09 Gep T5 Tpt In Man

Maris Stella High School GCE O Level Science Biology GEP: Topic 5

Name: ___________________ Class (Index No.): _____ ( ) Date: ________________

Transport in man Q.

Three different types of haemoglobin were extracted from a pregnant woman. The percentage saturation of haemoglobin with oxygen is a measure of how readily the haemoglobin binds with oxygen. Table 1 shows the percentage saturation of haemoglobin at different partial pressure of oxygen. Table 1 Partial Pressure of oxygen / Kpa % saturation of myoglobin % saturation of fetal haemoglobin % saturation of normal haemoglobin

(a)

0 0 0 0

2 60 20 12

4 84 56 36

6 94 80 66

8 96 90 82

10 98 94 90

12 98 98 96

14 98 98 98

Using the data given in Table 1, plot the percentage saturation of the three types of haemoglobin 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 oxygen temporarily and supplies muscle cells with oxygen. Suggest why myoglobin binds to oxygen differently from normal haemoglobin when the partial pressure of oxygen is low. [2] __________________________________________________________________ __________________________________________________________________ __________________________________________________________________ ___________________________________________________________________

(c)

Fetal haemoglobin was extracted from the pregnant woman’s fetus during pregnancy. i.

Describe how the fetus obtains oxygen from the mother during the development of the fetus. [3] _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ __________________________________________________________________

ii.

With reference to the data, explain whether the fetal haemoglobin is well-adapted for its function. [2] ________________________________________________________________ ________________________________________________________________ ________________________________________________________________

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Answers 6 (a)

The graph should look like this:

All point plotted correctly; best fit curve for myoglobin All point plotted correctly;best fit curve for fetal haemoglobin All point plotted correctly;best fit curve for normal haemoglobin *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)

(c)

(i)

Myoglobin combines more readily with oxygen than normal haemoglobin at low partial pressure of oxygen to ensure that the muscle cells receive sufficient oxygen for respiration during muscle contraction. The fetal blood capillaries are separated from the mother’s blood by maternal blood spaces / a thin layer of tissue in the placenta. Oxygen from the mother’s blood diffuses into the blood spaces / layer of tissue and then into the fetal’s blood. Reference to diffusion gradient

(ii) The fetal haemoglobin binds more readily to oxygen than normal haemoglobin so that it can take in as much oxygen as possible from the maternal blood spaces / layer of tissue

[1] [1] [1]

[1] [1]

[1] [1] [1] [1] [1]

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