Flashcards in Biochemistry - UWorld Deck (66)
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
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.
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
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
Examples of molecules that use the PLC signalling pathway
alpha1, M1, M3, V1, H1, oxytocin, AT II, TRH, GnRH
How is NO synthesized?
Arginine + O2 is converted to NO by NO synthase
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.
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.
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.
Why are cancer cells immortal?
They have high telomerase activity and do not undergo cell death initiated by shortening of their telomeres.
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
Cheilosis, corneal vascularization
Vitamin C overdose
False negative stool guiac, bloating
Vitamin E overdose
Hemorrhagic stroke and infant NEC
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)
Two alpha and two gamma chains. Replaces all embryonic Hgb by 14 weeks.
Two alpha and two delta chains
Factors that promote RBC sickling
Anoxia, acidity, 2,3-BPG binding and hypovolemia
What form of Hbg is stabilized by 2,3-BPG
Taut, this results in decreased Hgb affinity for O2 and increased peripheral O2 unloading
5 factors required by branched chain alpha-ketoacid dehydrogenase, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase
"Tender Loving Care For Nancy"
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.
Homeobox genes code for...
DNA transcription factors that govern the proper placement of appendages
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.
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.
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.
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.
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.
Principle forces stabilizing secondary protein structure
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.