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. In x linked - in males - prevalence is...
Liver mit and liver cytosol
Less; more
In hepatocytes; B6
= q

2. What are the findings in Niemann Pick disease?
Progressive neurodegeneration (spasticity d/t UMN disease) - hepatosplenomegaly - cherry red spot on macula - foam cells
Mitochondria in liver; HmG CoA synthetase; amino acids and beta oxidation of FA
Respiratory burst - P450 - and glutathione reductase
Pyruvate dehydrogenase; ATP - NADH - acetyl CoA

3. What is the main clinical presentation of hartnup disease?
Release alk phos
only L form
Pellagra
glucagon - insulin and epinephrine

4. __________ adds N linked oligosaccharides to proteins
the RER
Which dimerizes and activates a protein phosphatase Which de phosphorylates glycogen phosphorylase
Bacterial synthesis in the intestine
Tetrahydrofolates

5. What is the rate determining enzyme in fatty acid synthesis?
In ability to reabsorb phosphate from renal tubular cells results in osteomalacia due to defective bone mineralization; no
Fructose gets phosphorylated into fructose 1- P by fructokinase and then fructose 1P gets metabolized into DHAP or glyceraldehyde by aldolase B
Citrate shuttle in the inner mitochondrial membrane transports acetyl coA into the cytoplasm; liver; liver and adipose tissue
Acetyl CoA carboxylase

6. What inhibits pyruvate dehydrogenase? What activates it?
Ret
NADH - Acetyl CoA - ATP; NAD+ - ADP and Ca2+
IMP
Glycosylases (only remove the base - cut the bond between ribose and base)

7. Homocysteine gets turned into methionine by...
Glycolysis and aerobic respiration
UV specific endonucleases for excision repair; AR; dry skin - photosensitivity - poikiloderma - susceptibility to skin cancers
Williams
homocysteine transferase

8. How is muscle activity and glycogenolysis coupled in muscle?
paternal
Calcium and calmodulin activate glycogen phosphorylase kinase
Glycine; heme
Developmental delay - gargoylism - airway obstruction (d/t short neck) - corneal clouding - CAD - hepatosplenomegaly

9. What contributes to the acidosis in alcoholism?
Thick mucus plugs lungs recurrent pulmonary infections (pseudomonas and aureus) - chronic bronchitis - bronchiectasis (which can lead to cor pulmonale!); biofilms form on resp tract
Arg
Lactic acidosis and ketoacidosis
A topoisomerase II inhibitor; because cancer cells use II more so than healthy cells

10. Name two antineoplastic drugs that work by inhibiting the mitotic spindle by MT blocking.
Vincrstine (vinca alkaloids) and paclitaxel
Self mutilation - aggression - mental retardation - gout - hyperuricemia - choreathetosis
Niacin/Nicotinic acid; NAD+ and NADH used in redox reactions - and catabolic and anabolic reactions; B6; tryptophan
Water soluble vitamin stored in liver; converted to THF by dihydrofolate reductase and is a coenzyme in 1 methyl transfers - impt for DNA synth

11. What is the precursor for both purines?
Branched chain alpha keto acid dehydrogenase; inability to break down branched chain aa
IMP
3 NADH - 1 FADH2 - 2 CO2 - 1 GTP = 12 ATP/acetyl CoA
UV specific endonucleases for excision repair; AR; dry skin - photosensitivity - poikiloderma - susceptibility to skin cancers

12. What is the deficient enzyme in Niemann Pick disease? accumulated Substrate?
Alpha ketoglutarate; no TCA cycle intermediates
2/3; LCAT (lecithin cholesterol acyltransferase)
Differentiation of cells - vision in reduced light (retinol makes up rhodopsin cells) - antioxidant
Sphingomyelinase; sphingomyelin

13. What are the symptoms involved in lactase deficiency?
Lack of proper dietary therapy during pregnancy resulting in infant's microcephaly - mental retardation - growth retardation and congenital heart defects
Osmotic diarrhea - bloating - cramps
Vit C; Vit E
Degeneration of retinal ganglion cells and axons; acute loss of central vision; mit. inheritance

14. What is the source of Vitamin B1? What is its other name? What causes a deficiency in B1?
S. aureus - Aspergillus
Enriched whole grain cereals and other things; thiamine; malnutrition (nonenriched white processed bread and rice) and alcohol second to malnutrition
When water is pulled in; polyols (sugar alcohols); cataracts - retinopathy - peripheral neuropathy all seen in chronic hyperglycemia in diabetes
Whether or not the patient is also hyperammonemia (if yes - then OTC def)

15. What are the findings in ornthinie transcarbamoylase?
This depends on if phosphofructokinase 1 is active and this depends on whether or not fructose 2.6 bisphophate is activating it or not - this can only occur if PFK 2 is on and not FBPase 2. then fructose 6 phosphate will participate in glycolysis. Ot
Citrate - Isocitrate - alpha ketoglutarate - Succinyl CoA - Succinate - Fumarate - Malate - Oxaloacetate
Convulsions - hyperirritiability - peripheral neuropathy - sideroblastic anemias; alcoholics and INH and fortified goats milk consumption
Orotic acid in blood and urine (from pyrimidine synthesis) - decreased BUN - and symptoms of hyperammonemia

16. Which RNA polymerase synthesizes tRNAs and snRPs?
III
Branched alpha ketoacid dehydrogenase
Chorea and spastic paresis
Lipoprotein lipases take FA from VLDL and chylomicrons Which are then combined with glycerol 3 P (a carb intermediate) to make triacylglycerol

17. What is the exception to degeneracy in the genetic code?
HMG CoA synthetase; HMG CoA reductase
Schwann cells - lens - retina - kidneys because they only have aldose reductase and no sorbital dehydrogenase
Tyrosine; tryptophan
Methionine is only encoded by AUG

18. What is the deficient enzyme in Von Gierkes disease? What are the findings?
Severe fasting hypoglycemia - very high levels glycogen in liver - high blood lactate - hepatomegaly
Alpha amanitin; mushroom caps
Both add phosphate; phosphorylase uses no ATP and inorganic phosphate
glycogenolysis

19. What is achondroplasia? What type of inheritance?
Presence of normal and mutated mtDNA (like mosaicism except in mit)
Cell signaling defect in FGF receptor resulting in dwarfism and short limbs with normal head and trunk; AD
AD
Because that is Where the products will be consumed; acetyl coA; TCA cycle of ketone body production

20. What does FISH stand for? What is it used for? Give an example.
Neurologic lesions and cardiomyopathies (ox phos!)
Arginine
Tyrosine
Flourescent DNA/RNA In SITU hybridization; for visualization of anomalies (like microdeletions) that are too small to be seen on karyotype; Prader - Willi syndrome

21. What metabolic reactions occur in the cytoplasm?
Pigmented iris hamartomas
Cardiomegaly - cyanosis - tachycardia - dyspnea - vomitting; 2-3 months
Cleft palate - Abnormal faces - thymic aplasia (t cell def) - Cardiac defects - hypocalcemia (secondary to hypoparathyroid); 3rd and 4th branchial pouch aberrant development
Glycolysis - fatty acid synthesis - HMP shunt - protein synthesis (RER) - steroid synthesis (SER) - glycogenolysis - glycogenesis

22. How is the nitrogen of amino acids transferred to the liver for the urea cycle? explain this process.
As alanine; amino acids donate their amino group to alpha ketoglutarate making it glutamate and the aa then becomes an alpha ketoacid (joins TCA cycle); glutamate then converts pyruvate to alanine by donating its amino group to pyruvate (with ALT); a
Glycogen phosphorylase
Via fructose 1 P by fructokinase in the liver; as glucose 1 by being GALT- ed ;)
Orotate

23. AD disease...
Glutamate
'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
= q
usually present late

24. What converts dihydrobioterin back to tetrahydrobioterin factor? What energy carrier is used? in What reactions is this cofactor used?
RER in nucleus (synthesize NTs)
Complex I - Complex II (lower energy)
7 dehydrocholesterol
Dihydropterin reductase; NADP+; phenylalanine to tyrosine and tyrosine to DOP

25. What syndrome is characterized by hyperextensible skin and joints - and bleeding? What is the most common reason? What are other clinical symptoms?
Dermatitis - glossitis - diarrhea
MT!
Ehler Danlos; type III collagen def; joint dislocation - berry aneurysm - ecchymoses - organ rupture
Citrate is positive on it - AMP and fructose 2 -6 bisphosphate is negative on it; gluconeogenesis

26. ____ soluble vitamins are more likely to result in toxicity
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
AD (trinucleotide expansion is not a mode of inheritance)
kidney
fat

27. What type of enyzmes are used in base excision repair?
adrenal medulla
Oxaloacetate gets shifted to malate d/t excess NADH
Glycosylases (only remove the base - cut the bond between ribose and base)
Decreased substrate for gluconeogenesis (pyruvate to lactate and not oxaloacetate); and pyruvate doing only lactic acidosis and not glycolysis

28. What is dysgeusia?
Mental and growth retardation; seizures - fair skin - eczema - musty body odor; neurotoxic ketones and acids stimulate vomitting - can lead to pyloric stenosis
Inability to taste
Constitutive - random insertion of gene into mouse genome; conditional - targeted through homologous recombination
Uracil; thymine

29. What disease is associated with chromosome 7?
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)
Met - arg - val - his
As alanine; amino acids donate their amino group to alpha ketoglutarate making it glutamate and the aa then becomes an alpha ketoacid (joins TCA cycle); glutamate then converts pyruvate to alanine by donating its amino group to pyruvate (with ALT); a
Williams

30. On a 100 meter sprint What is used as energy? in general What is the rule with exercise? What is used in 1000 meter run?
Stored ATP - creatine phosphate - anaerobic glycolysis; as distances increase - ATP is obtained from additional resources; above plus ox phos
Nitric Oxide - creatinine - Urea
Fructokinase; benign - fructose in the blood and urine
In ability to reabsorb phosphate from renal tubular cells results in osteomalacia due to defective bone mineralization; no

31. All the glycogen storage diseases...
Hepatic fatty change
Also have fair skin - blond hair - blue eyes - eczema
Carbomyl phoshpate synthetase I
are AR

32. From What aa does serotonin come from? What NT is serotonin a precursor for?
Disulfiram (antabuse); acetaldehyde accumulate contributing to hangover
Electron transport inhibitors - ATPase inhibitors - Uncoupling agents (increase permeability of the membrane - loss of hydrogen gradient)
Tryptophan; melatonin
Release alk phos

33. What is the first step in the respiratory burst/oxidative burst? in What disease is this deficient?
NF1
Pyruvate (through OXA); lactate - alanine - malate (and all other TCA intermediates through OXA) - glycerol - odd chain fatty acids yield propionyl coA Which can be converted to succinyl coA and enter as TCA cycle
FA coA synthetase combines coA with FA to make acyl coA
NADPH oxidase; CGD

34. With What tool are Prader Willi and Angelman diagnosed?
degradation
FISH
Pyruvate dehydrogenase; ATP - NADH - acetyl CoA
Inosine/IMP; adenosine deaminase

35. Only muscle and brain have transferase enzyme that converts ketone bodies to...
Mucus secreting goblet cells - ab secreting plasma cells - nt secreting neurons
acetyl coA
Carbomyl phosphate synthetase I
Glycerol and propionyl coA; lactate and alanine

36. What does severe deficiency of B3 lead to? What are the causes?
Myoclonus epilepsy
S - adenosyl methionine
Pellagra (dermatitis - diarrhea - dementia); INH use - B6 deficiency - Hartnup disease - malignant carcinoid syndrome - and a corn based diet (lacks trp and niacin in corn cant be absorbed)
Glycogen phosphorylase

37. What are the functions of Microtubule proteins?
Phosphorylation of glucose to yield glucose 6 phosphate; ATP; first step of glycolysis
A cytoskeletal protein - apart of flagella - cilia - mitotic spindles and transport (in neurons for example)
Amniocentesis karyotyping
Cystathionine (which then goes to cysteine) via cystathionine reductase; B6

38. What are the symptoms of williams syndrome? What is the pathogenesis?
NF2 - DiGeorge/Velocardiofacial syndromes
Folinic acid; does not require DHF
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
Distinctive elfin faces - mental retardation - hypercalcemia d/t sensitivity to vit D - well developed verbal skills and extreme friendliness - CV problems

39. What is the presentation of G6PD deficiency?
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
Hemolytic anemia with a blood smear with heinz bodies and bite cells (phagocytic removal of heinz bodies)
Mannose
Isoleucine - valine - leucine

40. All glutamate goes to _______ d ammonia is used as a buffer in urine
kidney
Lactose (glucose and galactose)
Macrocytic megaloblastic anemia - hypersegmented PMNs - subacute combined degeneration myelopathy Which results in degeneration of the dorsal and lateral columns (loss of position and vibration sense - spastic paresis and ataxia) due to abnormal myel
Tryptophan; niacin

41. What is the rate determining enzyme in de novo pyrimidine synthesis?
COP I
Carbomyl phosphate synthetase II
Cortisol; inhibits insulin action
Delayed wound healing - hypogonadism - decreased adult hair - dysgeusia - anosmia - and alcoholic cirrhosis - perioral rash

42. In What tissues can sorbitol accumulate? why?
Schwann cells - lens - retina - kidneys because they only have aldose reductase and no sorbital dehydrogenase
Amniocentesis karyotyping
Niemann pick and Tay Sachs; hepatosplenomegaly or not
Which dimerizes and activates a protein phosphatase Which de phosphorylates glycogen phosphorylase

43. What does oligomycin do?
succinyl coA (and then to OXA)
Block ATP synthase resulting in no ATP production and an increased proton gradient
Vit D levels
Trinucleotide expansion diseases

44. What does methotrexate do? What step is this enzyme involved in?
To amplify a specific desired fragment of DNA
Oral uridine administration; provides nucleosides and provides feedback inhibition
Encode enzymes for oxphos mit reactions
It inhibits conversion of DHF to THF by blocking dihyrdofolate reductase

45. What are flagella made of?
tubulin dimer
Genotyping for mutant alleles (different sizes)
MT!
Vit D levels

46. What type of disease is MERRF? What is the clinical presentation?
Aldolase B; Fructose 1 phosphate accumulates Which uses up Phosphate and the result is inhibition of gluconeogenesis without phosphate; hypoglycemia - jaundice - cirrhosis - vomitting
Dopamine beta hydroxylase; vit C
Following gastroenteritis and kwashiokor (protein deficiency)
Myoclonus epilepsy

47. What is hepatocellular steatosis?
3 hydrogen bonds; 2 hydrogen bonds
Hepatic fatty change
Pellagra
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

48. why is there decreased immunity in kwashiokor and marasmus?
No protein!
No
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)
Decrease AFP - increased BCHG - decreased estriol - increased inhibin A

49. After citrulline is produced and in the cytoplasm What happens next in the urea cycle?
Inhibits lipoic acid; lipoic acid is a cofactor for pyruvate dehydrogenase
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
glutton
Lactose in mothers milk contains galactose

50. What is the first step of collagen synthesis? 2nd step? 3rd step? 4th step? Where do all these steps occur?
Abs against type IV collagen; pulmonary and glomerular capillaries
Formation of the alpha chains out of glycine - lysine - proline in the RER to make preprocollagen; hydroxylation of the proline and lysine residues in the RER; glycosylation of the lysine residues to make procollagen Which is triple helix of alpha ch
FA coA synthetase combines coA with FA to make acyl coA
Exons

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