BIO MC answer 1990

Benny Cheng Chi Fai

2010-03-27 3:50 am

Question 55

After drinking a lot of salty soup, a healthy person will produce:

A. a small volume of urine with high salt concentration

B. a small volume of urine with low salt concentration

C. a large volume of urine with high salt concentration

D. a large volume of urine with low salt concentration

Why answer is A but not C? The textbook show a paragraph that C should be
the correct answer as more water is needed to remove the salt in glomerular
filtrate and my teacher also tell me something like this as well !!!

2.If this time, the question ask what will happen after we eat a salty meal?

What should I answer? It carries 4 Marks in HKCEE!!!!!

(My teacher tells me that salt will hold more water so more urine is produced.
if I write it in HKCEE, will it be correct? )

更新1:

but why my textbook says that as both the blood and the glumerular filtrate have high salt concentration , large amount of water is needed to excrete the salt in glomerulat filtrate. so, a smaller proportion of water instead , will be reabsorbed

更新2:

Also, assume that this paragraph is correct. Why both increase in salt concentration will result in a larger proportion of water reabsorption? ( My book is Basic Principles in HKCEE Biology Book 3 by Y.K.TO) it says that it MUST be correct to be C if it is salty soup!!!

回答 (1)

[匿名]

2010-03-27 9:07 pm

✔ 最佳答案

for the second question, it depends on how much water there is in your body, if it is like the first question, then it should still be A.

for the first and second question, it says that it is a healthy person, which that person only have enough water, not too much and not too little, and so when salty foods or soup is consumed, the kidney will reabsorb most of the water back to the blood to reduce water loss, this is due to the person only has enough amount of water and so that the person cannot produce diluted urine, or the person will have not enough water in the blood or the cells in body will shrivelled due to osmosis.

2010-03-29 09:33:36 補充：
it really depends on how deep the question needs to go into, and so small volume of water will be excrete, and also, large amount of water is needed to excrete large amount of salt, but the reabsorbing of water mainly depends on the body water and salt that the body needed.

2010-03-29 09:33:43 補充：
high salt concentration in blood will need water to dissolve to diffuse inside the kidney, so large amount of water will be reabsorbed inorder for the salt to diffuse from a higher concentration in blood, to lower concentration in the kidney.

and above it's not osmosis, it's diffusion.

參考: myself and heinemann biology textbook, heinemann biology textbook, heinemann biology textbook

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