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NBME#3 block 1 Q1----------------------Q50 - maryam2009
#1
Please choose and answer the Qs in order.Thank you
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#2
q 1. liver cells of infant ??

q2 . carnitine - palmitate

q3 . e.tyrosine
q4. ?

q5. e spleen
q6 .h .THF -alpha
q7 >.hyponatremia (siadh )????


q8 .a (megaloblastic anemia )

q9 .c -jak/stat

q10 .a(depletion of glutathione stores
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#3
Welcome to the NBME 's Qs block,
Please answer the Qs with the explanation and then if you like to bring some Qs to an open discussion, post a new message in a separate page then add the best and correct explanation to this page. The aim of making this block is having the explanations of correct answer,because most of us have the key answer .Thank you.
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#4
1.B
transcription factor (sometimes called a sequence-specific DNA-binding factor) is a protein that binds to specific DNA sequences, thereby controlling the movement (or transcription) of genetic information from DNA to mRNA.
Transcription factors perform this function alone or with other proteins in a complex, by promoting (as an activator), or blocking (as a repressor) the recruitment of RNA polymerase (the enzyme that performs the transcription of genetic information from DNA to RNA) to specific genes.
Transcription factors are essential for the regulation of gene expression and are, as a consequence, found in all living organisms.Not only do transcription factors control the rates of transcription to regulate the amounts of gene products (RNA and protein) available to the cell but transcription factors themselves are regulated (often by other transcription factors).

Transcription factors (like all proteins) are transcribed from a gene on a chromosome into RNA, and then the RNA is translated into protein. Any of these steps can be regulated to affect the production (and thus activity) of a transcription factor.

please post more explanation,because I couldn't find specific answer for it.


2.D

Carnitine is a hydrophilic natural substance acquired mostly through dietary meats and dairy products and is used by cells to transport hydrophobic fatty acids. The "carnitine shuttle" is composed of three enzymes that utilize carnitine to facilitate the import of hydrophobic long-chain fatty acids from the cytosol into the mitochondrial matrix for the production of energy via β-oxidation.

Carnitine palmitoyltransferase I (CPT I) is localized to the outer mitochondrial membrane and catalyzes the esterification reaction between carnitine and palmitoyl-CoA to produce palmitoylcarnitine. Three tissue-specific isoforms (liver, muscle, brain) have been identified.

Carnitine-acylcarnitine translocase (CACT) is an integral inner mitochondrial membrane protein that transports palmitoylcarnitine from the intermembrane space into the matrix in exchange for a molecule of free carnitine that is subsequently moved back out of the mitochondria into the cytosol.
Carnitine palmitoyltransferase II (CPT II) is a peripheral inner mitochondrial membrane protein ubiquitously found as a monomeric protein in all tissues that oxidize fatty acids.[7] It catalyzes the transesterification of palmitoylcarnitine back into palmitoyl-CoA which is now an activated substrate for β-oxidation inside the matrix.

3.E

Phenylalanin....Tyrosine.....1.Thyroxine ,,,, 2.Dopa....1.Melanin,,,,2.Dopamine....NE...EPi

4.A??
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#5
Q1.B
raheem - 03/15/11 22:31

sequences responsible for transc. regul. are promotor(normal level transcr.)and enhancer(high level transcr.) AND REPRESSOR(LOW LEVEL TRANSCR.) SO TRANSCRIPTION FACTORS WILL ACTIVATE ANY ONE OF THOSE SEQUENCES ACCORDING TO CELL NEEDS SO IN INFANT THERE IS RAPID GROWTH THAT MEAN TRANS. FACTER WILL ACTIVATE ENHANCER
,,,THAT WHY ANSWER IS ,,,C,,,,COZ TRANS. FACTER IS MAJOR FACTOR DECID RATE OF GROWTH,,,,,,,,,,,,,,,,,,,

5.E
The foregut is the anterior part of the alimentary canal, from the mouth to the duodenum at the entrance of the bile duct. At this point it is continuous with the midgut. Pain in the foregut is typically referred to the epigastric region, just below the intersection of the ribs.

Structures of the foregut are:

Esophagus
Stomach
Duodenum (1st and 2nd parts)
Liver
Gallbladder
Pancreas
Spleen (Note that it is located in the foregut region, but is not a gut organ)
Superior portion of pancreas
Arterial supply to all these structures is from the celiac trunk, and venous drainage is by the portal venous system. Lymph from these organs is drained to the prevertebral celiac nodes at the origin of the celiac artery from the aorta.

The midgut is the portion of the embryo from which most of the intestines develop. After it bends around the superior mesenteric artery, it is called the "midgut loop". It comprises the portion of the alimentary canal from the end of the foregut at the opening of the bile duct to the hindgut, about two-thirds of the way through the transverse colon.

Duodenum (distal half of 2nd part, 3rd and 4th parts)
Jejunum
Ileum
Cecum
Appendix
Ascending colon
Hepatic flexure of colon.
Transverse colon (proximal two-thirds)
Vascular, lymphatics and innervationArterial supply to the midgut is from the superior mesenteric artery, an unpaired branch of the aorta. Venous drainage is to the portal venous system. Lymph from the midgut drains to prevertebral superior mesenteric nodes located at the origin of the superior mesenteric artery from the aorta. Portal drainage carries all non-lipid nutrients from digestion to the liver for processing and detoxification, while lymphatic drainage carries fatty chyle to the cisterna chyli. Autonomic innervation of the midgut is from the superior mesenteric plexus.

The hindgut (or epigaster) is the posterior (caudal) part of the alimentary canal. In mammals, it includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum
Blood flow :Arterial supply is by the Inferior mesenteric artery, and venous drainage is to the portal venous system. Lymphatic drainage is to the chyle cistern.

Wikipedia






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#6
6.H

Tumor necrosis factors (or the TNF-family) refers to a group of cytokines family that can cause cell death (apoptosis).

1.Tumor necrosis factor-alpha (TNF-αWink is the most well-known member of this class, and sometimes referred to when the term "tumor necrosis factor" is used.

2.Tumor necrosis factor-beta (TNF-βWink, also known as lymphotoxin is a cytokine that is inhibited by interleukin 10

It can cause cytolysis of certain tumor cell lines;
it is involved in the induction of cachexia;
it is a potent pyrogen, causing fever by direct action or by stimulation of interleukin-1 secretion; finally,
it can stimulate cell proliferation and induce cell differentiation under certain conditions.

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#7
guys, it seems like we have different NBMEs, since my Qs don't match.
@maryam, I would love to discuss Qs with you, if you could send your form to me, I would really appreciate it. My email icbcc
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#8
7.C
small cell...Oat cell....>with ectopic produstion of ACTH and ADH.

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#9
4.A
drona99 - 03/15/11 23:44

To answer these kind of qs we shud know some of the following osmoles and their corresponding concentration .


OSMOLES -------------------------------CONCENTRATION OF ALL PARTICLES

1-100 m M/L of Nacl -----------------------------------200 mosm/L

2-100m M/L of glucose ---------------------------------100 mosm/L

3- 100m M/L of CaCL2------------------------ ------------3mosm/L

4-100mM/LNacl +100mM/L urea -----------------------------300mosm/L



mosm = milliosmolar or mosm/L = is aindex of concentration of particle per liter of solution

mM =millimolar or mM/L =an index of concentration of molecules dssolved per liter of solution.

Isotonic solution =300mosm=150 mM [becoz one molecule of NACL yields two particles in solution]

1-Now when u add hypotonic solution of ECF - then effective osmolslity decreases that leads to movement of water in to the cell-- cell will swell

2- when we add hypertonic sol to ECF - then effective osmolality increases that leads to movement of water out of the cell -- cell will shrink


coming back to q
After adding NACL solution cell volume has increased from 1 to 2 that means we must has added hypotonic solution that correlates with option A ie 75 mM ==150 mosm

option B 150 mM= 300 mosm = isotonic no movement of water

option c 300mM=600mosm;500mM=1000mosm,1500mM=3000osm all hypertonic cell will shrink and decrease in volume .
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#10
drona99 - 03/16/11 00:10
8.A

old woman with dyspnoe and fatigue
lab s/o anaemia and low WBCs and platelets and peripheral smear showd hypersegmented nuetrophills ..answer is AA antibodies against antiparietal cells.

pthogenesis of vitamin b12 or folate def,

A--Impaired DNA synthesis
1-Delayed nuclear maturation
Causes a block in cell division leading to large, nucleated hematopoietic cells
Enlarged cells are called megaloblasts.
2-Affects all rapidly dividing cells
Examples-RBCs, leukocytes, platelets, intestinal epithelium

3-Cellular RNA and protein synthesis continue unabated.
Cytoplasmic volume continues to expand.

2----Ineffective erythropoiesis
Megaloblastic precursors outside the bone marrow sinusoids are phagocytosed by macrophages.
Megaloblastic precursors undergo apoptosis causing pancytopenia.
Anemia, neutropenia, and thrombocytopenia

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