New Senior Secondary Mastering Biology
Suggested answers to Exercise and Reading to learn
Chapter 5
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Suggested answers to Exercise and Reading to
learn
(Note: The overseas examination boards bear no responsibility for the suggested answers
contained in this publication. Answers for HKCEE and HKALE questions are not available due
to copyright restrictions.)
Ch 5 Food and humans
Exercise
Multiple-choice questions (p. 5-31)
1
5
D
D
2
6
D
D
3
7
A
D
4
B
Short questions (p. 5-32)
8
HKCEE Human Biology 2001 I Q4b
9
HKCEE Biology 2005 I Q6
10
Constituent of the diet
Description of one effect of deficiency
vitamin A
reduced ability to synthesize retinal pigments
vitamin C (ascorbic acid)
scurvy / bleeding from small blood vessels or
gums / poor wound healing
calcium
rickets / weak bones or teeth / bleeding /
decreased muscular activity
iron
reduced ability of the blood to carry oxygen
1m x 4
11
a
Bananas: 75.7
0.5m
Grapes: 84.7
0.5m
b
Fat
1m
c
Apple contains more carbohydrate / pears contain less carbohydrate.
1m
Apple contains less water / pears contain more water.
1m
Use several samples of each fruit / Repeat experiment
0.5m
Calculate average result
0.5m
d
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12
a
Chapter 5
p.2/5
i
B, because it is rich in vitamin A.
1m
ii
A, because it contains the largest amount of fats. (Though E also contains the
same amount of carbohydrates, fats give more energy than carbohydrates for the
same amount.)
1m
iii
C, because it contains the largest amount of proteins which are important for
growth.
1m
iv
E, because it contains carbohydrates only and sugar is a kind of carbohydrates.
1m
b
v
A, because it is rich in vitamin D.
1m
vi
B, because it is rich in vitamin C.
1m
This is because high temperature will destroy vitamin C in food.
1m
Structured questions (p. 5-33)
13
a
One rich
source
carbohydrate potato
Nutrient
One function of nutrient
energy source / energy storage / component
of DNA
fat / lipid
butter
insulation around nerve cells
protein
meat
growth and repair / source of amino acids /
formation of enzymes, hormones and
antibodies OR protein-containing tissue /
energy source
vitamin A
carrot
(good) night vision / allows rods to function /
prevents night blindness
vitamin D
oily fish
absorption of calcium OR phosphate /
deposition of calcium OR phosphate in bones
OR teeth / helps harden bones OR teeth /
prevents rickets
1m x 5
b
c
Bar for pregnancy higher than normal
1m
Bar for breast feeding higher than pregnancy (and normal)
1m
Any two from:
1m x 2
Protein needed to allow foetus / baby to grow / develop
1m
Growth of mother’s cells / tissues
1m
Used for growth of named tissue (maternal or foetal), e.g. placenta, umbilical cord,
bone, muscle
1m
For production of milk
1m
After birth baby growing more quickly
1m
Repair mother’s tissues damaged during birth
1m
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14
a
b
Chapter 5
p.3/5
Different people have different needs.
1m
RNI changes with age / gender / sex / pregnancy / lactation.
1m
i
ii
Any two from:
1m x 2
Inflammation (of eyes)
1m
Scarring / drying of cornea
1m
Loss of sight / blindness
1m
Night blindness / poor vision in dim light / rod cells do not function
1m
Minimum mass of carrot needed =
0 .5
 100  4 g
12
(2m for correct answer and working, 1m for incorrect
answer but correct working, 1m for answer = 4.16)
c
i
ii
15
a
i
Made in skin under sunlight
1m
From cholesterol
1m
Any two from:
1m x 2
Absorption of calcium in gut
1m
Deposition of calcium in bones and teeth
1m
Makes bones hard / stops bones from going soft
1m
Prevent rickets
1m
Mix equal volume of Benedict’s solutions and liquid food sample in a test tube.
1m
Boil the test tube of mixture in a water bath for a few minutes. Observe for any
changes.
0.5m
ii
A brick-red precipitate indicates the presence of reducing sugars.
0.5m
Transfer a drop of liquid food sample to the well of a spot plate.
0.5m
Dip a piece of Albustix paper into the sample and observe any colour change.
0.5m
If protein is present, the paper will change from yellow to green.
b
C and D
1m
0.5m x 2
C shows positive results with iodine test, test using Albustix paper and DCPIP test.
0.5m
D shows positive results with Benedict’s test and iodine test.
c
d
e
0.5m
C: starch, proteins and vitamin C
2m
D: reducing sugars and starch
2m
The carbohydrate may be a non-reducing sugar with a sweet taste. It does not give a
positive result with Benedict’s test because it is non-reducing.
1m
It may be sucrose.
1m
Test for glucose using Clinistix paper.
1m
If glucose is present, the paper will change from pink to purple.
1m
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16
HKCEE Human Biology 1993 I Q4c
17
HKCEE Biology 2000 I Q2a
Chapter 5
p.4/5
Essay (p. 5-35)
18
Carbohydrates contain the elements: carbon, hydrogen and oxygen.
1m
Monosaccharides (e.g. glucose and fructose) are the simplest sugars of which other
carbohydrates are composed.
2m
Glucose is a source of energy. It is the substrate in aerobic and anaerobic respiration. 1m
Two glucose molecules can combine to form a disaccharide, maltose, by condensation.
1m
A glucose and a fructose molecule can combine to form another disaccharide, sucrose, by
condensation.
1m
Disaccharides can be hydrolyzed into monosaccharides.
1m
Polysaccharides are long chains of monosaccharides joined together by condensation.
Starch, glycogen and cellulose are examples of polysaccharides.
2m
Starch provides large number of glucose molecules for respiration.
1m
Glycogen is the storage form of glucose in the body.
1m
Cellulose is the major component of plant cell walls.
1m
Reading to learn (p. 5-36)
1
The amount of carbohydrates in a high protein diet is very small.
1m
When fewer carbohydrates are eaten, the body will break down the stored fat (instead of
carbohydrates) to release energy.
1m
2
Fruits and grains are rich in dietary fibre.
1m
If fruits and grains are not consumed for a long period of time, constipation may result.
1m
3
A high protein diet usually contains a lot of lipids including saturated fatty acids and
cholesterol,
0.5m
which increase the level of cholesterol in the blood.
0.5m
Excessive cholesterol may deposit on the inner walls of the blood vessels and lead to a
blockage. Heart disease may result.
1m
4
No, a high protein diet is not a balanced diet.
0.5m
A balanced diet should contain all the food substances in the right amounts and proportions.
1m
The high protein diet contains large amounts of proteins and lipids,
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0.5m
New Senior Secondary Mastering Biology
Suggested answers to Exercise and Reading to learn
but little or no carbohydrates and dietary fibre.
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Chapter 5
p.5/5
1m