regulation of blood water potential

Question 1

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of
both men and women. Affected individuals have proteinuria (high quantities of
protein in their urine).
(a)
(b)
Q2.
(a)
Suggest how AS could cause proteinuria. (2)

Answer 1

damages basement membrane
proteins can pass into filtrate

Question 2

Describe how ultrafiltration occurs in a glomerulus. (3)

Answer 2

-high hydrostatic pressure
-water, glucose, amino acids forced out of
-gaps in endothilial cells
-gaps in basement membrane

Question 3

Scientists investigated the relationship between the thickness of the kidney
medulla of different species of mammals and the concentration of their
urine.
The graph shows their results.
Explain the pattern shown by the results in the graph above. (3)

Answer 3

thicker medulla- longer loop of henle
increase in sodium ion concentration
Water potential gradient maintained so more water reabsorbed.

Question 4

Furosemide and CVT are drugs used to remove excess fluid from the body.
Scientists investigated the effect of these drugs on the volume of urine produced
by human volunteers. The scientists used the following method.
* They divided volunteers into three groups, A, B and C at random.
* They gave all the volunteers the same food for 3 days.
* After 3 days, they gave the volunteers in group A a tablet containing
furosemide, the volunteers in group B a tablet containing CVT and the
volunteers in group C a placebo (a tablet that did not contain either drug).
* They then found the mean volume of urine produced by each group in the
4 hours after taking the tablets.
Some of the results the scientists obtained are shown in Table 1.
A value of ± 2 standard deviations from the mean includes over 95% of the data.
Table 1
Group
Mean volume of urine
produced in 4 hours /
cm3 (± 2 standard
deviations)
A
(furosemide)
B
(CVT)
1980
(± 152)
1201
(± 119)
C
(placebo)
(a)
312
(± 57)
All the volunteers were given the same food for 3 days.
Suggest and explain one reason why they were given the same food. (2)

Answer 4

affects water potential
affects volume of urine

Question 5

Furosemide is sometimes used to treat high blood pressure.
Suggest how furosemide would cause a decrease in blood pressure (1)

Answer 5

lower volume of blood

Question 6

Furosemide inhibits the absorption of sodium and chloride ions from the
filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine
produced.

Question 7

Furosemide inhibits the absorption of sodium and chloride ions from the
filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine
produced. (3)

Answer 7

water potential of filtrate decreased
less water reabsorbed via osmosis
collecting duct is where osmosis occurs

Question 8

When a person is dehydrated, the cell volume of an osmoreceptor
decreases.
Explain why. (2)

Answer 8

blood water potential is lower
water moves from osmoreceptor to blood via osmosis.

Question 9

Stimulation of osmoreceptors can lead to secretion of the hormone ADH.
Describe and explain how the secretion of ADH affects urine produced by
the kidneys. (4)

Answer 9

increased permeability of cells
more water reabsorbed via osmosis from collecting duct
lower volume of urine
urine more concentrated

Question 10

Creatinine is a breakdown product of creatine found in muscle tissues.
Apart from age and gender, give two factors that could affect the
concentration of creatinine in the blood. (2)

Answer 10

ethnicity
exercise