Help explain 2 DAT achiever Bio Questions

[Peachee]

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Can someone explain these 2 bio questions from DAT achiever. I've searched the net and could find no additional explanations. 😕

Thanks

1. Why are the lower portions of loops of Henle and the collecting ducts selectively permeable to NaCl, urea, and/or water?

A. To increase the osmolarity of interstitial fluid in the cortex and help prevent water loss from the nephronic filtrate
B. To decrease the osmolarity of interstitial fluid in the cortex and help promote water loss from the nephronic filtrate
C. To increase the osmolarity of interstitial fluid in the inner medulla and help prevent water loss from the nephronic filtrate
D. To decrease the osmolarity of interstitial fluid in the inner medulla and help promote water loss from the nephronic filtrate
E. No specific reason can be deduced from the said phenomenon.

Correct Answer: C
Increased osmolarity of interstitial fluid in the inner medulla creates a hypertonic environment that facilitates water diffusing out of the collecting ducts and Loops of Henle -- a novel strategy for water conservation.

{Note that urea (a waste product) is still transported back to the ascending limbs of Loops of Henle shortly after its passive transport out of the collecting ducts.}

***I would have thought that water loss from the nephron back to the blood was promoted. That's the idea right, to make a concentrated urine?***
😕

2.
If all of the NADH molecules produced in glycolysis manage to pass on their electrons to flavin mononucleotides (FMN) of the electron transport chains, the maximum number of ATP molecules produced from one molecule of glucose will be


A. 32.
B. 34.
C. 36.
D. 38.
E. 40.

Correct Answer: D

The 2 NADHs produced by glycolysis in the cytosol are shuttled by FAD or NAD+ to the electron transport chain (ETC). Each electron passed on to FAD will be donated to ubiquinone (Q) whereas electron shuttled by NAD+ will be donated to FMN. Redox reactions cascaded from Q will end up producing 2 ATPs whereas those starting from FMN will lead to a synthesis of 3 ATPs. The total number of ATPs produced per glucose molecule ranges from 36 to 38 depending on the shuttle system involved. In the situation of the question asked, the highest limit of 38 ATPs will be generated since both electrons from NADHs are transferred to FMN.

***I don't remember FMN being involved in ETC???***

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Incidentally I think the following is a dumb question. 👎

Which of the following structures is primarily made up of microfibrils?

A. Actin or myosin
B. Centriol
C. Microtubule
D. Flagellum
E. Cellulose

Anyone want to make a guess (no cheating). I'll give the answer later.

Also Q46 implies London forces = Van Der Waal forces. This isn't really true, they are a type of Van Der Waal force. 👎

 

[Audio]

I'll answer question 1. From what I remember, you want to have high salt in the ISF in the medulla surrounding the collecting tube so that water will be reabsorbed into the body and not leave in urine.

 

[DrTacoElf]

I'll answer question 1. From what I remember, you want to have high salt in the ISF in the medulla surrounding the collecting tube so that water will be reabsorbed into the body and not leave in urine.

I agree with this but what doesn't make sense about the wording is that it says to PREVENT water loss from the nephronic filtrate. It should say PROMOTE water loss from the nephronic filtrate, which would equate to water conservation for the body.

 

[burmafrost]

either way, you would see an increase in osmolarity in the interstitium of the inner medulla so C is the best answer if you dont know anything else

 

[burton117]

Move to DAT forum?