High Yield Biochem Usmle Step 1

Front 1

inhibits ribonucleotide reducase, causing build up of UDP

Back 1

hydroxyurea

Front 2

blocks de novo purine synthesis

Back 2

6MP

Front 3

inhibits thymidylate synthase, causing decreased dTMP

Back 3

5FU

Front 4

inhibits dihydrofolate reductase, causing decreased dTMP

Back 4

methotrexate

Front 5

inhibits bacterial dihydrofolate reductase, causing decreased dTMP

Back 5

trimethoprim

Front 6

increased orotic acid in urine, and megaloblastic anemia that doesn't get better with b12 or folic acid.

Back 6

orotic aciduria, due to defect in orotic acid phosphoribsyltransferase, or orotidine 5'-phosphate decarboxylase -- distinguish from OTC deficiency by checking ammonia levels (OTC deficiency will have hyperammonia)

Front 7

defective purine salvage pathway, leading to excess uric acid and de-novo purine synthesis. patient will have mental retardation, self mutilation, gout, choreoathetosis, and hyperuricimia

Back 7

lesch-nyhan syndrome - x linked recessive disorder due to lack of HGPRT

Front 8

diff between DNA pol 1, and DNA pol 3

Back 8

3 - elongates leading strand of prokaryotes, has 3'-5' exonuclease activity.
1 - degredation of RNA primer with 5'-3' exonuclease activity, and fills in gaps on lagging strand.

Front 9

how are thymidine dimers caused by UV light repaired? what disease is it defective in?

Back 9

repaired by nucleotide excision repair by endonucleases. mutated in xeroderma pigmentosum

Front 10

how are spontaneous/toxic demamination repaired?

Back 10

base excision repair

Front 11

what is the DNA repair defect in HNPCC?

Back 11

mismatch repair

Front 12

what is the defect in ataxia-talangiectasia?

Back 12

nonhomologous end joining, ATP binding cassete

Front 13

where does RNA pol bind? (promotor/enhancer/etc)

Back 13

promotor - must be upstream of the gene

Front 14

where do transcription factors bind?

Back 14

promotor OR enhancer. enhancer can be upstream or downstream.

Front 15

which type of RNA pol does alpha amantin inhibit (toxin found in death cap mushrooms)

Back 15

RNA pol 2 - which makes mRNA

Front 16

what end is the cap on, what end is the polyA tail on?

Back 16

cap is on 5', tail is on 3'

Front 17

in the lac operon, what does glucose decrease? leading to what downstream effect? what does lactose bind to? what is the main protein product of the lac operon?

Back 17

glucose inhibits cAMP, which is needed to activate CAP which binds to the CAP binding site, and HELPS RNA pol bind to promotor. Lactose binds to the repressor, which otherwise would have bound to the promotor to bind RNA pol, and to the operator. Main product is B-galactosidase, which converts lactose into glucose and galactose.

Front 18

what antibiotic prevents attachment of aminoacyl-tRNA to the 30s protein?

Back 18

tetracycline

Front 19

what prevents formation of the initiation complex and causes misreading of the mRNA on the 30s protein?

Back 19

aminoglycosides

Front 20

what prevents the 50s peptidyltransferase from acting?

Back 20

chloramphenicol

Front 21

what two antibiotics prevent peptide bond formation?

Back 21

clindamycin and chloramphenicol

Front 22

what are the permanent cells that always remain in G0?

Back 22

neurons, RBCs, cardiac myocytes, and skeletal muscle

Front 23

what can RER add to proteins?

Back 23

N-linked oligosaccharides

Front 24

To what protein does the gogli add O-oligosaccharides on? on what protein does it MODIFY n-oligosaccharides?

Back 24

Adds O-oligo to serine and threonine, and modifies the N-oligo on asparagine.

Front 25

What disease do you have inherited lysosomal storage disorder characterized by failure of addition of mannose-6-phosphate to proteins targeted for lysosomes?

Back 25

I-cell disease - patient will have coarse facial features, clouded corneas, and restricted joint movements.

Front 26

what is the difference between dynein and kinesin?

Back 26

both are microtubule related, dynein carries things retrograde to microtubule, so plus end to minus end (so towards the nucleus). kinesin does it anterograde, from the minus end to the plus end (so away from nucleus).

Front 27

what defect causes dynein arm problems, leading to situs invertus, bronchiectasis, recurrent sinusitis, and infertility?

Back 27

kartagener's syndrome

Front 28

list the collegen types, and defects/important facts associated with them

Back 28

1 - bone, skin, tendon, cornea - osteogenesis imperfecta
2 - cartilage - stain with safranin O
3 - blood vessels - defective in EDS
4 - basement membrane - defective in alports syndrome

Front 29

ostegenesis imperfecta questions.
what type is fatal in utero? why do you have dental imperfections?

Back 29

type 2 fatal, dental imperfections because type 1 col makes dentin which is a component of teeth.

Front 30

what 3 organ systems can alport's involve?

Back 30

kidney, causing nephritis. eyes - causing occular disturbances, and ears, causing deafness.

Front 31

what does SNoW DRoP mean to you?

Back 31

southern, northern, western blot, looks for:
DNA, RNA, Protein.
Use southwestern blot for DNA binding protein such as transcription factor.

Front 32

example of codominance?

Back 32

blood groups

Front 33

does loss of heterozygosity refer to tumor suppressors or oncogenes?

Back 33

tumor suppressors only! oncogenes have bad outcomes with even just 1 mutation

Front 34

if patient has no active chromosome 15, what disease is this: mental retardation, hyperphagia, obesity, hypogonadism, and hypotonia.

Back 34

this is prader willi, where the patient has an already inactive MATERNAL, and PATERNAL also gets inactivated after.

Front 35

if patient has no active chromosome 15, what disease is this: laughing all the time, mental retardation, seizures, and ataxia.

Back 35

angelmans. patient already has inactive PATERNAL, and then MATERNAL gets inactivated.

Front 36

what form of dominance is the disease characterized by telangiectasia, recurrent epitaxis, skin discolorations, and ateriovenous malformations?

Back 36

autosomal dominant - hereditary hemorrhagic telangiectasia - aka osler-weber-rendu syndrome

Front 37

what does CFTR normally do with Chloride?

Back 37

in sweat, it normally reabsorbs it (which is why the sweat test checks for chloride), and in liver, lung, and pancreas it normally secretes it!

Front 38

what type of mutation is observed in duchenne's muscular dystrophy?

Back 38

x-linked recessive FRAMESHIFT.

Front 39

what is this referring to? X-girlfriends, first aid, helped ace my test

Back 39

trinucleotide repeats and the middle letter of the repeat
X - fragile X (CGG)
F - fredrich's ataxia (GAA)
H - huntingtons (CAG)
M - Myotonic Dystropy (CTG)

Front 40

where is the deletion in william's disease? features are extreme friendliness, elfin facies, hypercalcemia

Back 40

chromosome 7, microdeletion of region containing elastin gene.

Front 41

what are the two drugs that can act on ethanol metabolism?
What drugs cause disulfaram like reaction>

Back 41

fomepizole (inhibits alcohol dehydrogenase), and disulfaram (inhibits acetylaldehyde dehydrogenase)
The following drugs cause DLR: metro, 1st generation sulfonylureas, procarbazine, and certain cephalosporins.

Front 42

what happens to the NADh/NAD ratio in alcoholics?

Back 42

NADH/NAD is severely increased, causing the following diversions:
Pyruvate to lactate, and OAA to malate.

Front 43

what do heme synthesis, urea cycle, and gluconeogenesis have in common?

Back 43

all take place in mitochondria and cytoplasm.

Front 44

What are the two enzymes that can cause disorders of fructose metabolism? What sx does it cause?

Back 44

deficiency in fructokinase, and aldolase B. Aldolase B is worse. It is supposed to convert Fructose - 6 - phosphate into DHP + glyceraldehyde, and not being able to causes phosphate trapping, leading to impaired glycolysis and hypoglycemia!

Front 45

what two enzymes can cause disorders of galactose metabolism? Which is worse?

Back 45

galactokinase, and galactose-1-phosphate uridyltransferase.

galactokinase is relatively benign, presents with trouble tracking objects and a failure to develop a social smile, and could lead to infantile cataracts. however the other deficiency could lead to failure to thrive, jaundice, and mental retardation, in addition to the symptoms listed above. The symptoms can be attributed to galactiolol, which is what galactose is converted to if the two enzymes above don't work via aldose reductase. accumulation of galactilol causes the infantile cataracts.

Front 46

What enzyme builds up as a result of hyperglycemia in diabetic patients causing osmotic damage?

Back 46

sorbitol. glucose is converted to sorbitol via aldose reductase. only the liver, ovaries, and seminal vesicles have the enzyme sorbitol dehydrogenase to convert sorbitol to fructose, the other organ systems just allow it to accumulate leading to osmotic damage.

Front 47

Which two amino acids are required during growth?

Back 47

arg and lysine

Front 48

is CPS-1 or OTC the rate limiting step in UREA cycle? differentiate between the genetics of each disease, and manifestations.

Back 48

CPS-1 is rate limiting.
OTC is x-linked recessive and the most common one, and CPS is autosomal recessive.
OCT deficiency results in excess carbomyl phosphate which is converted to orotic acid. You can differentiate this from orotic aciduria by the presence of hyperammonemia

Front 49

What amino acid do the following molecules come from?

Seratonin
Heme

Back 49

Seratonin comes from tryptophan (need BH4)
Heme comes from Glycine (need B6)

Front 50

In the catacholamine synthesis pathway, what is vitamin C required for?

Back 50

Conversion of NE from dopamine.

Front 51

Glycogen storage diseases:

which causes cardiomegaly and leads to early death?

Back 51

deficiency in lysosomal a-1,4 glucosidase, which breaks down glycogen into Glucose + phosphate directly. LYSOSOMAL DISEASE - POMPE'S

Front 52

Glycogen storage diseases:

Which causes severe fasting hypoglycemia, and increased blood lactate along with increased glycogen in the liver leading to hepatomegaly?

Back 52

Glucose - 6 - phosphatase deficiency (von-gierke's)

Front 53

Glycogen storage diseases:

which one causes muscle fatigue, due to increased glycogen in muscle, and an ibaility to break it down? also causes myoglobinuria!

Back 53

glycogen phosphorylase in the muscles - mcardle's disease

Front 54

Which is the only x-linked lysosomal storage disease?

Back 54

FABRY'S - deficiency in a-galacosidase A, and causes ceramide trihexoside to accumulate. Will present with peripheral neuropathy and angiokeratomas, which are scars between the umbilicus and knees.

Front 55

Which is the most common lysosomal storage disease?

Back 55

Gaucher's disease - deficiency in glucocerebrosidase, leading to increase glucocerebroside.
FIndings include aseptic necrosis of femur leading to bone crisis, and Gaucher's cells, which are macrophages that look like crumpled tissue paper.

Front 56

which lysosomal storage disease causes progressive neurodegeneration, and allows visualization of a cherry red spot on the macula?

Back 56

Neimann-pick - deficiency in sphingomyelinase, leading to increased sphingomyelin which accumulates in macrophages causing the characteristic foam cells. Babies usually die before the age of 3.

Front 57

How can you differentiate between Neimann picks vs tay sachs?

Back 57

They both cause death really early, but tay sachs wont have hepatosplenomegaly, or foam cells. instead it has lysosomes with onion cells. The defect is in hexoaminidase A, leading to accumulation of GM2 ganglioside.

Front 58

Which Lysosomal storage disease leads to central AND peripheral neuropathy?

Back 58

Metachromatic leukodystrophy, due to deficiency in arylsulfatase A, and increased cerebroside sulfate.