- The formation of red precipitate indicates the presence of reducing sugar (glucose) in the water 1
this shows that the dialysis tubing is permeable to glucose permits the diffusion of glucose into the external solution 1
- Increased amount of precipitate in set-up B indicates the presence of more reducing sugar 1
which comes from the hydrolysis / break sown of starch 1
catalysed by the amylase / enzyme in digestive juice X 1
- * saliva / salivary juice 1
* pancreatic juice 1
the knot of the dialysis tubing should be tied tightly 1
the outside of the dialysis tubing should be rinsed with distilled water before immersing into the water 1
any one of the following:
– after putting in the dialysis tubing, the water in the
boiling tube should be tested for the presence of
reducing sugar immediately
– the digestive juice X should be tested for the
presence of reducing sugar any one 1
– the dialysis tubing should be examined for any
damage
– the volume of distilled water in the boiling tube
should be the same
the difference in no. of yeast cells between flasks A and B at hour 20
= 675 – 150 1
= 525 1
in flask A, the yeast cells undergo aerobic respiration whereas in flask B,
the yeast cells undergo anaerobic respiration 1
anaerobic respiration releases less energy 1
for cell division / growth of the yeast 1
OR
in flask A, the yeast cells undergo aerobic respiration whereas in flask B, the yeast cells undergo anaerobic respiration 1
anaerobic respiration produces ethanol / alcohol 1
which inhibits the cell division / growth of the yeast 1
the rate of reproduction of the yeast at hour 8 is much faster than that at
hour 16 1
reasons: +
– at hour 16, nutrients in the solution may become exhausted 1
– at hour 16, there may be accumulation of toxic wastes 1
both cause a decline in the reproductive rate of yeast
No mark for the whole set-up if it is not workable
(e.g. using dry yeast, with an oil layer)
insulating layer and stopper 1
thermometer (the bulb must be immersed in the mixture) 1
correct connection of tubes 1
clear, well-labelled and accurate diagram (D) 1
Total:12 marks
the movement of the train results in the movement of the endolymph / the gelatinous structure of the semi-circular canal 1
in the direction opposite to that of the train movement 1
this stimulates the sensory hair cells and 1
nerve impulses are generated 1
impulses then travel to the cerebrum 1
where the sensation of the direction of movement is produced
- cornea transplant 1
- this treatment requires the donation of cornea from other people 1
very few people are willing to do this after death 1
Total: 8 marks
the starch in the rice is first digested into glucose and 1
absorbed into the blood of the small intestine 1
- liver 1
glycogen is broken down into glucose which is then released into the
blood 1
- this provides more glucose for the respiration of muscle 1
to release more energy for muscle contraction during exercise 1
from hour 0.5 to 1.5, the increase in blood glucose level 1
stimulates the pancreas 1
to secrete more insulin 1
the increased insulin lowers the blood glucose level 1
from hour 1.5 to 3, a decrease in the blood glucose cause the pancreas to
secrete less insulin 1
Total: 11 marks
it allows the mesophyll cells (photosynthetic cells) 1
to have a rapid supply gases, and 1
adequate supply of light 1
because mesophyll cells contain chloroplasts / chlorophyll 1
to absorb sunlight 1
carbon dioxide is used in photosynthesis 1
carbon dioxide is released in respiration 1
since the rate of photosynthesis is faster than the rate of respiration at
daytime 1
carbon dioxide has to taken into the leaf from the air
during daytime, stomata open in the presence of light 1
temperature of air is higher / the relative humidity of air is lower / the rate
of evaporation is faster 1
water vapour diffuses faster / diffuses along a steeper concentration gradient
through the stomatal pore 1
Total: 11 marks
the high temperature is due to the breakdown / decay of organic wastes 1
by respiration / activities of microorganisms 1
which release heat 1
as fertilizer for plant growth 1
– it causes less pollution to the environment
– it reduces the consumption of fossil fuels / chemical
fertilizers any TWO 1, 1
– the wastes can be recycled into useful matters
e.g. fertilizer, fuel
– land in Hong Kong is too expensive / not enough for
building such pit
– it is smelly in a crowded area
– there are problems of collection and transport for any TWO 1, 1
wastes
– energy production by this practice cannot meet the
great demand in Hong Kong
and other acceptable suggestions
Total: 8 marks
oxygen 1
glucose / amino acids / mineral salts / vitamins / water 1
with a rich supply of blood capillaries,
substances absorbed can be transported away 1
so as to maintain a steep concentration gradient across the wall of the air
sacs / villus 1
the capillary network provides a large surface area 1
as a result, the rate of diffusion of substance increase 1
A ®
* pulmonary vein ®
* left atrium (auricle) ®
* left ventricle ®
* aorta ®
B 1/2 ´
4
The blood carbon dioxide content increases 1
because carbon dioxide is produced by respiration 1
by the cells in the villus (small intestine) 1
Total: 11 marks
Title (T) 1/2
correct choice of axes (A) 1/2
correct labelling of axes with units (L) 1
correct plotting and joining of all points (P) 1
The potato strip decreased in length 1
this indicates that the potato cells were at a higher water potential than the
sugar solution 1
water moved out of the potato cells 1
the potato cells shrank in size / cells became less turgid 1
- Hour 2.5 to 3 1
(if the starting time lies between hour 2 – 2.5; must refer to the graph plotted)
- It is because the water potential of potato cells became equal to that of
the sugar solution 1
there was no net water movement in and out of the cells 1
(accept: no osmosis or no diffusion)
Total: 10 marks
(4) ®
(2) ®
(3) ®
(1) 2 or 0
- DNA content of cell (2) is only half of that in cell (4) 1
- Chromosomes of cell (4) will separate into 2 equal groups, 1
resulting in the formation of two daughter cells (cell (1)) 1
since chromosomes are made of DNA, the process will reduce the DNA
content of cell (1) to half of that of cell (4) 1
DNA controls the formation of proteins 1
such as enzyme 1
which catalyse chemical reactions in the cells 1
Total: 9 marks
Discontinuous variation 1
as the character (seed colour) can be grouped into a few distinct classes 1
Environmental facters:
– light supply
– carbon dioxide supply any one 1
– water supply
– nutrients supply
- genetic variation may be caused by:
– random fertilization 1
– independent assortment of chromosomes in meiosis 1
the ratio of the number of yellow seeds to green seeds among the offspring is 143 : 46 1
which is approximately 3 : 1 1
according to the Mendel’s Law, the parent is thus heterozygous for the seed colour 1
the parent plant, which germinated from a yellow seed, should contain alleles for yellow seed 1
it produces some green seeds from the parent 1
therefore the parent plant is heterozygous for the seed colour 1
- mutation is a sudden and inheritable change of genetic material (gene / chromosome) 1
- anther / pollen grain / ovary / ovule 1
Total: 10 marks
through placents (structures A), nutients diffuse from the 1
maternal blood into the foetal blood and carried by the
umbilical cord to the foetus 1
* amniotic fluid 1
– act as shock absorber / to protect the
foetus from mechanical damage
– prevent desiccation of the foetus
– maintain a relatively constant any two 1, 1
environment around the foetus
– allow the foetus to move freely /
support the foetus inside the uterus
A will be expelled out of the woman’s body 1
by the contraction of the uterus 1
Milk is rich in protein which is important for 1+
the growth of the foetus 1
milk is rich in vitamin D / calcium which is important for the 1+
development of bones and teeth of the foetus 1
Total: 12 marks
It is taken from the root 1+
Reason: xylem / vascular tissue is found at the centre of the section 1
- The cell wall of cell type A is thicker than that of cell type B 1
The thick cell wall is rigid / hard 1
– to provide support to the plant
– to give better penetrating power through the soil any 2 1, 1
– to prevent it from collapse
– to increase the tensile strength of the root
the dark blue colour indicates the ptesence of starch 1
cell type B is for food storage 1
Total: 8 marks