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Flashcards in Biochemistry - UWorld Deck (66)
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1

Proteins transcribed by the lac operon

Lac Z = beta-galactosidase, hydrolyzes lactose to glucose and galactose

Lac Y = permease, allows lactose to enter the bacteria

Lac p = binding site of RNA polymerase

Lac I = constitutively produces Lac repressor protein, lactose binds this and prevents the repressor from binding to the operator site

2

Glucose's effects on the lac operon

Glucose increases intracellular ATP levels, which deactivates adenylate cyclase, reduces cAMP levels and reduces CAP binding to the promotor region.

3

Consequence of the deltaF508 mutation that causes cystic fibrosis

This results in improper posttranslational folding and shunting of the improperly folded protein to the proteosomes instead of the epithelial membrane

4

Protein mutation in the Ras-MAP kinase pathway that commonly predisposes to cancer.

Mutation in Ras that makes it resistant to GTP hydrolysis or mutation in GAP that cannot hydrolyze GTP results in constitutive activation of Ras leading to overactivation of genes and cancer

5

Examples of molecules that use the PLC signalling pathway

alpha1, M1, M3, V1, H1, oxytocin, AT II, TRH, GnRH

6

How is NO synthesized?

Arginine + O2 is converted to NO by NO synthase

7

Proteins that can be labeled by a DNA probe

Proteins that can actually bind DNA: transcription factors (n-myc), steroids, thyroid proteins, vitamin D receptors, retinoic acid receptors, DNA replication and transcription proteins.

8

Clinical signs of OTC deficiency

Elevated carbamoyl phosphate, orotic aciduria (due to shunting of carbamoyl phosphate to thymine synthesis), neurological disorders and elevated serum NH3.

9

Components of telomerase

Reverse transcriptase component: TERT
RNA template: TERC
TERT repeatedly reads TERC TTAGGG to add telomeres to the end of DNA and does not need a template.

10

Why are cancer cells immortal?

They have high telomerase activity and do not undergo cell death initiated by shortening of their telomeres.

11

Consequence of vitamin A toxicity

Acute: nausea, vomiting, vertigo, blurred vision
Chronic: alopecia, dry skin, HLD, hepatoxicity, HSM and vision complaints
Teratogenic: microcephaly, cardiac abnormalities and 1st trimester fetal death

12

Riboflavin deficiency

Cheilosis, corneal vascularization

13

Vitamin C overdose

False negative stool guiac, bloating

14

Vitamin E overdose

Hemorrhagic stroke and infant NEC

15

Embryonic hemoglobin in the yolk sac

Two zeta and two epsilon chains (Hgb Gower)
Two alpha and two epsilon chains (Gower 2)
Two zeta and two gamma chains (Hgb Portland)

16

Fetal hemoglobin

Two alpha and two gamma chains. Replaces all embryonic Hgb by 14 weeks.

17

Hemoglobin A2

Two alpha and two delta chains

18

Factors that promote RBC sickling

Anoxia, acidity, 2,3-BPG binding and hypovolemia

19

What form of Hbg is stabilized by 2,3-BPG

Taut, this results in decreased Hgb affinity for O2 and increased peripheral O2 unloading

20

5 factors required by branched chain alpha-ketoacid dehydrogenase, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase

"Tender Loving Care For Nancy"
Thiamine
Lipoate
CoA
FAD
NAD

21

2-5 month old infant with irritability, developmental delay, poor muscle tone and liposomal galactocerebroside accumulation.

Krabbe disease due to autosomal recessive deficiency in galactocerebrosidase.

22

Homeobox genes code for...

DNA transcription factors that govern the proper placement of appendages

23

Adult with arthritis and blue-black deposits in the cornea and aricular cartilage. His urine sample turns black when exposed to air.

Alkoptonuria due to deficiency in the enzyme homogentistic acid dioxygenase. Accumulation of homogentistic acid results in these black-blue deposits.

24

18 month old who developed normally, but suddenly lost motor and language skills and constantly wrings her hands. Physical exam reveals decreased head size.

X-linked MECP2 mutation causing Rett syndrome.

25

Enzyme that increases use of PRPP in patients with Lesch-Nyhan syndrome

PRPP amidotransferase, this is because deficient HGPRT results in increased requirement for de novo purine synthesis, which goes through this enzyme.

26

A patient has acroparesthesia, acrokeratomas (dark red, non-blanching macules/papules between umbilicus and knees) and culture demonstrates failure to metabolize ceramide trihexose. What will likely result in this patient's death?

Fabry disease due to inherited deficiency in alpha-galactosidase A. This results in accumulation of the globoside ceramide trihexose in tissue and patients die from renal failure if this enzyme is not supplemented.

27

How to tell failure of meiosis I vs. meiosis II on RFLP analysis for trisomy 21

Since you would inherit both sister chromatids in failure of meiosis II, there would be two bands with one band being thicker in the child. In failure of meiosis I, the child would have 3 different chromosomes.

28

Principle forces stabilizing secondary protein structure

Hydrogen bonds

29

Enzyme defect in a patient with early onset acute coronary syndrome, ocular lens displacement and intellectual disability with elevated methionine levels. Treatment?

Cystathione beta synthase. Patients cannot form cysteine from homocysteine, making cysteine an essential amino acid in their diet and homocysteine levels rise leading to hypercoaguability. Also, homocysteine buildup can result in hypermethioninemia. Treat with methionine restriction and pyridoxine (vitamin B6) supplementation to augment cystathione synthase's activity.

30

Type II glycogen storage disease

Pompe disease: