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* NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 08:38
  Hello All, since it seems there isn't an available thread discussing and explaining the answers like maryam2009 and sarim used to post of NBME 13, i'll be posting them following this order---> Posted by @larva.

Link to Block 1 Discussion:

Please feel free to add and help w/ the explanations.

Thank you.
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 13:05
Answer: A

Open-ended questions are preferable.


Proteasomal degradation: Attachment of Ubiquitin to defective protein to tag them for breakdown. Ubiquitin is a protein ligase. The proteasome recognize these ubiquinated proteins uses ATP energy to drive them through its tubular structure, degrading them into small particles.
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 13:10
Answer: F

Liver disease is a/w hyperstrenism (arises from decrease catabolism of estrogen, increase SHBP globulin (which decrease free testosterone/estrogen ratio)), which will lead to hypogonadism, resulting in decrease testosterone like in this case.
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 13:37

Muscle atrophy occurs by a change in the normal balance between protein synthesis and protein degradation
During atrophy, there is a down-regulation of protein synthesis pathways, and an activation protein degradation

via @my250
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 13:37
Missing from file
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 13:42
Answer: E

Chronic alcohol use is an inducer of p450 system.

Clomiphene: act as partial estrogen agonist, inhibits stronger estrogen negative feedback on the secretion of gonadotropins, enhacing release of then and stimulating ovulation.
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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/03/13 16:11
  Missing Q's from block 2:

A 60-year-old man comes to the physician because of a 2-week history of fatigue and exercise intolerance. One month ago, he was diagnosed with stage 1 HTN and began treatment with propranolol. His pulse is 56/min, compared with 72/min 1 month ago. His treatment is switched to pindolol. His symptoms resolve within 1 month, and his pulse is 68/min. Which of the following mechanisms of action of pindolol best explains its effect on this patient's heart rate?
A) Competitive agonism
B) Competitive antagonism
C) Inverse agonism
D) Partial agonism

Ans: D) partial agonism

An investigator studying the molecular events in the underlying causes of an autoimmune disease develops a collection of monoclonal antibodies to ribosomal proteins. One of the monoclonal antibodies is found to inhibit the ribosome peptidyl transferase. Which of the following is most likely affected in the presence of this antibody?
A) Assembly of 80S ribosomal subunits
B) Attachment of amino acids to tRNA
C) Dissociation of the 80S ribosomes into 60S and 40S subunits
D) Establishment of covalent bonding between amino acids
E) Release of the mRNA from ribosomes

Ans: D) Establishment of covalent bonding between amino acids

A 9-year-old boy is brought to the ED because of fever, chest pain, and migratory joint pain in his shoulders, hips, and knees for two days. Four weeks ago, he had a febrile pharyngitis, which resolved 2 weeks without treatment. His temperature is 39C. The lungs are clear to auscultation. A pericardial friction rub and quiet heart sounds are heard. Throat cultures do not grow any pathogens. Laboratory testing shows increased antibody titers to streptolysin O. The greatest risk for death at this time is from which of the following?
A) Aortic stenosis
B) Embolism
C) Mitral insufficiency
D) Myocarditis
E) Septic shock

Ans: D) Myocarditis

A young adult couple has been unable to conceive for the past two years. The woman has regular menstrual cycles and takes no contraceptives. A semen analysis shows:
Quality: Normal range
Quantity: Normal range
Color: White
Fructose: 5% of normal content
The most likely cause of this couple's infertility is deficient activity of which of the following in the man?
A) Adenohypophysis
B) Bulbourethral glands
C) Prostate
D) Seminal vesicles
E) Testes

Ans: D) Seminal vesicles

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* Re:NBME 13 Discussion Block 2 q1-50
  ae0704 - 11/07/13 09:10
  ****Addition to Q#18*******
Answer: C

Desensitization of nicotinic receptor.

Cholinergic Crisis: Occurs when pte. receives inappropriately High doses of cholinesterase inhibitors and has excessive Ach in the synaptic cleft. the increase in Ach causes excessive stimulation of the Skeletal muscle and results in muscle refractory to future impulses. Also presents w/ Muscle weakness. Since neuromuscular junction becomes insensitive to Ach, an infusion of edrophonium produce No improvement of symptoms.

treatment: Discontinuation of AchE inhibitor.
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