Answer Scheme Trial SPM (SBP 20090 Paper 2 Section B
No 6
Marking Criteria
Marks
(a) (i)
Able to describe the mechanisms in organelle M that
involved in the formation of starch in the plant.

Sample answer :

P1: The formation of starch in plants is by the process of
photosynthesis which occurs in chloroplasts.

P2: The two stages in photosynthesis are the light and dark reactions.

Light reaction:
P3:Takes place in grana.

P4: Chlorophyll captures light energy which excites the electrons of chlorophyll molecules to higher energy levels.

P5: In the excited state, the electrons can leave the chlorophyll molecules.

P6: Light energy is also used to split water molecules into hydrogen ion (H+) and hydroxyl ions (OH-) (Photolysis of water).

P7: The hydrogen ions then combine with the electrons released by chlorophyll to form hydrogen atoms.

P8: The energy from the excited electrons is used to form energy-rich molecules of adenosine triphosphate /ATP.

P9: Hydroxyl ion loses an electron to form a hydroxyl group. This electron is then received by chlorophyll.

P10: The hydroxyl groups then combine to form water and gaseous oxygen.

Dark Reaction:
P11: Take place in stroma.

P12: Do not require light energy.

P13: The hydrogen atoms are used to fix carbon dioxide in a series of reactions catalysed by photosynthetic enzymes

P14: and caused the reduction of carbon dioxide into glucose.

P15: The glucose monomers then undergo condensation to form starch which is temporarily stored as starch grains in the chloroplasts.

any 10P


(b)(i)
Able to suggest two health problems which that teenager could have if she continuously taking the above menu for a long time.

Sample answer :
F1: Chronic heart disease

P1: Her diet contains large amounts of oil/cream/fat and it causes arteriosclerosis / atherosclerosis / heart problem / cardiovascular disease.

F2: Constipation.

P2: Lack of fruit/vegetables / fibers leads to constipation.

4
(b)(ii)
Able to explain ways to improve daily food intake and stating the reasons for the choice of food.

Sample answer :

P1: Drink scheme milk/low fat milk and eat a boiled egg to reduce the cream and fat from her diet

P2: Replace sausage with an orange to increase her fruit fibre intake

Lunch:
P3: Drink fresh fruit juice because it has lower sugar content/more vitamins

P4: Eat steamed rice/steamed chicken to lower cholesterol intake

P5: Eat vegetable/salad to increase the amount of roughage

Dinner:
P6: Drink clear soup to reduce the cholesterol

P7: Use tomato sauce with her pasta because it contains less fat and more fibers.

P8: Eat a slice of watermelon/any fruits to increase her intake of fiber to prevent constipation
Any 6


TOTAL 20 marks


No 7
(a)

Able to explain what cloning is :

Sample answer :

P1 : Cloning is an asexual reproductive process of producing clones//does not involve gamete
P2 : A clone is a group of cells//organism//a population of organisms produced from a single ancestral cell.
P3 : A clones genetically identical
P4 : The technique can be used to produce high quality of organism / orchids/ oil palm / cocoa plants.
Any 2 P
(b)
Able to describe tissue culture technique.

Sample answer:

P1 : Tissue culture technique

P2 : Tissue culture technique is used to produce (high quality of seedling)oil palm seedlings in vitro/any suitable example.

P3 : The leaves/shoot/stem/root tissues are cut out.(These cut out plant tissues are called explants).

P4 :The pieces of meristematic tissue (explants) are cultured in sterile nutrient medium, in suitable pH and with addition of plant growth substances.( at least 2 factors)

P5 :The flasks containing the tissue are stored in an incubator at 37°C for 2/3 weeks.

P6 : The cell divide by mitosis to produce callus.

P7 : The callus is then cut into small pieces.

P8 : The small pieces of callus tissues are then cultured in sterile nutrient medium.

P9 : When it has grown to a suitable size, the clone is transferred to the nursery.

Any 6 P

(b)
Able to discuss Advantages / strength:

P1 : Genetic engineering involves genes manipulation / transfer / modification in organisms to produce certain products.

P2 : Example; products in pharmacy such as insulin / antibiotics; food products based on plants / animals; agricultural / agrochemical products.

P3 : The products produced are very similar to the original / natural materials because the same genes are used / particularly chosen genes are transfered.

P4 : The production of products is faster especially with the use of microorganisms/bacteria.

P5 : Microorganisms such as bacteria are suitable to be used as gene vectors / they have free DNA in the form of ring / plasmid.

P6 : High reproduction rate of bacteria/microorgansm in optimal culture mediums able to produce a large amount of chosen genes / products / insulin / antibiotics.

P7 : Can be used by thousands of people who need them / widespread usage.

P8 : Able to produce a variety of proteins / recombinant proteins / enzymes used in food industries / medicine / agriculture.

P9 : Genetic engineering technique is used to solve criminal cases through DNA finger printing / DNA fragments analysis.

P10 : Other uses /examples; metal extraction from oxide/any suitable examples

Any 6 P


(c)


Able to describe the effect of cycle malfunctions to the body.

Sample answer
P1: The exposure damage the DNA of the cell

P2: A cell divides through mitosis repeatedly.

P3: Produces cancerous cell

P4: Due to (severe ) distruption to the mechanism
that controls the cell cycle

P5: Cancerous cells divide freely / uncontrollably
heeding the cell cycle control

P6: (these cells ) compete with surrounding normal
cells to obtain nutrient / energy (for growth)

P7: Invade / destroy neighbouring cells

P8: (they can spread to other organ and) initiate
cancers there .
Any 6 P

TOTAL 20 marks


No 8
Marking Criteria
Marks

(a)

Able to describe the movement of water from root to the leaf which aided by :
Root pressure
Capillary action
Transpirational pull

Sample answer:

Root pressure

P1: The cell sap of root hair (usually) hypertonic to the surrounding soil solution
P2: Water diffuses into the root by osmosis.

P3: (As they absorb more water by osmosis), a cell sap becomes more dilute compared to neighbouring cells.

P4: Water (therefore) moves to these adjacent cells which become more diluted themselves, so osmosis continues across the cortex

P5: (At the same time), ions from the soil are actively secreted into the xylem vessels and this causes osmotic pressure to increase

P6: Water flows continuously into the xylem and this create a pressure known as root pressure

P7: Root pressure gives an initial upward force to water and mineral ions in the xylem vessels

Capillary action

P8 : Water moves up through the xylem in the stems by capillarity (with is the upward movement of a fluid in a narrow bore tube)

P9: Capillary action is due to combined force of cohesion (water molecule have attraction for each other) and adhesion (water molecules are attracted to the side of the vessels)

P10: Water molecule form a continuous water column in the xylem vessel (due to cohesion and adhesion force enable water to move up along the xylem vessels)

P11: (As water is pulled upwards) the cohesion of water (which is due to hydrogen bonding holds the water molecule together) prevent the water column in the xylem breaking apart

P12: (At the same time) the adhesion of the water (to the wall of the xylem vessel and tracheids) prevents gravity from pulling the water down the column

Transpirational pull

P13: The lost of water from the mesophyll cells during transpiration is replaces by water which flows in from the xylem vessels in the leaves

P14: This creates a tension / suction force in the water column because water has cohesive properties called transpiration pull

P15: The transpiration pull draws water from the xylem in the leaves/stems/roots.

P16: The continuous flow of water through the plant is known as the transpiration stream

Max 4

b (i)
Able to explain the diffrences of composition fluid P and fluid Q

Sample answer:

F1: Fluid Q/lymph has a larger numbers of lymphocyte compare to fluid P/blood

P1: lymphocyte is produced by the lymph nodes in lymph system

F2: Fluid Q/lymph has lower contents of oxygen compare to fluid P/blood
P2: oxygen has been used up by the cell

b(ii)

Able to describe how lymph is formed from blood until it is brought back into the blood circulatory system.

Sample Answer :

P1: (When the blood flows from arteries into capillaries)there is higher hydrostatic pressure at the arterial end of the capillaries

P2: (This high pressure) forces some plasma to pass through the capillary walls into the intercellular spaces (between the cells)

P3: Once the fluid leaves the capillary walls, it is called interstitial/tissue fluid // The interstitial fluid fills the spaces between the cells and constantly bathes the cells

P4: 90% of the interstitial fluid diffuses back into blood capillary

P5: 10% of the interstitial fluid that has not been reabsorbed into the bloodstream goes into the lymph capillaries.(Once inside the lymph capillaries) the fluid is known as lymph.

P6: The lymph capillaries unite to form larger lymphatic vessels.

P7: From the lymphatic vessels, lymph eventually passes into the thoracic duct/the right lymphatic duct.

P8:The thoracic duct empties its lymph into the right subclavian vein. (Hence, lymph drains back into the blood).

Any 6 P

Max 6

TOTAL 20


No 9
Marking Criteria
Marks
(a)
Able to state the Sequence of events that occur when the hand touches a hot object.

Sample answer :
P1: the heat on the object stimulates the nerve endings (receptors) in the skin.

P2: impulses are triggered.

P3: This impulses travel along the sensory/afferent neurone to the spinal cord.

P4: in the spinal cord, the impulses are transmitted first across a synapse to the interneurone and then across another synapse to the motor/efferent neurone. ( at least 2 type of neurone)

At synapse
P5: When an impulse reach a presynaptic membrane, it triggers the synaptic vesicles to release neutrotransmitter into the synaptic cleft.
P6 The neurotransmitter diffuse across the synaptic cleft

P7: and bind to receptors which are attached to the postsynaptic membrane.

P8: The binding of the neurotransmitter to the receptors leads to the generation of a new impulse

P9: Impulses leave the spinal cord along the motor/efferent neurone to the effector

P10: the effector is the biceps muscle which then contracts. This brings about a sudden withdrawal of the hand.

Any 8

(b) (i)

Able to explain how geotropism is brought about in a plant root and shoot.

Sample answer :
Diagram :
Shoot
Root


Correct Diagram ( shoot grows upward, root grow downward): 1 m

Shoot
P1 : The auxin that is produced at the tip of shoot.

P2 : auxin moves downward/ accumulate on the underside of the shoot tip due to the pull of gravity.

P3 : the high concentration of auxin accelerates the growth

P4 : stimulating greater cell elongation on the underside relative to the cells on the upper side.

P5 : this differential elongation causes the shoot to bend away from gravity / grow downwards.

Root
P6 : The auxin that is produced at the tip of root.

P7 : auxin moves downward/ accumulate on the underside of the root tip due to the pull of gravity.

P8 : the high concentration of auxin inhibits the growth

P9 : slowing down cell elongation on the underside relative to the cells on the upper side.

P10 : this differential elongation causes the shoot to bend towards gravity / grow downwards.

Any 7 P

(b)(ii)
Able to explain the advantages

Sample answer

Advantages

Explanation
F1
ensures the root grow/penetrate deep into soil
P1
To anchor the plant firmly in the ground
F2
The roots always contact with the soil water/mineral/nutrients
P2
To maintain turgor pressure/ growth/ photosynthesis

F3
Ensure that the leaves of shoot growth towards sunlight
P3
To absorb maximum amount of light energy for photosynthesis.


Any 2 F with correspond P

4

TOTAL
20