Biology

asal · March 6, 2011

can you please help in in the following questions plz

Please attach list of references at end of assignment.

1. 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 Bowman’s (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 Henlé, ions are actively pumped out of

the nephron. This causes..................................................to be drawn out of the collecting duct.

(Total 6 marks)

2. 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-³

Concentration of substance / g dm–3

Substance

Bowman’s

capsule

Proximal

convoluted

tubule

Distal

convoluted

tubule

Collecting

duct

Urea

0.3

0.55

6

15

Glucose

0.1

0

Sodium ions

0.33

0.1

0.33

Potassium ions

0.17

0.02

0.06

0.85

(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)

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

(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.

(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)

(Total 13 marks)

3 . 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.

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

...………………………………………………………………………………

(3)

(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 Henlé assist in water reabsorption from the filtrate back into the body.

...…………………………………………………………………………………....

..…………………………………………………………………………………….

(2)

(Total 8 marks)

4. The diagram below shows the human respiratory system.

Fig 1. The Human Respiratory System

Complete the ten missing labels by filling in the correct names for the parts in the table below:-

Number

Name

Number

Name

1

6

2

7

3

8

4

9

5

10

(Total 5 marks)

5. The diagram below shows a spirometer, which can be used to measure lung volumes in humans.

(a) State the purpose of the soda lime in the spirometer.

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

(1)

(b) Describe how you would use a spirometer to measure a person’s vital capacity.

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

(4)

©. Diagram A and diagram B below show recordings of the breathing patterns of a person.

In diagram A the person is at rest. In diagram B the person has just finished a period of strenuous exercise.

(i) Calculate the mean tidal volume between 10 and 30 seconds when the person is at rest. Show your working.

Answer .................................

(2)

(ii) The ventilation rate of a person can be calculated by multiplying the rate of breathing by the depth of breathing. Use diagram B to calculate the ventilation rate of the person during the first 10 seconds after exercise. Show your working.

Answer .................................

(2)

(iii) Using the data in the recordings, compare the breathing patterns of this person before and after exercise.

……………………………………………….………………………………………

………………………………………………………………………………………..

(3)

(Total 12 marks)

Level

TASK 1

Please attach list of references at end of assignment.

1. Read the following passage about hormones involved in the regulation of blood glucose levels, then write on the dotted lines the most appropriate word or words to complete the passage.

When blood glucose levels rise above normal …………………………….. is

released from the …………………………….. cells of the islets of Langerhans

in the …………………………… . This lowers the blood glucose levels by

increasing the uptake of glucose into cells and promotes the conversion of

glucose into …………………………….. . Other cells in the islets of Langerhans

secrete …………………………….. which raises the level of blood glucose.

(Total 5 marks)

2. Read through the following passage about heat stress, then write on the dotted lines the most appropriate word or words to complete the passage.

The temperature of the blood is controlled by the ........................………… in the

brain. As the environmental temperature rises, thermoregulatory mechanisms

cause an increase in sweating and an increase in ........................………… to the

skin. Heat is lost from the body when water in the sweat ………………………...

from the surface of the skin. If excessive sweating occurs, the body may suffer

from dehydration and from salt deprivation. This loss of sodium and chloride

ions in sweat can cause painful heat........................…………In extreme

situations, the core temperature of the body may rise. A life-threatening

condition occurs when the core temperature reaches the………………………….

temperature.

(Total 5 marks)

3. In an investigation, groups of cells from the islets of Langerhans were separated from some fresh pancreatic tissue. Each group of cells was kept in a bathing solution similar to blood plasma. Each solution contained a different concentration of glucose.

The quantity of insulin released from the cells after 1 minute was measured. The results of this investigation are shown in the graph below.

(a) Describe the effect on the release of insulin from the cells when the glucose concentration is increased above 2.5 mmol dm–3.

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

(2)

(b) Suggest what these results indicate about the way in which changes in blood glucose levels are detected.

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

(2)

© Suggest why there is no change in the release of insulin from the cells when the glucose concentration is below 2.5 mmol dm–3.

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

(1)

(d) The normal concentration of glucose in the blood is about 5.0 mmol dm–3. With reference to the graph, and to your own knowledge of how insulin functions, explain how a blood glucose concentration of 7.5 mmol dm–3 would be brought down to normal in the body of a mammal.

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

(3)

(e) Name two hormones, other than insulin, that affect blood glucose levels in mammals.

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

(2)

(Total 10 marks)

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4. The diagram below shows the essential components of a homeostatic control system which regulates body temperature.

(a) With reference to the diagram, explain what is meant by the term negative feedback.

……………………………………………………………………………………….

(3)

(b) With reference to the diagram, suggest how the hypothalamus coordinates the regulation of body temperature.

……………………………………………………………………………………….

(2)

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© Compare the mechanism by which blood glucose concentration is regulated with the control system shown in the diagram.

……………………………………………………………………………………….

(3)

(Total 8 marks)

5. (a) With the use of an example (e.g. fever or childbirth) explain what is meant by

positive feedback.

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