycogen in cells

16. What disease is associated with chromosome 3?
Chronic pancreatitis leads to type 1 diabetes - pancreatic insufficiency leads to ADEK deficiencies - malabsorption and steatorrhea - blocked gallbladder ducts leads to secondary biliary cirrhosis
Robertsonian translocations
hexokinase (glucokinase only found in liver and beta cells of pancreas)
VHL (Von Hippa Lindau)

17. What is the main source of FA? Where else can they be released from?
Schilling test
Make it stiffer/more tensile; continues as we get older so gets less and less elastic
Synthesis in liver and then hydrolysis of chylomicrons and VLDLs by capillary lipoprotein lipase in peripheral tissue; adipose tissue by lipases
Silent - misssense - nonsense

18. How do you detect the different reasons that cause cobalamin def?
Schilling test
Positive on phosphofructokinase 1 and negative on fructose 1 -6 bisphosphatase
Progressive neurodegeneration (spasticity d/t UMN disease) - NO hepatosplenomegaly - cherry red spot on macula - lysosomes with onion skin - muscle weakness
Thinned cornea from lack of connective tissue so see underlying choroidal lens

19. What is uniparental disomy? give an example of a disease it can cause.
Conversion to UDP glucose via UDP glucose pyrophosphorylase; glycogen synthase (rate limiting step )
When child gets two chromosomes from one parent; imprinting dx
Actin/myosin - MT - intermediate filaments
fatty acid degradation

20. name the water soluble vitamins.
2/3; LCAT (lecithin cholesterol acyltransferase)
osteosarcomas (Rb mutation is in all cells)
Vitamin B1 (thiamine) - Vitamin B2 (riboflacin) - Vitamin B3 (niacin) - Vitamin B5 (pantothenate) - Vitamin B6 (pyridoxine) - Vitamin B7 (Biotin) - Vitamin B12 (cobalamin) - folate - Vit. C
When the disease manifestation depends on from who the gene deletion was inherited from d/t methylation that occurs; Prader Willi and AngelMann

21. Citrate shuttle; carnitine shuttle takes acyl coA into the mit for...
fatty acid degradation
glutton
By activating adenylyl cylase Which increases cAMP Which increases levels of protein kinase A Which activates glycogen phosphorylase kinase; epinephrine
Leucine and lysine

22. What are the findings in AR Hurlers?
Ceramide trihexoside
RBCs - renal medulla - leukocytes - lens - testes - cornea
Developmental delay - gargoylism - airway obstruction (d/t short neck) - corneal clouding - CAD - hepatosplenomegaly
Chloramphenicol

23. What is lebers hereditary optic neuropathy? What is the main clinical symptom? and What is its mode of inheritance?
MT!
Degeneration of retinal ganglion cells and axons; acute loss of central vision; mit. inheritance
Galactocerebrosidase; Galactocerebroside
Cells that stay in G0 and cannot replicate - instead they regenerate from stem cells; neurons - skeletal and cardiac muscles - and RBCs

24. What is a microarray and What is it used for?
A piece of glass or silicon chip with thousands of grids with different nucleic acid sequences and DNA or RNA probes are hybridized to the chip and a scanner detects the complementary binding; used to study a persons genome and to detect snps (single
Cafe au lait spots - optic pathway gliomas - lisch nodules - scoliosis - neural tumors
kidney
ATP and biotin

25. How is urea measured
Whether or not the patient is also hyperammonemia (if yes - then OTC def)
Glutamate and aspartate; CO2 provides an ketone
Glycogen synthase
As BUN (blood urea nitrogen)

26. With What type of inheritance is variable expression and incomplete penetrance associated with? Give an example of each.
Histidine; B6
Autosomal Dominant; NF1 and mit. diseases (variable expression) - ?
Collagen; fibroblasts; 4; ECM
Ehler Danlos; type III collagen def; joint dislocation - berry aneurysm - ecchymoses - organ rupture

27. In What syndrome is HGPRT deficient? What is the inheritance pattern?
Lesch Nyhan syndrome; X linked recessive
Neurons and RBCs
Inosine/IMP; adenosine deaminase
NADH - NADPH - FADH2

28. What is the treatment for cystinuria?
Self mutilation - aggression - mental retardation - gout - hyperuricemia - choreathetosis
HMG CoA reductase; converts HMG CoA to mevalonate
The active form of Vit D (1 -25 (OH)2 D3)
Acetazolamide to alkalinize the urine

29. How is Vit K activated? What drug blocks this? What is the source of Vit K?
By epoxide reductase in the liver; coumadin; intestinal flora and leafy vegetables
Homocysteine methyltransferase - cystathionine reductase - decreased affinity of cystathionine reductase for pyridoxal phosphate; AR
Because that is Where the products will be consumed; acetyl coA; TCA cycle of ketone body production
Collagen; fibroblasts; 4; ECM

30. Other than to glycolysis - Where does glucose 6 phosphate get used for? ie What other activated carriers transmit its energy?
Dilated capillaries and veins; skin - mucous membranes - GI - resp - urinary tracts; rupture and can cause epistaxis - hemorrhage - GI bleeding
HMP shunt (to NADPH) and glycogenolysis (as glucose 1 phosphate)
FISH
Enriched whole grain cereals and other things; thiamine; malnutrition (nonenriched white processed bread and rice) and alcohol second to malnutrition

31. After day 3 of starvation - What is the main source of energy?
Alkaptonuria; ochronosis
'9+2' 9 pairs of microtubules connected by an axonemal dynein ATPase in a cylinder with 20 MTs in the center; the connecting ATPase allows bending and differential sliding
Adipose tissue for brain and heart (ketone bodies) and then go to vital protein degradation (organ failure)
degradation

32. What are the findings in Niemann Pick disease?
Amniocentesis karyotyping
Mental retardation - excessive laughter - seizures - ataxia - 'happy puppet'
Progressive neurodegeneration (spasticity d/t UMN disease) - hepatosplenomegaly - cherry red spot on macula - foam cells
CCA and chemically modified bases Where amino acid is covalently bonded

33. Is PRPP added later or first in pyrimidine synthesis?
Self mutilation - aggression - mental retardation - gout - hyperuricemia - choreathetosis
Later
IMP
Conversion to UDP glucose via UDP glucose pyrophosphorylase; glycogen synthase (rate limiting step )

34. What cofactor is required of preprocollagen hydroxylation?
Mebendazole and thiabendazole
Vit C
(cofactor for 100+ enzymes!) needed for zinc fingers transcription motif - collagen synthesis - alcohol metabolism
Arginine

35. What aa is most accumulated in hartnup disease? What vitamin becomes deficient?
long saturated fatty acids
Cobalamin; cofactor for homocysteine methyltransferase (transfers SAM to THF to give to dUMP) and for methylmalonyl coA mutaseto make succinyl coA
Tryptophan; niacin
Fructose 1 -6 bisphosphatase

36. What systems are affected by CF?
Pulmonary - GI - reproductive (infertility in male due to absence of vas deferens and seminal fluid thickness)
Structural (constitutively active)
Hepatic glycogenolysis (mostly) - also hepatic gluconeogenesis - adipose release of FFA (minor)
By giving high amounts of pyridoxal phosphate in the diet

37. What is type II collagen found?
Cartilage (including hyaline) - vitreous body - nucleus pulposus
Convulsions - hyperirritiability - peripheral neuropathy - sideroblastic anemias; alcoholics and INH and fortified goats milk consumption
Hepatic fatty change
Isoleucine - valine - leucine

38. What is the rate limiting step in glycolysis? What does it do? who activates it? inhibits it?
Do an RT PCR (reverse transcriptase)- RT the RNA first - then PCR the DNA
Homogentistic acid oxidase
Phosphofructokinase 1; fructose 1 phosphate to fructose 1 -6 bisphosphate; enhancers: AMP - fructose 2 -6 Bisphosphate; downregulators: citrate - ATP
Glutamine PRPP amidotransferase

39. What is one steroid that increases gluconeogenesis? What else does cortisol do that yields hyperglycemia?
3 NADH - 1 FADH2 - 2 CO2 - 1 GTP = 12 ATP/acetyl CoA
Cortisol; inhibits insulin action
Dermatitis - glossitis - diarrhea
Methionine; f Met (formyl methyl methionine)

40. At What point is the amino acid correspondence to the mRNA code finalized?
Glycine; proline and lysine
In the charging reaction! for this reason aminoacyl tRNA synthetase double checks
Cu; hydroxylation
2 NADH - 2 ATP - 2 pyruvate - 2H+ - 2H20

41. How many RNA polymerases do prokaryotes have? What drug blocks prokaryotic RNA polymerase only? What is it used for?
Glucokinase
1) Dry beriberi: peripheral neuropathy demyelination (symmetricul muscle wasting) 2) Wernicke: ataxia - confusion - nystagmus - mammilary body and medial dorsal nuc of thalamus hemorrhage 3) Korsakoff: anterograde and retrograde amnesia - demyelinati
1 for all three classes of RNA; Rifampin; TB
DOPA

42. Which anticancer drugs act on MT? how are they different?
AD
acetyl coA
Isoleucine - valine - leucine
Vincristine - vinblastine - and paclitaxel; the vinca alkaloids block formation of the spindle and paclitaxel prevents breakdown of the mT spindle

43. What are the functions of Microtubule proteins?
A cytoskeletal protein - apart of flagella - cilia - mitotic spindles and transport (in neurons for example)
degradation
kidney
Acetyl CoA carboxylase

44. What are the ketogenic amino acids?
Cu; hydroxylation
Leucine and lysine
Neutrophils and monocytes; membrane bound; immune response by generating Reactive oxygen species
show disease

45. other than succinate dehydrogenase What other enzymes are found in the inner mit membrane?
ATP synthase - ATP- ADP translocase - ETC
Fructokinase; benign - fructose in the blood and urine
2 -4 dinitrophenol - aspirin - and thermogenin (in brown fat)
Collections of abnormal mit collecting under sarcolemmal membranes and results in distortion of myofibrils

46. How do you treat orotic aciduria? How does this work?
Oral uridine administration; provides nucleosides and provides feedback inhibition
SAM
Genotyping for mutant alleles (different sizes)
Shiga toxin and ricin (protein in castor beans)

47. What is the source of ATP after a meal?
Glycolysis and aerobic respiration
Increased G3P for TG synthesis - increased acetyl CoA (Fatty acid synthesis for TG synthesis) - and decreased oxidation of FA in the mitochondria due to alcohols toxicity on the mit
Catalyze gamma carboxylation of glutamic acid residues on coag factors so they can bind to Ca complex
Genotyping for mutant alleles (different sizes)

48. From What aa does porphyrin come from? What is porphyrin the precursor of?
Collections of abnormal mit collecting under sarcolemmal membranes and results in distortion of myofibrils
Preprocollagen - procollagen - tropocollagen - collagen
Glycine; heme
Urea cycle enzyme deficiency (mc: ornithine transcarbamoylase); liver disease - alcoholic cirrhosis and reye's

49. What is the order of types of glycogen storage disease?

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

50. What type of disease is MERRF? What is the clinical presentation?
Myoclonus epilepsy
Metaphase (all lined up); blood - bone marrow - amniotic fluid - placental tissue; used to diagnose chromosomal abnormalities (deletions - trisomies - sex chromosomal disorders)
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
Following gastroenteritis and kwashiokor (protein deficiency)

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