CE BIO 1990 Alex Lam 1. (a) (i) cells A and D -----------------------------------------------1 or 0 possession of cell wall, -----------------------------------------1 and large / central vacuole / peripheral nucleus -----------------1 (1) cell A is for regulating the size of the stomatal opening / provides a passage for gases / water vapour --------1 cell B is for transmitting nerve impulses / message / information ------------------------------------------------------1 (2) cell A - thicker inner wall and thinner wall / kidney-shaped - 1 cell B - long cellular extension / nerve fibre / branched endings ----------------------------------------------------------1 (ii) cell C bursts / swells ---------------------------------------1 cell D becomes turgid / shows no change --------------------------1 water potential of distilled water is greater than that of the cells (C and D) --------------------------------------------------------1 water enters the cells by osmosis --------------------------------1 cell C expands continuously until it bursts ----------------------1 but cell D does not burst because of the presence of the inelastic cell wall --------------------------------------------------------1 Total : 13 Marks 1. (a) (i)&(ii) Most candidates were able to answer the question correctly with reference to the features shown in the diagram. A small number of candidates, however, included features not shown in the diagram such as the presence of chloroplast in cell A or myelin sheath in cell B. This suggests they had answered by rote memory. Some candidates did not realise that vacuoles are present in both plant and animal cells, although the vacuoles in plant cells are usually larger and central in position. (iii) Many candidates could give a clear and accurate account of the changes in cells C and D using the concept of water potential. This shows that water potential is a useful concept in understanding and explaining osmosis in living cells. Paper I Marking Scheme & Year Report P.1
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CE BIO 1990 Alex Lam1. (a) (i) cells A and D -----------------------------------------------------------------------------------------------1 or 0
possession of cell wall, ----------------------------------------------------------------------------------------1
and large / central vacuole / peripheral nucleus ---------------------------------------------------------1
(1) cell A is for regulating the size of the stomatal
opening / provides a passage for gases / water vapour ----------------------------------------1
cell B is for transmitting nerve impulses / message / information ----------------------------1
(2) cell A - thicker inner wall and thinner wall / kidney-shaped ------------------------------------1
cell B - long cellular extension / nerve fibre / branched endings -----------------------------1
(ii) cell C bursts / swells -------------------------------------------------------------------------------------------1
cell D becomes turgid / shows no change ----------------------------------------------------------------1
water potential of distilled water is greater than that of the cells (C and D) ----------------------1
water enters the cells by osmosis --------------------------------------------------------------------------1
cell C expands continuously until it bursts ----------------------------------------------------------------1
but cell D does not burst because of the presence of the inelastic cell wall ----------------------1
Total : 13 Marks
1. (a) (i)&(ii) Most candidates were able to answer the question correctly with reference to the
features shown in the diagram. A small number of candidates, however, included
features not shown in the diagram such as the presence of chloroplast in cell A or
myelin sheath in cell B. This suggests they had answered by rote memory. Some
candidates did not realise that vacuoles are present in both plant and animal cells,
although the vacuoles in plant cells are usually larger and central in position.
(iii) Many candidates could give a clear and accurate account of the changes in cells C and D
using the concept of water potential. This shows that water potential is a useful concept in
understanding and explaining osmosis in living cells.
Paper I Marking Scheme & Year Report P.1
CE BIO 1990 Alex Lam1. (b) (i) from 2.0 s to 4.0 s -----------------------------------------------------------------------------------------------1
pressure in the lungs is greater than the atmospheric pressure ------------------------------------1
(ii) - intercostal muscles relax )
- to lower the ribs )
- diaphragm relaxes ) any THREE -----------------------------------------------------1,1,1
- to curve upward )
these actions decrease the volume of the thorax / increase
the air pressure of the lungs ---------------------------------------------------------------------------------1
(iii) 15 breaths per minute (no unit, no mark) ---------------------------------------------------------------1
(iv) showing a higher frequency ----------------------------------------------------------------------------------1
showing a greater magnitude---------------------------------------------------------------------------------1
(no unit/reference point, no mark)Total : 9 Marks
1. (b) (i) Quite a number of candidates stated wrongly that air moves out of the lungs when the
pressure in the lungs is increasing. They failed to see that air is breathed out only when the
lung pressure exceeds the atmospheric pressure.
(ii) This part was well answered, showing that the candidates were familiar with the mechanism
of breathing movements.
(iii) Some candidates did not express the rate of breathing as number of breaths per unit time.
(iv) Many candidates failed to provide a useful reference to indicate that the curve sketched
shows an increase in rate and depth of breathing during exercise in comparison with those
at rest.
Paper I Marking Scheme & Year Report P.2
CE BIO 1990 Alex Lam1. (c) (i) (1) yellow (18 2); purple (53 2) ---------------------------------------------------------------1 or 0
nerve impulses pass along the sensory neurone -------------------------------------------------------1
and via the relay neurone / assoication neurone / intermediate nueorne to the brain where the sensation of touch is produced ------------------------------------------------1
and then nerve impulses sent from the brain via the
motor neurone to the muscles responsible for speech ------------------------------------------------1