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Maris Stella High School Name: ___________________

GCE O Level Science Biology Class (Index No.): _____ ( )

GEP: Topic 5 Date: ________________

Transport in man

Q. Three different types of haemoglobin were extracted from a pregnant woman. Thepercentage saturation of haemoglobin with oxygen is a measure of how readily thehaemoglobin binds with oxygen.Table 1 shows the percentage saturation of haemoglobin at different partial pressure of

oxygen.

Table 1

Partial Pressure of oxygen / Kpa 0 2 4 6 8 10 12 14

% saturation ofmyoglobin 0 60 84 94 96 98 98 98

% saturation offetal haemoglobin0 20 56 80 90 94 98 98

% saturation ofnormalhaemoglobin 0 12 36 66 82 90 96 98

(a) Using the data given in Table 1, plot the percentage saturation of the three types ofhaemoglobin at different partial pressure of oxygen on the graph paper below. [3]

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(b) Myoglobin is a special type of haemoglobin found in muscle cells. It stores oxygentemporarily and supplies muscle cells with oxygen. Suggest why myoglobin binds tooxygen differently from normal haemoglobin when the partial pressure of oxygen is low.

[2]

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(c) Fetal haemoglobin was extracted from the pregnant womans fetus during pregnancy.

i. Describe how the fetus obtains oxygen from the mother during the development of thefetus. [3]

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ii. With reference to the data, explain whether the fetal haemoglobin is well-adapted for itsfunction. [2]

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Answers

6 (a) The graph should look like this:

All point plotted correctly; best fit curve for myoglobin [1]

All point plotted correctly;best fit curve for fetal haemoglobin [1]

All point plotted correctly;best fit curve for normal haemoglobin [1]

*Minus 1 mark for missing labels of x- and y-axes

*Minus 1 mark for missing labels for each curve

*Minimum mark: 0

(b) (i) Myoglobin combines more readily with oxygen than normal

haemoglobin at low partial pressure of oxygen

[1]

to ensure that the muscle cells receive sufficient oxygen for

respiration during muscle contraction.

[1]

(c) (i) The fetal blood capillaries are separated from the mothers blood

by maternal blood spaces / a thin layer of tissue in the placenta. [1]

Oxygen from the mothers blood diffuses into the blood spaces / layer

of tissue and then into the fetals blood.

[1]

Reference to diffusion gradient [1]

(ii) The fetal haemoglobin binds more readily to oxygen than normalhaemoglobin

[1]

so that it can take in as much oxygen as possible from the maternal

blood spaces / layer of tissue

[1]