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 RNAi? and How is it used in gene expression modification?
D2 (ergocalciferol) - D3 (cholecalciferol) - D3 (cholecalciferol)
Double stranded RNA is created that is complementary to the mRNA of interest and When inserted into cells the strands separate and attach to the mRNA preventing it from being translated
Fruits and vegetables
Alanine aminotransferase (ALT) and aspartate aminotransferase (AST); alanine to pyruvate and aspartate to oxaxloacetate

2. What is the defect that causes Alport's Syndrome? What is the most common inheritance pattern? What are the three mc clinical presentations?
Type IV collagen defect; X linked recessive; hereditary glomerulonephritis - deafness - ocular disturbances
SAM
Lysine and arginine; basic
Decreased substrate for gluconeogenesis (pyruvate to lactate and not oxaloacetate); and pyruvate doing only lactic acidosis and not glycolysis

3. What is the other name of Vitamine B2? In What foods can it be found?
glycogen
Riboflavin; dairy and meat
Fe2+; Fe3+
Respiratory - seminal fluid - pancreatic - gallbladder; very thick without NaCl to pull water

4. What is the treatment for cystinuria?
CCA and chemically modified bases Where amino acid is covalently bonded
Acetazolamide to alkalinize the urine
CPSII
Endonucleases - exonucleases - DNA polymerase - DNA ligase

5. There are 2 GTP per...
Fabrys Disease and Hunters Syndrome
tubulin dimer
Phosphorylation of glucose
Indirect inhibtion of the Na+/Ca+2 exchange resulting in increased intracellular calcium Which increases cardiac contractility

6. Which cell types have a high level of RER?
Gauchers; hepatosplenomegaly - aseptic necrosis of the femur - bone crises - Gauchers cells - crumpled tissue paper looking (fibrillar appearing macrophages in liver - spleen - b.m.)
Arginine
LDL; LDL oxidize atherosclerosis
Mucus secreting goblet cells - ab secreting plasma cells - nt secreting neurons

7. What does adipose tissue contribute for hepatic gluconeogenesis during starvation? muscle?
Ret
Water soluble vitamin stored in liver; converted to THF by dihydrofolate reductase and is a coenzyme in 1 methyl transfers - impt for DNA synth
Dihydrofolate reductase; vitamin B12; homocysteine
Glycerol and propionyl coA; lactate and alanine

8. name three glucogenic AA and how they enter gluconeogenesis. through What cycle do they enter gluconeogenesis?
AST (mit damage) - and GGT (d/t SER hyperplasia d/t induction of p450 generation)
Alanine (through pyruvate) - aspartate (through OXA) - glutamate (alpha ketoglutarase); TCA
Fructose gets phosphorylated into fructose 1- P by fructokinase and then fructose 1P gets metabolized into DHAP or glyceraldehyde by aldolase B
Cystathionine (which then goes to cysteine) via cystathionine reductase; B6

9. What generally results after Vitamin B1 deficiency? T/F treat b1 def - with glucose.
low Vmax
NADPH- reductive biosynthesis!
Dihydropterin reductase; NADP+; phenylalanine to tyrosine and tyrosine to DOP
ATP depletion and highly aerobic tissues (heart and brain) are affected first; false - glucose infusion worsens

10. From What aa does GABA come from? with What enzyme? and What vit cofactor? What does GABA stand for?
Glutamate; glutamate decarboxylase; B6; gamma aminobutyrate
Arg and his
No protein!
Flouroquinolones

11. What is the presentation for cystinuria?
Bone - Skin - Tendon - dentin - fascia - cornea - late wound repair
25 OH D3; 1 -25 (OH)2 D3 (Calcitriol)
Cystine kidney stones (cystine staghorn calculi)
Myotonic Dystrophy (CTG) - Huntington (CAG) Friedricks Ataxia (GAA) - Fragile (CGG)

12. What is the signal for adenylation? What enzyme does? does it require a template?
HnRNA; mRNA
AAUAAA; Poly A polymerase; no
Citrate - Isocitrate - alpha ketoglutarate - Succinyl CoA - Succinate - Fumarate - Malate - Oxaloacetate
osteosarcomas (Rb mutation is in all cells)

13. What is the metabolism of galactose like?
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
When the 2nd hit of the allele is What causes the disease; sporadic retinoblastoma
The lack of lysosomal proteins (are secreted - default from RER!) results in macromolecules accumulating in lysosomes - inclusions cause pathology
Cu; hydroxylation

14. What is cystinuria due to?
Hereditary defect of renal tubular amino acid transporter for cysteine - ornithine - lysine and arginine in the PCT of kidnyes
Increased NADH causes lactate production and pyruvate dehydrogenase def causes increased lactate (d/t thiamine def that often occurs with alcoholics)
Developmental delay - gargoylism - airway obstruction (d/t short neck) - corneal clouding - CAD - hepatosplenomegaly
Some viruses

15. What is alternative splicing? in What disease state does alt splicing occur unintentionally d/t early stop codons?
When different combination of exons get combined together; in Beta thallasemia
Pyridoxine; converted to pyridoxal phsophate used in transamination reaction - decarboxylations - heme synthesis - niacin synthesis from trp - glycogen phosphorylase - cystathionine synthesis - NT synthesis
Microcephaly - mental retardation - high pitched mewing/crying - epicanthal folds - cardiac abnormalities; microdeletion on short arm of chrom 5
Down's Syndrome

16. How do you treat fructose intolerance?
Cu; hydroxylation
Each codon specifies only one amino acid
Converts it to citrulline
Decrease intake of fructose and sucrose (fructose and glucose)

17. How is CF diagnosed?
Arginine
Increased concentration of Cl ions in sweat test
Downs
Imprinting Dx's: prader Willi and Angelmann

18. why does branching occur in glycogenesis?
Oxygen!
Branching increases the rate of synthesis and breakdown of glycogen by having more sites to add on to and break off
In the reproductive tract and in the resp tract; infertility - bronchiectasis and recurrent sinusitis - associated with situs inversus
To increase serum Ca and phosphate for bone deposition

19. deamination of What pyrimidine makes what?
Cytosine to uracil
Ehler Danlos; type III collagen def; joint dislocation - berry aneurysm - ecchymoses - organ rupture
Phenylalanine hydroxylase or tetrahydrobiopterin factor
Vincrstine (vinca alkaloids) and paclitaxel

20. How are fa oxidation and gluconeogenesis linked - ie What compound makes sure that they occur together and that glycolysis doesnt occur?
Acetyl coA and NADH inhibit pyruvate dehyrogenase
Its the ribose; its made from PRPP synthetase using ribose 5 P from the HMP shunt
RER in nucleus (synthesize NTs)
DNA dependent RNA polymerase

21. All glutamate goes to _______ d ammonia is used as a buffer in urine
Marfans - homocystinuria - MEN 2B
paternal
jaundice
kidney

22. What is the rate determining enzyme in de novo purine synthesis?
Uses HMG coA reductase
Von gierkes
Glutamine PRPP amidotransferase
Autosomal Dominant; NF1 and mit. diseases (variable expression) - ?

23. In What syndrome is HGPRT deficient? What is the inheritance pattern?
Gets converted to pyruvate via the Cori cycle in the liver
Hypophosphatemia rickets and Alports
Vit C; Vit E
Lesch Nyhan syndrome; X linked recessive

24. What are the GI clinical symptoms of CF?
Mucus secreting goblet cells - ab secreting plasma cells - nt secreting neurons
Alpha ketoacids in the blood; alpha keto acids in the urine/poo smells of maple syrup/burnt sugar
Cortisol; inhibits insulin action
Chronic pancreatitis leads to type 1 diabetes - pancreatic insufficiency leads to ADEK deficiencies - malabsorption and steatorrhea - blocked gallbladder ducts leads to secondary biliary cirrhosis

25. What does glycogen phosphorylase in glycogenolysis create?
Limit dextrans
Indirect inhibtion of the Na+/Ca+2 exchange resulting in increased intracellular calcium Which increases cardiac contractility
osteosarcomas (Rb mutation is in all cells)
Inability to transport LCFA into mitochondria results in their build up and causes weakness - hypotonia And HYPOKETOTIC HYPOGLYCEMIA

26. What regulates Fructose 1 -6 bisphosphatase? What reaction is it found in?
Glutamine - aspartate - glycine; aspartate
Because carbamaoyl phosphate is involved in both urea cycle and pyrimidine synthesis
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
Citrate is positive on it - AMP and fructose 2 -6 bisphosphate is negative on it; gluconeogenesis

27. What is the precursor in the skin that the sun turns to D3?
adrenal medulla
Inability to taste
Renal calculi of uric acid (replaces uric acid in excretion)
7 dehydrocholesterol

28. What is an ELISA? What are the two ways to perform it? What is the sensitive and specificity? give a relative clinical example.
Tryptophan; B6
Griseofulvin
Testing for antigen - antibody reactivity; can either add an antibody to a persons blood sample to see if there is binding or add an antigen to a persons blood sample to see if there immune system recognizes it; close to 100% for both; HIV eliza - an
Pyridoxine; converted to pyridoxal phsophate used in transamination reaction - decarboxylations - heme synthesis - niacin synthesis from trp - glycogen phosphorylase - cystathionine synthesis - NT synthesis

29. Which cells are rich in SER?
GALT
When there is glucagon; protein kinase A activation and thus phosphorylation of the complex resulting in the activation of fructose 2 -6 BPase and no PFK2
Downs
Adrenal cells (steroid synthesis) - hepatocytes (p450 detox)

30. What are the two most common aminotransferase and What amino acids do they turn to What glycolytic intermediates?
hexokinase (glucokinase only found in liver and beta cells of pancreas)
both liver and muscle (unlike glucagon)
Aldolase B
Alanine aminotransferase (ALT) and aspartate aminotransferase (AST); alanine to pyruvate and aspartate to oxaxloacetate

31. Breast milk has a little of...
All clathrin
Vit D and K
Oxaloacetate depleted for gluconeogenesis; excess NADH shunts oxaloactetate towards malate
It inhibits conversion of DHF to THF by blocking dihyrdofolate reductase

32. What is the treatment for phenylketonuria?
So that excess glucose can be stored (phosphorylated glucose cant leave) in the liver and saved as a buffer
Decreased phenylalanine - increase tyrosine
Oral uridine administration; provides nucleosides and provides feedback inhibition
G6PD dehydrogenase; transketolases

33. Which anticancer drugs act on MT? how are they different?
Vincristine - vinblastine - and paclitaxel; the vinca alkaloids block formation of the spindle and paclitaxel prevents breakdown of the mT spindle
Increased blood levels of ammonia - decreased BUN
aldose reductase
Very Poor Carb Metabolism (Von Gierke - Type 1 - Pompes - Type II - Cori's - Type III - McArdles disease - Type IV)

34. What is the deficient enzyme in Von Gierkes disease? What are the findings?
Lactic acidosis and ketoacidosis
Progressive neurodegeneration (spasticity d/t UMN disease) - NO hepatosplenomegaly - cherry red spot on macula - lysosomes with onion skin - muscle weakness
is asymmetric
Severe fasting hypoglycemia - very high levels glycogen in liver - high blood lactate - hepatomegaly

35. What are the common symptoms of B vitamin deficiencies?
Lime and CaCO3 to displace the niacin
Dermatitis - glossitis - diarrhea
GALT
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)

36. 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
Mental retardation - flat faces - simean crease - epicanthal folds - ASD - duodenal atresia causing Hirshsprungs disease - redundant skin at the nape of neck - slanted palpebral fissures - hypotonia
Microcephaly - mental retardation - high pitched mewing/crying - epicanthal folds - cardiac abnormalities; microdeletion on short arm of chrom 5
Neutrophils and monocytes; membrane bound; immune response by generating Reactive oxygen species

37. What is the rate determining enzyme in steroid synthesis? cholesterol synthesis?
HMG CoA synthetase; HMG CoA reductase
A 16C FA! the product in FA synthesis; saturated; no double bonds
N linked oligosaccharides
Because that is Where the products will be consumed; acetyl coA; TCA cycle of ketone body production

38. Which amino acids are basic? are they negatively or positively charged at body pH?
Lack of proper dietary therapy during pregnancy resulting in infant's microcephaly - mental retardation - growth retardation and congenital heart defects
Aldose reductase in the lens converts built up galactose to galactitol Which is osmotically active
TCA cycle - FA oxidation - acetyl coA production; ox phos
Arg - lys - his; positive except His has no charge at body pH

39. What carries CO2 as energy?
COP I
SnRNPs; RNA polymerase III
Microcephaly - mental retardation - high pitched mewing/crying - epicanthal folds - cardiac abnormalities; microdeletion on short arm of chrom 5
Biotin

40. How is entry into cell cycle phases regulated?
low Vmax
By cyclin CDK complexes
Blood group types
UV nonionizing radiation causing thymidine dimers

41. Other than anabolic processes What else is NADPH used for?
Vit D levels
S. aureus - Aspergillus
Respiratory burst - P450 - and glutathione reductase
Peripheral neuropathies of hands/feet; angiokeratomas between umbilicus and knees; cardiovascular/renal disease

42. What are the three main cytoskeletal elements?
FA coA synthetase combines coA with FA to make acyl coA
Limit dextrans
Chronic pancreatitis leads to type 1 diabetes - pancreatic insufficiency leads to ADEK deficiencies - malabsorption and steatorrhea - blocked gallbladder ducts leads to secondary biliary cirrhosis
Actin/myosin - MT - intermediate filaments

43. What is the precursor for both purines?
IMP
Convulsions - hyperirritiability - peripheral neuropathy - sideroblastic anemias; alcoholics and INH and fortified goats milk consumption
NADPH oxidase; CGD
golgi apparatus

44. How does glycerol from triacylglycerols in adipose tissue used for gluconeogenesis?
Adrenal medulla
Gets converted to glycerol 3 P Which is then converted to DHAP Which then can enter glycolyis
False; GTP hydrolysis
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

45. What aa becomes essential with homocystinuria? phenylalaninuria?
AD; disorder of blood vessels that results in telangietasias - skin discolorations - and AVMs (arteriovenous malformations)
NADPH oxidase; CGD
Cysteine; tyrosine
Lactic acidosis and ketoacidosis

46. Kwashiokor patients are not...
calorie deficient
Vit C; Vit E
'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
In the charging reaction! for this reason aminoacyl tRNA synthetase double checks

47. What is the mode of inheritance of phenyketonuria?
AR
liver and muscle
Carbomyl phosphate synthetase I
Glucagon - insulin and epinephrine

48. Which intermediate is involved in both pyrimidine synthesis and the urea cycle?
Robertsonian translocations
Alcohol dehydrogenase; cytosol; mitochondria; NAD+
Carbamoyl phosphate
Succinyl coA

49. What is the impetus for ketoacidosis in starvation? alcoholism?
Beckers is less severe (instead of deletion is either defect or deficiency) with later presentation
XR - iduronate sulfatase
Oxaloacetate depleted for gluconeogenesis; excess NADH shunts oxaloactetate towards malate
AR

50. What aa becomes essential with phenylketonuria?
Both add phosphate; phosphorylase uses no ATP and inorganic phosphate
Tyrosine
Robertsonian translocations
Testing for antigen - antibody reactivity; can either add an antibody to a persons blood sample to see if there is binding or add an antigen to a persons blood sample to see if there immune system recognizes it; close to 100% for both; HIV eliza - an

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