Official NBDE Part 1 Study Q & A Thread

This Q was originally posted by rayman on 4-18-2010 in the thread -
Lets discuss Q's of NBDE 1 (which is still open but locked for new posts)
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By rayman
hi
which of these is a nucleotide?
A-RIBOSE
B-URACIL
C-ADENOSINE
D-THYMIDYLATE
THANK IN ADVANCE
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@ rayman - Ans- D-THYMIDYLATE

 

Nucleotide= Nitrogen Base + Sugar+ phosphate, dTMP or deoxyribose thymidinne monophosphate is also referred to as thymidylate.

 

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As part of an experimental study, a volunteer agrees to have 10 grams of mannitol injected intravenously. After sufficient time for equilibration, blood is drawn and the concentration of mannitol in the plasma is found to be 65mg/100 mL. Urinalysis reveals that 10% of the mannitol had been excreted into the urine during this time period. What is the approximate extracellular fluid volume of this volunteer?


A. 10 L

B. 14 L

C. 22 L

D. 30 L

E. 42 L

 

I am not sure if these type of questions appear or not on the test, but it sure did take me a lot of research to find the answer. I really an not a fan of physics so I hope we don't get many of them on the real test.

According to the equation for calculating Extracellular fluid:
V = (M - MU) / C
Where V is the volume of the body fluid compartment, M is the mass of marker injected, MU is the mass of marker lost in the urine during equilibration and C is the measured concentration of the marker.

So according to the above equation, the answer would be 13.8 liters which is closest to answer B-14 L. Hope this helps, but what a question!! Does anyone know if we will get questions like that on the real test?? If so are they a lot? Should we review more of these equations?? THanks!

 

Thanks.

The ability to concentrate urine varies among animal species. The max urine conc that can be produced by an animal is MOST closely relate to which of the foll:
a. renal blood flow
b. total number of nephrons
c. gfr
d. length of loop of henle
e. diameter of distal tubule

 

I am thinking it's d. as the contercurrent mechanism for concentrating urine depends on the thick ascending loop of henle and the resorption of Na, K, and Cl into the medulla. If you have another answer please share. I might be wrong.

 

You are right. Thanks. How would you explain this:

Insulin increases the activity of which of the foll:
a. enolase
b. phosphorylase
c. PFK
d. glucose 6 phosphatase
e. fructose 16 diphosphatase

 

The ability to concentrate urine varies among animal species. The max urine conc that can be produced by an animal is MOST closely relate to which of the foll:
a. renal blood flow
b. total number of nephrons
c. gfr
d. length of loop of henle
e. diameter of distal tubule

 

Hey Jalika,

Let's think this through, So insulin has an anabolic effect right? So it tends to favor glucose transport, uptake and glycogen syntheses. So if we look at the answers give. I would say insulin inhibits gluconeogenesis enzymes which are d & e. It also inhibits glycogen breakdown. SO it inhibits glycogen phosphorylase, so there goes answer b. My guess would be that it stimulates glycolysis and break down of glucose in the target cell.I think the answer is (c). Please anyone correct me if I am wrong.

 

yes u are right..insulin stimulate phosphofructosekinase and glucagon inhibit it.PFK-1 is also inhibited by citrate and ATP.

 

volume=(amount injected-amount excreted)/concentration

 

answer should be DIAMETER OF DIS TUBULE
because more the diameter of dis tubule more surface area will be avilable for water absorption........and final urin concentration occures in distal tubule by action of ADH....I have also seen this question somewhere but don't remember where? correct me if i m wrong

 

the answer should be loop of henley cause the highest osmolar conc of the urine occurs in the loop of henley and if its length is increased it would def help it..this is applied in desert animals whose loop of henley length is increased as to facilitate increased water reabsorption..

 

yes, you are right.the answer should be loop of henley

 

Previous ​

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studies on the mammalian kidney have indicated that the ability to
concentrate urine is related to three main structural features. The first, and apparently​

the ​

​

​

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most important, is the relative thickness of the medulla. This is an index
of both the length of the loops of Henle, which act as a countercurrent multiplier
system, and of the length of the vasa recta, which act as a countercurrent exchange
system. Schmidt-Nielsen & O'Dell (1961) found that the relative medullary thickness​

in ​

​

​

​

various mammalian species varied directly with the ability to produce hypertonic​

urine. The minimum value was found in beavers (1 3), the maximum in the water

u r right....i got it....


please can u tell me where is this que from?

AND ALSO I WANNA KNOW HAVE U GUYS TAKEN YOUR DATE FOR PART-1?

 

it was taken from the testlet I-K.

 

ANS: RENAL BLOOD FLOW
I see a lot of different choices of ans have been chosen for this question. BUT the right ans is -Renal blood flow.
*There about 500,000 nephrons in each kidney under normal conditions.
*GFR depends on the renal blood flow (glomerular filtrate is formed by squeezing fluid through the glomerular capillary bed by the driving hydrostatic pressure (head of pressure) controlled by the afferent and efferent arterioles, and provided by arterial pressure)
*Agreed that the highest osmolar conc of the urine occurs in the loop of henley - Vasa recta and henley work together to conc the urine by counter current mech -which depends on the amount and osmolality of blood flowing through the peritubular capillaries surrounding the tubules.
*Inside the distal and collecting tubules, the filtrate is either diluted or concentrated to form urine regulated by ADH- which again depends on the osmolality.
The ability of the kidneys to selectively clear waste products from the blood and simultaneously maintain the body’s essential water and electrolyte balances is controlled in the nephron by the following functions: renal blood flow, glomerular filtration, tubular reabsorption, and tubular secretion
Mechanisms for urinary conc or dilution depend on counterflow processes, both tubular and vascular, within the renal medulla.The regulation of plasma osmolality is accomplished by varying the amount of water excreted by the kidneys. It is due to the response to water deprivation or to water intake. When the osmolality is too low, nervous and hormonal feedback mechanisms cause the kidneys to excrete a great excess of water in urine causing a dilute urine, but removes water from the body to increase the body fluid osmolality back to normal. When the osmolality of body fluids is too great, the kidneys excrete an excess of solutes to reduce the body fluid osmolality again back to normal, but at the same time excreting a concentrated urine.
Maintenance of water balance is tightly regulated by renal functions such that water intake precisely match water loss from the body. Low water intake or increased water loss results to small vol of conc urine produced by the kidneys to conserve water. Human kidneys have powerful capability to retain water such that the vol of urine excreted may represent less than 1% of the volume of glomerular filtrate. In cases of increased water intake or over hydration, large vol of dilute urine is produced. Water reabsorption occurs passively in several parts of the nephron. Permeability to water by the distal tubule and collecting ducts is regulated by ADH. The rate of release of this hormone from the posterior pituitary gland is in turn affected by changes in fluid intake, or fluid loss from the body, consequently changing the rate of water excretion

 

Hey dentdoc,
i think they are right on the countercurrent multiplier and length of loop of Henle..
i have a question here
In the molar, the rootcanals usually join the pulp chamber
a) at level of furcation
b)at varying levels depending on age
c)within the cervical third of crown
d)apical to cervical level of crown

Key ans is c.. decks answer is d... plz explain

 

Its PFK... in the liver once the ATP has been generated and Citrate levels hv risen thnx to the Krebs cycle.. inorder to synthesize fatty acids the insulintakes over --> generation of PFK2---> production Fructose 2, 6 bisphosphate.. this complex overrides the negative effects of Citrate and ATP on PFK1 and the glycolysis continues to produce Acetyl Co A which the in turn produces Acetyl Co A----> Fatty Acid Synthesis

 

Very interesting Insulin also is responsible for the glycogen synthase which results in storage of glucose as glycogen.. so it simultaneously activate two contradicting enzymes in presence of excess glucose.. PFK2 and glycogen synthase!! probably the initial response is to increase the glycogen stores

 

hey correct ans should be D........
i have seen this que at 2 different spaces......and ans is different at both places......i have confirmed in willers.....

 

What kind of fungal infection affects reticuloendothelial cells


What hormone acts slowly and acts on intracellular receptors? Estrogen
(I dont think estrogen is the correct answer, is it)

Know about the axis in pacemaker recording.
(is this asking about p qrs and t?)

What ganglion has unipolar (pseudounipolar) neuron? Choices were otic, ciliary, submandibular etc.


Lots of question comparing max central incisor with max canine
(what can they ask?)

Failure of fusion in what processes causes oblique clefting of the face

Insulin and IGF have what in common? tyrosine kinase receptor, membrane receptor (I think its tyrosine kinase...but basically they were trying to ask what kind of second messenger is used)


Help me answer these questions and I will post more to help everyone!

Thanks!

 

Ans: Histoplasmosis - H. capsulatum
The dimorphic yeast cells are found within the macrophages

 

Failure of the lateral nasal process to fuse with the maxillary process leaving the nasolacrimal duct exposed. It can occur along with a cleft lip

 

Essentially fungal infections such as cryptococcosis, coccidiomycosis, blastomycosis and histoplasmosis are granulomatous diseases

 

Dorsal root ganglion (sensory ganglion in spinal cord) has pseudounipolar neurons

Tyrosine kinase ( auto phosphorylates)... Phospholipase C.. second messenger, also something on ras.. not sure.. will read up

Plz do not post such questions.. or dr tinman will... shut us down... )

But you are free to clear any doubts..

 

Thanx Dr Bunty

 

What hormone acts slowly and acts on intracellular receptors? Estrogen
(I dont think estrogen is the correct answer, is it)


yes its estrogen coz estrogen is steroid and steroid hormones always act on intercellular receptors and they are slow coz they have to go through the procesess of making new proteins to act.its take time.

 

All hormones that act on Intracellular receptors are slow acting and increase the rate of gene expression - Steroid H ( cortisol, estrogen, progesterone, testosterone), Vit A & Vit D derivatives, Thyroid H

Insulin, IGF and Platelet derived growth factor (PDGF) dont use 2nd msg'ers. Tyrosine kinase receptor, a cell surface/transmembrane receptor is common to all three

 

Pure rotation of the mandible involves which two planes of movement?
Frontal
Horizontal
Saggital

The correct answer per Decks is Frontal and Sagittal.

Can somebody explain the answer including why horizontal is not right?
Thanks

 

16. The Sanger method of cloning uses
-transcription
-translation
-reverse transcriptase

17. Intermediate in synthesis of cholesterol
-squalene
-doxycholine
-choline


12. Sucrose DIRECTLY contributes to plaque by
-polysaccharides
-glycolytic enzymes
-mucin


10. What type of hemoglobin do diabetic patients have?
-HbF
-HbA
-HbAic
-HbS

11. Most abundant proteoglycan in teeth
-chondroitin sulfate
-hyaluronate


1. Methylated labile protein
-THF
-SAM
 (i think) -methionine

2. AA with hydroxyl group
-serine
-alanine
-arginine (i think)


24. Cigarette smoking does not contribute to the cancers in: larynx, stomach, esophagus, pancreas, bladder


IgG is activated where?

1. Bacteria lacking catalase are sensitive to ... oxygen or superoxide ion or hydrogen peroxide?

 

h2o2

 

what immediately covers a myofibril?


risk factor for development of endometrial carcinoma

orgin of trigeminal n

communication from facial vein to cavernous sinuse?

if posterior crossbite which cusps would contacts in mediotrussive movement???

muscles with least regenerative capacity

if V nerve is cut below medulla what happens

loss of sensation of pain same side
loss of pain ipsilateral
loss of propioception same side
loss of sensation of propioception opposite side

sensory nucleus for 5 6 9 7 and 10 is

 

hope this helps

 

1 L question 363.. plz explain
42 year old lady with hyperparathyroidism.....
Which will be most likely increased in this case??
My answer.. Ca absorption..
Key answer, renal Ca excretion... why???

 

Pseudounipolar nerve cells.. trigeminal ganglion

 

yes hyper parathyroidism also increase ca absorption........

because of osteoclastic activity ca level of blood is so high...kidney reabsorb ca as maximum as it can but it's still beyond it's absorption capacity....so excess will be excreted.....

 

Thnx

 

serous demilunes secrete into: intercalated ducts, striated ducts etc.?

FL longitudinal section of canine is taken, where is the widest portion of the pulp chamber? Medial 1/3 or cervical 1/3


Where is pain from the orofacial region sent to? Nucleus ambiguous, nucleus dorsal, some other choices, inferior olive


A dentist loses a tooth, where should he not look for it? Vallecula, piriform recess, pharyngeal recess, and something else by the larynx


Where is testosterone made…not which cell, but where in the system, seminiferous epithelium?


Crypts of lieberkuhn are in what layer of the SI? Muscularis externa, adventitia, submucosal?


Anterior superior most position of condylar head is known as: centric relation
I know CR is posterior superior what is anterior superior?


To get to submandibular duct you need to cut through: mucosa only
shouldnt it be mylohyoid or something?


Two questions on which groove is bigger max 2nd pm or max 1st pm, and which has more supplemental grooves


What stimulates the ectoderm to turn into neural crest?

 

What is key charac about mand 1st molar? Mesiolingual developmental groove

this isnt right because isnt that the key characteristic of max first molar and premolar?


Cortical plate histologically has: I don’t remember, one answer was Whorling bone

blood supply of condyle?


fumarate is in what two pathways


which of the following when metabolized is largest drop in free energy? Creatine phosphate, glucose 6 phosphate i think its this

 

Hi guys,

I need help with this question:

The apices of a mandibular second molar are located:


a-posteriorly to ptergomandubular raphe
b- inferiorly to mylohyoid muscle insertion
the other 2 are not correct. Which one is it?? the answer key says b but could it be (a) too? what do u think??

 

when's your exam??

 

Should be glucose 6 phosphate.. not sure

 

some facts abt hemoglobin in diabetics , it's HbA1c(not HbAic)

Glycated hemoglobin (glycosylated hemoglobin, hemoglobin A1c, HbA1c, A1C, or Hb1c; sometimes also HbA1c) is a form of hemoglobin which is measured primarily to identify the average plasma glucose concentration over prolonged periods of time. It is formed in a non-enzymatic glycation pathway by hemoglobin's exposure to plasma glucose. Normal levels of glucose produce a normal amount of glycated hemoglobin. As the average amount of plasma glucose increases, the fraction of glycated hemoglobin increases in a predictable way. This serves as a marker for average blood glucose levels over the previous months prior to the measurement

 

ans should be creatin phosphate.......
because delta G is measurement of release of energy in reaction.....creatin phosphate contain maximum energy in it's phosphate bond so it will release maximum energy....and the drop of free energ of substance will me maximun

anaita have u taken the date for test?......

 

Ans : Inferior to mylohyoid muscle insertion.
Pterygomandibular raphe is attached to the posterior end of mylohyoid line which ends slightly posterior to the 3rd molar, posteriorly. So, 'No' it cant be (a) also

 

thnx... will read that up..., could nyone plz give me a reference for the facial spread of infections; i mean the spaces... dont have an OS book around..
yeah.. june it is.. what about you?? when's your exam scheduled for??