NBME Final- Biochem + Genetics Exam
Questions and Answers 100% Pass
Sodium-potassium
pump - answerNa+-K+ ATPase is located in the plasma
membrane with ATP site on cytosolic side.
For each ATP consumed, 3Na+ go out of the
cell (pump phosphorylated) and 2K+ come into
the cell (pump dephosphory...
pump - answer✔Na+-K+ ATPase is located in the plasma
membrane with ATP site on cytosolic side.
For each ATP consumed, 3Na+ go out of the
cell (pump phosphorylated) and 2K+ come into
the cell (pump dephosphorylated).
Ouabain inhibits by binding to K+ site.
Cardiac glycosides (digoxin and digitoxin)
directly inhibit the Na+-K+ ATPase, which
leads to indirect inhibition of Na+/Ca2+
exchange > ^ [Ca2+]i > ^ cardiac contractility
Type I Collagen - answer✔Most common (90%)—Bone (made by
osteoblasts), Skin, Tendon, dentin, fascia,
cornea, late wound repair.
Type I: bone.
decreased production in osteogenesis imperfecta type I.
Type II Collagen - answer✔Cartilage (including hyaline), vitreous body,
nucleus pulposus.
Type III Collagen - answer✔Reticulin—skin, blood vessels, uterus, fetal
tissue, granulation tissue.
Type III: deficient in the uncommon, vascular
type of Ehlers-Danlos syndrome (ThreE D).
Type IV Collagen - answer✔Basement membrane, basal lamina, lens. Type IV: under the floor
(basement membrane).
Defective in Alport syndrome; targeted by
autoantibodies in Goodpasture syndrome.
Composition of collagen - answer✔translation of collagen α chains
(preprocollagen)—usually Gly-X-Y (X and Y
are proline or lysine). Glycine content best
reflects collagen synthesis (collagen is 1⁄3
glycine).
hydroxylation of specific
proline and lysine residues. Requires vitamin
C; deficiency > scurvy.
Osteogenesis
imperfecta - answer✔Genetic bone disorder (brittle bone
disease) caused by a variety of gene defects
(most commonly COL1A1 and COL1A2).
Most common form is autosomal dominant
with ^ production of otherwise normal type I
collagen. Manifestations can include:
-Multiple fractures with minimal
trauma A B ; may occur during the birth
process
- Blue sclerae due to the translucent
connective tissue over choroidal veins
-Hearing loss (abnormal ossicles)
- Some forms have tooth abnormalities,
including opalescent teeth that wear easily
due to lack of dentin (dentinogenesis
imperfecta)
May be confused with child abuse.
Ehlers Danlos - answer✔Faulty collagen synthesis causing
hyperextensible skin, tendency to bleed (easy
bruising), and hypermobile joints.
Multiple types. Inheritance and severity vary.
Can be autosomal dominant or recessive. May
be associated with joint dislocation, berry and
aortic aneurysms, organ rupture.
Hypermobility type (joint instability): most
common type.
Classical type (joint and skin symptoms): caused
by a mutation in type V collagen.
Vascular type (vascular and organ rupture):
deficient type III collagen.
Elastin - answer✔Stretchy protein within skin, lungs, large
arteries, elastic ligaments, vocal cords,
ligamenta flava (connect vertebrae > relaxed
and stretched conformations).
Rich in nonhydroxylated proline, glycine, and
lysine residues.
Tropoelastin with fibrillin scaffolding.
Cross-linking takes place extracellularly and
gives elastin its elastic properties.
Broken down by elastase, which is normally
inhibited by α1-antitrypsin.
Marfan Syndrome - answer✔caused by a defect in
fibrillin, a glycoprotein that forms a sheath
around elastin.
Mnemonic for Blotting Procedures - answer✔SNoW DRoP:
Southern = DNA
Northern = RNA
Western = Protein
Flow Cytometry uses - answer✔-Laboratory technique to assess size, granularity,
and protein expression (immunophenotype) of
individual cells in a sample.
-Commonly used in workup of hematologic
abnormalities (eg, paroxysmal nocturnal
hemoglobinuria, fetal RBCs in mother's blood)
and immunodeficiencies (eg, CD4 cell count
in HIV).
Fluorescence in situ hybridization (FISH) - answer✔Fluorescent DNA or RNA probe binds to
specific gene site of interest on chromosomes.
Used for specific localization of genes and direct visualization of chromosomal anomalies at the
molecular level.
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