ANSWER SCHEME

Paper 1
1. A 21. B
2. C 22. B
3. C 23. D
4. C 24. B
5. C 25. C
6. A 26. C
7. C 27. D
8. C 28. B
9. B 29. C
10. D 30. A
11. C 31. C
12. A 32. B
13. C 33. A
14. D 34. B
15. B 35 B
16. D 36. B
17. C 37. D
18. A 38. A
19. A 39. B
20. C 40. D
Paper 2
SECTION A
1. a) i) Cell W : White blood cell / Neutrophil / Leucocyte
Tissue X : Xylem

ii) Cell W : Prevent infection from bacteria / Engulf / Digest bacteria / Defense
mechanism / Carry out phagocytosis
Tissue X : Transports water and mineral salts from roots to other parts of the
plants

b)  Consists of many small/long appendages

 To increase total surface area per volume ratio

2. a)  Oxygen
 Small/non-polar

b)  Mineral ions cannot be transported into the root hair cells

 No energy for active transport to occur
 No cellular respiration occur to produce energy

c)
(i) Isotonic drink (ii) Oral (iii) Saline
for athlete rehydration solutions for
solutions for medical use
patient with
diarrhoea
Function Water can help to Water replaces the Isotonic saline use
maintain water fluid lost due to in intravenous
content in the diarrhea. Glucose drips (IV) for
body. acts as a source of people who are in
Carbohydrate energy. Salt danger of
provides energy replenish the developing
and minerals electrolytes dehydration. It is
replace the balance in the used to supply
minerals that are body. daily water and
lose through sweat salt needs for the
people who cannot
take fluids orally
 Impact Restore both water Prevent and treat Maintain fluid
and nutrients in dehydration balance and
the body electrolytes in the
body

3. a) i) T = Glucose, U = Fructose

ii) Q = Hydrolysis, R = Condensation

iii)  Break down of sucrose molecules

 Into glucose and fructose
 By adding water molecules

b) i) Cellulose

ii) Glucose

iii)  High tensile strength/strong/tough/rigid

 Can withstand high turgor pressure
 Prevent cell wall from bursting when in dilute solution
 Provides mechanical support

4. a) i) X = Sucrose, Y = Glucose and fructose

ii)

b)  Enzyme sucrase the lock while the substrate sucrose is the key
 The active site of sucrase is specific to sucrose molecules
 Sucrase catalyses the conversion of sucrose molecule into glucose and fructose
5. a)  Reaction rate reaches the maximum level. The rate of reaction is constant.
 At the maximum level, the concentration of enzymes become a limiting factor
 After reaching the maximum level, all active site of enzymes are saturated with
substrate and are involved in the catalytic reaction

b)  Digestive enzymes, used in medical sector

 Lactose enzymes, used in lactose-free milk
 Pectinase and cellulase enzymes, juice production
 Amylase, lipase, protease, cellulase enzymes, used in bio detergent
 Trypsin enzyme, used to extracts fur from animal hide to make leather products
[Any one correct answer]

c)  Inhibitor binds with the active site of enzyme

 Substrate molecule cannot bind with active site of enzyme

6. a) i) P = Anaphase I, Q = Metaphase I

ii) P : Homologous chromosomes separate and move to the opposites of the cell
Q : Homologous chromosomes line up at the metaphase plate / equator of the
cell

b) i)

ii) R = Crossing over

iii)  An exchange of genetic material between non identical chromatids takes
place
 The points where the chromatids cross over is called chiasma
 c) i)  Disruptions to the mechanism that controls the cell cycle will cause the
formation of cancer cell
 Cancer cells compete with surrounding normal cells to obtain nutrients and
energy for growth
 Cancer cell divides uncontrollably through mitosis to form an abnormal
mass of cell called tumour

ii)  Radiotherapy
- High dose of radiation is used to destroy nucleus of cancer cells
- Cancer cells cannot divide by mitosis

7. a) Aerobic respiration

b) Glucose is completely broken down in the presence of oxygen to produce carbon

dioxide, water and energy

8. a) i) Individual R : Aerobic respiration

Individual S : Fermentation

ii) Aerobic respiration Fermentation

The breakdown process of glucose is The breakdown process of glucose is
completed in the presence of oxygen incomplete without oxygen or in
limited oxygen conditions
Occurs in cytoplasm and Occurs in cytoplasm
mitochondrion
Produces water Does not produce water
Glucose is oxidised completely into Glucose is not oxidised completely
carbon dioxide and water into ethanol and carbon dioxide or
lactic acid
One molecule of glucose generates One molecule of glucose generates
2898kJ of energy 210kJ (alcoholic fermentation) or
150kJ (lactic acid fermentation) of
energy
 [Any one answer]
b) i)  When a person sprints, their muscle cells undergo fermentation in the
absence of oxygen to produce ATPs.
 Muscle produce lactic acid that is toxic. Lactic causes muscle fatigue and
muscle pain.

ii)  After doing vigorous activity, the athlete takes fast and deep breathing to
inhale more oxygen to pay oxygen debt
 Excess oxygen is used to oxidise lactic acid into carbon dioxide and water
 Some of the lactic acid oxidised is used to produce energy.
 The remaining lactic acid is convert into glucose and then glycogen which
is stored in the muscle cells
[Maximum : 2]

c) i) Lactobacillus

ii) They cannot survive / they will die

SECTION B
9. a)  Living organism need nutrients/oxygen/glucose/mineral/any suitable example
to continue their life’s processes
 The substances across the plasma membrane from the external environment
 The movement of substances in and out of the cells is regulated by plasma
membrane
 The nutrients/glucose/amino acids/oxygen are transported into the cell
[Maximum : 2]

b) i)  Reverse osmosis works by using a high pressure pump to increase the

pressure on the side with salt solution
 and force the water molecules to move across the reverse osmosis
membrane
 The reverse osmosis membrane is a semi-permeable membrane that
allows the water passage of the water molecules but not the salts
 The pressure applied must be greater than the naturally occuring osmotic
pressure in order to prevent backflow of water
 The amount of pressure required depends on the salt concentration of the
feed water
 The more the feed water, the more pressure is required to overcome the
osmotic pressure
[Maximum : 4]

ii) Advantages
 It keeps the consumer away from water-related diseases
 It has the ability to effectively eliminate many dissolved substances
 Reverse osmosis technology has the capability to remove chlorine taste
and odor

Disadvantages
 Drinking reverse osmosis water dilutes the body of electrolytes
 Reduces the number of beneficial mineral such as calcium and magnesium
in the water
  The water become acidic
[Maximum : 4]

c) i) M : Saturated fats
N : Unsaturated fats

ii)

d)  As an energy source
 As a heat insulator
 Protect internal organs
 Form phospholipid bilayer of plasma membrane
 Aid in fat soluble vitamin absorption
 Form steroid hormones
[Maximum : 5]

10. a) i)  Bromelain/Enzyme remain unchanged after the reaction

 It can continue to bind with other collagen protein molecules to form
enzyme-substrate complex
 and catalyses the break down of / hydrolysis of collagen protein
 repeatedly
[Total : 4]

ii)  As the collagen protein concentration increases, the number of collagen

protein molecule in the reaction increases
 This increases the frequency of effective collisions between collagen
 protein molecules and bromelain molecules
 Bromelain-collagen / enzyme-substrate complexes can be formed at the
higher rate
 The hydrolysis reaction of collagen proteins takes place at a higher rate
 The rate of enzyme reaction increases until it reaches the maximum point
 which all the active site of bromelain molecules are occupied by the
collagen proteins
 Any further increase in collagen protein concentration does not result in
an increase in the rate of enzyme reaction
 The concentration of bromelain becomes a limiting factor
[Maximum : 6]

b)  Baby still not able to produce enough enzyme

 Protein/lipid are are large/complex molecule
 Enzyme protease/lipase break down
 food/protein/lipid into simpler molecules/undigested food
 Easier for baby to absorb nutrient/food
[Maximum : 4]
SECTION C
11. a) i)  The cell that can be divided into new cells of the same type, and
 differentiate into other types of cells to carry out specific function
[Total : 2]

ii) Yes
 Stem cells are collected from the blood or bone marrow of a healthy
donor/umbilical cord blood
 The stem cells can differentiate into healthy/specific blood cells
 to replace cells damaged by chemotherapy or disease
 The stem cells also contain immune cells to fight leukaemic cells
[Total : 5]

b) Name
 Down syndrome
 A type of genetic disease
Cause of disease
 Abnormality during division of meiosis
 Spindle fibres fail to function during anaphase I / anaphase II
 As a result, chromose fails to separate
 Gametes produced have an abnormal number of chromosomes / 22 or 24
chromosomes
 Fertilisation between a normal gamete (gamete with 23 chromosomes) and an
abnormal gamete (gamete with 24 chromosomes)
 An abnormal zygote / zygote with 47 chromosomes is formed
 An individual with Down syndrome has an extra chromosome at the 21st set /
trisomy 21
Syndrome
 Mental retardation / slanted eyes / protruding tongue
[Maximum : 8]
c)  Meiosis results in production of haploid gametes from diploid cells in
reproductive organ of an organism
 One haploid female gamete is then able to fuse with one haploid male gamete
 To form a diploid zygote during fertilisation
 The diploid zygote then undergoes mitosis and grows into a new organism
 that has the same number of chromosomes as the normal body cells of the
parent
 Hence, meiosis can ensure the diploid number of chromosomes in a species is
maintained from generation to generation
[Maximum : 6]