1.

Describe the following processes which occur during urine formation in mammals. (a) Ultrafiltration .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(b)

Selective reabsorption of glucose .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2) (Total 4 marks)

2.

The diagram below shows the simplified structure of a kidney tubule (nephron).

(a)

In the table below, columns 1 and 2 show the quantities of water, glucose and urea passing through P and Q in a 24 hour period. Column 3 and 4 show the quantities and percentages reabsorbed during the same period. Complete the table by writing the correct figures in the boxes labelled (i) to (iv). Q u a n tity p a s s in g th ro u g h P 180 dm 180 g 53 g(ii) (iii)

S u b s ta n c e W a te r G lu c o s e U re a

Q u a n tity p a s s in g th ro u g h Q 1 .5 d m

Q u a n tity re a b so rb e d 1 7 8 .5 d m 180 g(i)

P e rc e n ta g e re a b so rb e d

100(iv )

25 g

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(4)

(b)

Describe how R is involved in adjusting the concentration of the filtrate as it passes through the medulla of the kidney. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(3) (Total 7 marks)

3.

The graph below shows how the rates of filtration and reabsorption of glucose in human nephrons vary with concentration of glucose in the blood plasma. 4

3 R a te o f filtra tio n o r re a b s o rp tio n o f g lu c o s e 2 / m m o l m in 1 K ey F iltra tio n ra te R e a b s o rp tio n ra te

1

0

0

10

20

30

40

C o n c e n tra tio n o f g lu c o s e in b lo o d p la s m a / m m o l d m 3 (a) (i) From the graph determine the maximum rate of glucose reabsorption.(1)

..........................................................................................................................

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(ii)

Comment on the relationship between filtration rate and reabsorption rate as shown by these two curves. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(3)

(b)

If the concentration of glucose in the blood plasma exceeds 20 mmol dm3, glucose appears in the urine. Suggest an explanation for this observation. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(c)

(i)

State where in the nephron glucose is reabsorbed.(1)

.......................................................................................................................... (ii) Describe how glucose is reabsorbed. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(2)

(iii)

Name two other substances which are reabsorbed in the same part of the nephron as glucose. 1 ..................................................................................................................... 2 .....................................................................................................................(2) (Total 11 mark)

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4.

Diabetes insipidus is a condition in which large volumes of dilute urine are produced. The volume of urine produced each day by a patient with diabetes insipidus was recorded. On certain days the patient received an injection of pituitary extract. The results are shown in the table below. The asterisks (*) indicate the days on which pituitary extract was injected. D ay 1 2 3 4 5 6 7* 8 (a) V o lu m e o f u rin e /d m 5 .4 6 .0 5 .8 5 .0 7 .0 5 .7 1 .9 2 .23

D ay 9 10 11 12 13* 14* 15* 16*

V o lu m e o f u rin e /d m 6 .3 4 .9 5 .1 5 .5 1 .5 2 .1 2 .4 1 .7

3

Describe the effect of the injection of pituitary extract on the volume of urine produced each day. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2)

(b)

Name the substance responsible for this effect. ....................................................................................................................................(1)

(c)

Describe how this effect is brought about. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... ....................................................................................................................................(2) (Total 5 marks)

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5.

Read through the following account of kidney function, then write on the dotted lines the most appropriate word or words to complete the account. In the kidney, the renal artery branches to form many smaller arterioles, each of which divides further to form a knot of capillaries called a ............................................... Here, small molecules such as..................................and ................................................are forced into the cavity of the Bowmans (renal) capsule by process of....................................................Selective reabsorption takes place in the nephron. In the proximal convoluted tubule all the....................................................is reabsorbed. In the ascending limb of the loop of Henl, ions are actively pumped out of the nephron. This causes..................................................to be drawn out of the collecting duct.(Total 6 marks)

6.

An investigation was carried out into the reabsorption of water from the nephrons in human kidneys. The total volume of filtrate produced by the glomeruli in the kidneys was 180 dm3 per day. The table below shows the volumes of water which were reabsorbed from this filtrate in different regions of the nephrons. Volume of water reabsorbed / dm3 per day 147.0 10.0 19.2 to 19.5 2.2 to 2.7

Region of nephrons

Proximal convoluted tubules Loops of Henl Distal convoluted tubules Collecting ducts (a)

Calculate the maximum volume of urine produced per day. Show your working.

Answer .(2)

(b)jumeirah college

(i)

Describe how water is reabsorbed from the proximal convoluted5

tubule. ... ... ... ... ... ...(3)

(ii)

Explain why the volume of water reabsorbed in the distal convoluted tubules and collecting ducts is variable. ... ... ... ... ... ...(3)

(c)

Explain how the nephrons of desert mammals are adapted to increase conservation of water. .. .. .. .. .. ..(3) (Total 11 marks)

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7.

An investigation was carried out into the reabsorption of water from the nephrons in human kidneys. The total volume of filtrate produced by the glomeruli in the kidneys was 180 dm3 per day. The table below shows the volumes of water which were reabsorbed from this filtrate in different regions of the nephrons. Volume of water reabsorbed / dm3 per day 147.0 10.0 19.2 to 19.5 2.2 to 2.7

Region of nephrons

Proximal convoluted tubules Loops of Henl Distal convoluted tubules Collecting ducts (a)

Calculate the maximum volume of urine produced per day. Show your working.

Answer .(2)

(b)

(i) tubule.

Describe how water is reabsorbed from the proximal convoluted

... ... ... ... ... ...(3)

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(ii)

Explain why the volume of water reabsorbed in the distal convoluted tubules and collecting ducts is variable. ... ... ... ... ... ...(3) (Total 8 marks)

8.

An investigation was carried out into the rate of urine production in normal human subjects. Ten people fasted overnight, then, at 8.00 a.m., emptied their bladders. Five subjects then each drank 1 dm3 of water, while the other five (the control group) drank nothing. All ten then remained at rest and emptied their bladders every half an hour for 2.5 hours. The mean volume of urine produced every half hour, by each of the two groups, was recorded.

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The results are shown in the graph below. 300 280 260 240 220 200 V o lu m e o f 1 8 0 u rin e / c m 3 160 140 120 100 80 60 40 20 0 0 (a) 30 60 90 120 150 T im e / m in Describe the results obtained for the control group. . . . .(2)

K EY D ra n k 1 d m o f w a te r C o n tr o l

3

(b)

Compare the results for the group who drank water with those for the control group. . . . .(2)

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(c)

Explain the changes in the volumes of urine produced by the group who drank water, over the time period from 30 to 90 minutes. . . . . . . . .(4)

(d)

Suggest how the results for this group might have differed if they had taken exercise during the experiment. Explain your answer. . . . . . .(3) (Total 11 marks)

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9.

The diagrams below are from different regions of a mammalian kidney and show transverse sections of proximal convoluted tubules, distal convoluted tubules and loops of Henl.

(a)

Identify the region of the kidney shown in diagram A, giving a reason for your answer. . . . .(2)

(b)

(i) The tissue was stained during the preparation of the sections. The cells of the proximal convoluted tubules stained more densely than those of the distal convoluted tubules because they contained a greater density of organelles. Explain this difference in density of organelles in terms of the functions of the proximal convoluted tubule. ... ... ... ... ... ...(3)

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(ii)

State two ways, shown in the diagrams and other than the dense staining of the cytoplasm of the cells, in which the proximal convoluted tubules differ from the distal convoluted tubules. 1 ... ... 2 ... ...(2)

(c)

(i)

State the function of the loop of Henl.

... ...(1)

(ii)

Describe the role of the descending limb of the loop of Henl. ... ... ... ...(2) (Total 10 marks)

10.

An investigation was carried out to determine the quantities of water, glucose and urea passing through different parts of kidney nephrons in 24 hours. The results are shown in the table below. Substance Quantity passing through Bowmans capsules 190 dm3 180 g 53 g Quantity passing through collecting ducts 1.5 dm3 0.0 g 25 g 100 52.8 Percentage reabsorbed

Water Glucose Urea

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(a)

Calculate the percentage reabsorption of water. Show your working.

Answer ....................................................................(2)

(b)

Explain how each of the following substances is reabsorbed from the proximal convoluted tubule of the nephron. (i) glucose ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................(3)

(ii)

water ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................(3)

(c)

Suggest a reason why some urea is reabsorbed by the nephron. ................................................................................................................................. ................................................................................................................................. ................................................................................................................................. .................................................................................................................................(2) (Total 10 marks)

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11.

An investigation was carried out into the excretion of urea in the urine of a healthy student on a high and low protein diet. The results for each diet are shown in the table below. The results are mean values for the second, third and fourth days after starting the diet. Diet High protein Low protein (a) Protein intake/g per day 189 56 Daily output of urea /g 21.4 8.5

Calculate the percentage decrease in the daily output of urea between the two diets. Show your working.

Answer....................................................................(2)

(b)

Give an explanation for this difference in the daily output of urea. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(3)

(c)

Suggest why many aquatic organisms excrete ammonia, rather than urea, as the end product blank of protein metabolism. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(2) (Total 7 marks)

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12.

The diagram below represents a kidney tubule (nephron). A

B D

C

(a)

Name the parts labelled A, B, C and D. A ................................................................................................................................. B ................................................................................................................................. C ................................................................................................................................. D .................................................................................................................................(2)

(b)

The concentration of urea was measured in the parts of the nephron labelled A, B and D. Part of nephron A B D Concentration of urea / g dm3 0.30 0.55 6.0-7.0

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(i)

Explain how the change in the urea concentration between part A and part B is brought about. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................(2)

(ii)

Explain why the urea concentration in part D of the nephron may vary at different times during the day. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................(3)

(c)

When this person ate a high protein diet, the urea concentration in part A of the nephron was 0.36 g dm3. (i) Calculate the percentage change in the urea concentration in part A resulting from this change in diet.

Answer..............................................(3)

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(ii)

Give an explanation for this change in urea concentration. ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................(3) (Total 13 marks)

13.

An experiment was carried out to investigate the effect of salt intake on the volume of urine excreted. Three male volunteers were kept on a salt free diet for two weeks. Their kidney function was then tested by asking each to drink one litre of water and then measuring the volume of urine produced every 20 minutes. This experiment was then repeated with the same volunteers after they had eaten a diet having normal salt levels for a further two weeks. An extract from the investigators notebook showing the results of this experiment is given below.

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(a)

Tabulate these data, organising them in a suitable way so that the effect of the different diets on urine production can be compared.(4)

(b)

Use your tabulated results to draw a graph to compare the effect of the different diets on urine production.(4)

(c) (d)

Give two conclusions that you could draw from the results of this investigation.(2)

Suggest two ways in which this investigation could be modified to produce more reliable results.(2) (Total 12 marks)

14.

The diagram below shows the simplified structure of a kidney tubule (nephron).

P

A s c e n d in g lim b o f th e lo o p o f H e n l

Q

(a)

The table below shows the quantities of water and urea passing through P and Q in a period of 24 hours. The table also shows the quantities and percentages reabsorbed during the same period. Complete the table by writing the correct figures in the boxes labelled (i), (ii), (iii) and (iv). Substances Water Urea Glucose Quantity passing through P 180 dm 53 g 180 g (iv) Quantity passing through Q 1.5 dm 25 g (ii) 180 g Quantity reabsorbed 178.5 dm (i) (iii) 100(4)

Percentage reabsorbed

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(b)

Describe how the ascending limb of the loop of Henl is involved in adjusting the concentration of the filtrate as it passes through the medulla in the kidney. .. .. .. .. .. .. .. ..(4) (Total 8 marks)

15.

(a) The formation of the mammalian excretory product urea can be summarised by the following word equation. Ammonia + Carbon dioxide Urea + Water (i) Name the organ in which urea is formed. ..........................................................................................................................(1)

(ii)

State how the ammonia is produced. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(2)

(iii)

Suggest how the carbon dioxide used in the formation of urea is produced. .......................................................................................................................... ..........................................................................................................................(1)

(b)

In an investigation, a student compared the concentration of urea in her urine before and after taking a drink of water. The student measured the concentration of urea in urine samples for a period of 5 days. Each day she took a urine sample within 15 minutes of waking after a nights sleep. She then drank 0.75 dm3 water. A second urine sample was then taken 30 minutes after drinking the water.

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The results of this investigation are shown in the table. Urea concentration before drinking / mol dm3 1.1 1.3 1.1 1.0 1.5 1.2 Urea concentration after drinking / mol dm3 0.2 0.3 0.3 0.1 0.3 0.2

Day 1 2 3 4 5 Mean (i)

Calculate the mean percentage change in the urea concentration as a result of taking the drink of water. Show your working.

Answer ..............................................................(2)

(ii)

Explain how drinking the water may have caused the reduction in urea concentration in the urine. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(4)

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(iii)

Suggest why an estimate of the urea concentration in urine is not a reliable estimate of the total solute concentration of the urine. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... ..........................................................................................................................(2) (Total 12 marks)

16.

The diagram shows part of a nephron from a mammalian kidney. B lo o d e n te r in g v ia a ffe re n t a rte rio le

G lo m e ru lu s

C a v ity o f re n a l ( B o w m a n 's ) c a p s u le

B lo o d le a v in g v ia e ffe re n t a rte rio le

F iltr a te p a s s in g to re s t o f n e p h ro n (a) Name the region of the kidney in which the renal capsules are found. .(1)

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(b)

Describe and explain the process of ultrafiltration. . . . . . . . .(4)

(c)

Name one substance, filtered from the blood, that would be completely reabsorbed as the filtrate passes through the nephron. .(1) (Total 6 marks)

17.

The diagram below represents a kidney tubule (nephron).

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(a)

Name the regions labelled A, B and C. A .. B .. C ..(1)

(b)

In an investigation on a person eating a balanced diet, the concentration of urea over a 24 hour period was measured in the nephron regions A, B and C. The mean values of the urea concentrations are shown in the graph below. 7 .0 M ean 6 .0 c o n c e n tra tio n o f u re a 5 .0 / g d m 3 4 .0 3 .0 2 .0 1 .0 0 A B R e g io n o f n e p h ro n C

Explain how the change in urea concentration between parts A and B of the nephron is brought about. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ........................................................................................................................................(2)

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(c)

Although the urea concentration in regions A and B remained relatively constant 3 throughout the time period, the concentration in region C varied between 6 and 7 g dm . Suggest an explanation for this variation. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(3)

(d)

In a similar investigation, the person ate high protein meals during the 24 hour period. The urea concentration in region A of the nephron was found to have increased from 0.30 to 3 0.38 g dm . Give an explanation for the increase in urea concentration. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(4) (Total 10 marks)

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18.

The cell surface membrane is a barrier which prevents foreign material entering the cell and vital molecules and organelles from leaving. All cell membranes have some limited permeability to water, but the epithelial cells lining parts of the kidney nephrons have membrane water permeabilities many times greater than the normal level. This is due to the presence of specific membrane proteins, known as aquaporins, which only allow the passage of water molecules. (a) Explain why fatty acids and cholesterol, oxygen and carbon dioxide all diffuse freely through the cell surface membrane, but polar molecules and ions, such as sodium, do not. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(3)

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(b)

The graph below shows the permeability to water of different parts of the nephron. 10 000

P e rm e a b ility to w a te r / a rb itra ry u n its (lo g s c a le ) 1000

H ig h A D H

100 Low A D H 10

P ro x im a l c o n v o lu te d tu b u le

D e s c e n d in g lim b

A s c e n d in g lim b

D is ta l c o n v o lu te d tu b u le

C o lle c tin g duct

Loop of Henl Part of nephron What can you conclude from the graph about the number of aquaporins in the proximal convoluted tubule compared with the number in the distal convoluted tubule? ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(2)

(c)

Reabsorption of water from the filtrate depends on a water potential gradient between the filtrate and the blood. Explain how a water potential gradient is created in the proximal convoluted tubule. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(2)

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(d)

Using the information in the graph, and your own knowledge, explain how the loop of Henl enables the kidney to produce concentrated urine. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(5)

(e)

Describe and suggest an explanation for the effect of antidiuretic hormone (ADH) on the membrane permeability of the cells of the collecting duct, as shown on the graph. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(3) (Total 15 marks)

19.

The table below shows the typical concentration of four solutes (urea, glucose, sodium ions and potassium ions) in the filtrate produced in the Bowmans capsule and in the proximal convoluted tubule of a nephron (kidney tubule). Concentration of solute / g dm Solute Bowmans capsule Urea Glucose Sodium ions Potassium ions 0.30 0.10 0.33 0.173

Proximal convoluted tubule 0.55 0.00 0.33 0.0227

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(a)

Explain how the filtrate is produced in the Bowmans capsule. (3)

(b)

In the proximal convoluted tubule, large volumes of water are reabsorbed from the filtrate into the blood. Suggest why the concentration of sodium ions remains unchanged but the concentration of urea increases in the proximal convoluted tubule. (3)

(c)

The concentration of glucose decreases to zero in the proximal convoluted tubule. Suggest why it is necessary for complete glucose reabsorption to occur. (2) (Total 8 marks)

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20.

The graph below shows how the rates of filtration and reabsorption of glucose in human nephrons vary with the concentration of glucose in the blood plasma. 4 F iltra tio n ra te

3 R a te o f filtra tio n o r re a b s o rp tio n o f g lu c o s e 2 / m m o l m in 1

R e a b s o rp tio n ra te

1

0

0

10

20 30 C o n c e n tra tio n o f g lu c o s e in b lo o d p la s m a / m m o l d m

403

(a)

Name the region of the nephron where glucose is filtered and the region where it is reabsorbed. Region of glucose filtration .......................................................................................... Region of glucose reabsorption ....................................................................................(2)

(b)

Name one other substance which is reabsorbed in the same part of the nephron as glucose. ......................................................................................................................................(1)

(c)

With reference to the graph, describe the relationship between filtration rate and reabsorption rate as the concentration of glucose in the blood plasma increases. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3)

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(d)

Using the information in the graph, explain why glucose appears in the urine when the 3 plasma glucose concentration exceeds 10 mmol per dm . ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

(e)

Suggest why the presence of glucose in the urine results in the production of a larger volume of urine than when glucose is not present. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3) (Total 11 marks)

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21.

An investigation was carried out into the effect of antidiuretic hormone (ADH) on urine production in a mammal. The rate of urine production was measured over a period of 30 minutes. Five minutes after measurements began, ADH was injected into a vein of the mammal. The results are shown in the graph below. In je c tio n o f A D H 5

R a te o f u rin e 4 p ro d u c tio n / c m 3 m in 1 3

2

1

0

0

5

10

15

20

25 30 T im e / m in

(a)

Name the gland that releases ADH. ......................................................................................................................................(1)

(b)

Describe the effect of the injection of ADH on the rate of urine production in the mammal in this investigation. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(3)

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(c)

Describe the mechanism by which ADH produces the effect seen in this investigation. ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................(4)

(d)

In a similar investigation, an injection of sodium chloride (salt) solution was given after five minutes instead of ADH. This injection was observed to affect urine production in a similar way to ADH. Suggest how the sodium chloride brought about this effect. ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................(3) (Total 11 marks)

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22.

The table below shows the average concentrations of four substances, urea, glucose, sodium ions and potassium ions, in different regions of the kidney tubule (nephron). The figures are expressed as g dm Concentration of substance / g dm3 Substance Bowmans capsule 0.3 0.1 0.33 0.17 Proximal convoluted tubule 0.55 0 0.33 0.02 Distal convoluted tubule 6 0 0.1 0.06 Collecting duct 15 0 0.33 0.85

Urea Glucose Sodium ions Potassium ions (a)

Large volumes of water are reabsorbed into the blood from the proximal convoluted tubule. Suggest why the concentration of sodium ions remains unchanged but the concentration of urea increases.(2)

(b)

(i) Calculate the percentage change in the concentration of urea between the beginning and the end of the tubule. Show your working.(2)

(ii)

Suggest a reason for the change in the concentration of urea in the distal convoluted tubule and the collecting duct.(1)

(c)

Comment on the changes in the concentration of sodium ions and potassium ions in the distal convoluted tubule and collecting duct.(2)

(d)

The concentration of glucose falls to 0 in the proximal convoluted tubule. Explain how this is brought about.(2)

(e)

The diagram below shows a section through a cell wall of the proximal convoluted tubule of a kidney nephron.

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(i)

Name the features X and Y on the diagram of the cell from the proximal convoluted tubule and indicate their significance in the process you described in (d). X .. Significance .(2)

Y ... Significance ..(2)

(ii)

Name two structures other than those labelled X and Y which indicate that this is a eukaryotic cell. 1 2 (2) (Total 15 marks)

23.

An investigation was carried out into the water balance of the body in different situations. A record was kept of the water intake and water output of a student on three separate days: a normal day spent indoors in warm temperatures, a day spent outside in cold weather and a day during which the student ran a cross-country race. On each day, the total water uptake by the body was the same as the water output. The results are shown in the table below. Water source Uptake / cm3 In drinks In food Oxidation of food Total Output 1 cm3 Urine Sweat From lungs In faeces Total (a) Normal day 1500 800 300 2600 1100 1000 400 100 2600 Cold day 1500 800 300 2600 1500 600 400 100 2600 Day of race (i) .................... 1500 500 (ii).. 1200 3000 600 100 (iii) ..

Complete the table by calculating the volume of water uptake in drinks and the total water uptake and output for the day of the cross-country race. Write your answers on the lines labelled (i), (ii) and (iii) in the table.(2)

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(b)

(i) cold day.

Compare the water uptake and output on a normal day with that on a

.... .... .... .... ....(3)

(ii)

Describe and explain the difference in water output on the normal day and on the day of the race. .... .... .... .... ....(3)

(c)

(i)

Explain how the oxidation of food produces water in the body.

.... .... ....(2)

(ii)

Suggest why more water is produced by oxidation of food on the day of the race. .... .... ....(2)

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(d)

During the race, the secretion of adrenaline increases. Describe and explain one physiological effect that this increase in adrenaline would have on the student. .. .. ..(2) (Total 14 marks)

24.

The diagram below shows the loop of Henle from a nephron in the mammalian kidney. The numbers on the diagram show changes in the relative concentration of solutes in the filtrate as it passes through this part of the nephron. D ir e c tio n o f flo w o f filtr a te 100

300

D e s c e n d in g lim b 500 300

A s c e n d in g lim b

900

700

1200 (a) (i) Explain how, in the ascending limb, the relative concentration of solutes in the filtrate changes from 700 to 100. ... ... ... ...(3)

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(ii)

Explain how, in the descending limb and the base of the loop, the relative concentration changes from 300 to 1200. ... ... ... ...(3)

(b)

The ability of the nephron to reabsorb water from the filtrate is important in maintaining the water balance of the body. Describe how the concentration changes in the loop of Henl assist in water reabsorption from the filtrate back into the body. ....... ....... ....... .......(2) (Total 8 marks)

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37