PraPSPM LABUAN SB025 20-21 ANSWER SCHEME-converted

Answer scheme PRA PSPM SB025 2020/2021

Questions Answer Scheme Marks
1
1(a)(i) Process M: Decomposition 1

Process N: Combustion/ Burning

(ii) Fossil fuels/ natural gas/ petroleum/ oil and gas 1
1
Sunlight

(iii) 6CO2 + 6H2O C6H12O6 + 6O2

Chlorophyll

(iv) Reforestation// Carbon sequestration//plant more tree// any acceptable answer 1

(b)(i) Zone I: Littoral zone 1
Zone II: Limnetic zone 1

(ii) Distance from the shore and water depth 1
2(a)(i) Total 8
1
A process of selection where individuals which are better adapted / more fit will
survive and produce more offspring / have higher reproductive success.

(ii) Natural selection Artificial selection

Selection force/ agent is nature Selection force/ agent is human 1/0
1/0
Speed of selection is slow Speed of selection is fast/rapid 1/0

Parents of offspring are not Parents of offspring are consciously
consciously chosen chosen

Random event Planned event 1/0

Occurs in natural population Occurs in domesticated population 1/0
(Any 2)
(b)(i) Tigers and lions are not able to produce fertile hybrid offspring / hybrid
breakdown in F1 generation / produce infertile offspring 1

(ii) Through allopolyploidy / doubling of chromosomes in hybrid offspring 1

(c)(i) Mode P Mode Q
Occurs in geographically isolated Occurs in geographically overlapping
populations populations / in the same habitat 1/0
Geographical barrier is present Geographical barrier is not present
1/0
Total (Any 1)

3(a) Transferases 6
1

(b)(i) Induced Fit Model 1
Shape of the active site and substrate are not exactly complementary / are not 1
perfectly matched
Binding of substrate induces conformation changes in the enzyme that maximize 1
the fit and force the complex into a more reactive state. (Any 2)

(ii) The enzyme will denature 1
PRA PSPM SB025 2020/2021

(c)(i) Act as non-competitive inhibitor 1
1
(ii) Increase enzyme concentration// Remove substance X Total 6
1
4(a)(i) Process A: Glycolysis 1
Molecule M: Glucose 1
Molecule N: Lactic acid/ Lactate 1

(ii) Oxidation of M in skeletal muscle able to produce ATP//ATP still can be 1
(iii) produced 1
(b)(i) 1
(ii) Both produce (2) ATP by substrate level phosphorylation 1
1
(c)(i) Aerobic respiration 1
(ii) Presence of oxygen 1
(d) 1
Electron flow along the electron transport chain will be accepted by oxygen/ 1
5(a)(i) oxygen is the final electron acceptor in electron transport chain 1
Oxygen then will combine with hydrogen ions from the matrix of mitochondria to 1
form water molecule
15
18 (oxygen) 1
1
18 (carbon dioxide) 1
1
Less oxygen/ absence of oxygen that can act as final electron acceptor in electron
transport chain 1
Electron transport chain remains in reduced state due to accumulation of electron 1
as the electron flow is blocked 1/0
Hydrogen ion cannot be pumped to the intermembrane space to create a proton 1/0
gradient/ proton motive force
Inhibit production of ATP// less/ no ATP will be produced 1

Total
Photorespiration
Rubisco has higher affinity toward oxygens at higher concentration of oxygen
Oxygen act as competitive inhibitor// Rubisco catalysed the binding/ fixation of
RuBP with oxygen
Reduced the efficiency of photosynthesis// reduced the product of
photosynthesis// reduced the production of 3-phosphoglycerate

(ii) Oxygen act as competitive inhibitor to carbon dioxide

(b) By using CAM pathway and open stomata during the night

(c) Carbon dioxide acceptor in C3 plant is RuBP while carbon dioxide acceptor in C4
plant is PEP and RuBP
Enzyme involved in carbon fixation of C3 plant is RuBP carboxylase/Rubisco
while in C4 plant is RuBP carboxylase/Rubisco and PEP carboxylase

(d) Malate is transported out of the vacuole into the cytoplasm in the morning (which
then will undergo decarboxylation)

PRA PSPM SB025 2020/2021

Total 9
6(a) In skeletal muscle (tissue) 1
1
Myoglobin has high/ strong affinity toward oxygen 1
It only releases oxygen when partial pressure of oxygen very low/ extreme
condition/ below 20 mmHg

(b) Carbon dioxide is fixed, reducing its concentration Total 1
pH rises 1
Starch is converted into sugar 1
Water potential decreases causing water to enter the guard cell 1
Guard cell becomes turgid forcing stomata to open 1
(Any 3)
7(a)(i) Act as pacemaker 6
To initiate heartbeat by generating electrical impulse 1
1

(ii) - A (SA node) generates electrical impulse and spread across both atria 1
causing atrial systole (contract)// Blood enter the left and right atrium from 1
pulmonary vein and vena cava respectively causing increase in blood pressure 1
-impulses are passed to AV node and delayed for 0.1 second // blood is pumped 1
from atrium to ventricles for 0.1 second 1
-impulses (from AV node) are conducted by bundle of His to Purkinje fibres 1
-Purkinje fibres transmit impulses throughout both ventricles and toward the apex 1
-causing ventricular systole 1
-blood pressure is higher than in atrium 1
-blood is pumped from left and right ventricles to body and lungs respectively 1
(Any 5)
(b)(i) Mineral ions are transported by active transport into the root cortex Total 1
8(a) Thus, more mitochondria are needed to provide energy for active transport 1
9
A: Bowman’s capsule 1
C: Distal (convoluted) tubule 1

(b) Ultrafiltration 1

(c) High hydrostatic pressure in the glomerulus/ diameter of afferent arteriole is 1
larger than efferent arteriole// Highly coiled glomerulus// High permeability of
glomerulus

(d) More ADH are secreted (by posterior pituitary gland) 1
Increase the permeability of collecting duct to water 1
More water is reabsorbed 1
Small amount of concentrated urine is produced 1
(Any 2)
9(a)(i) Total 6
X: Mitochondria 1
Function: To provide ATP for the synthesis of neurotransmitter// reuptake of 1
neurotransmitter

(ii) Depolarization of sarcolemma will not occur 1

PRA PSPM SB025 2020/2021

(iii) Z is sarcomere 1
Molecule P will bind to the receptor at motor end plate and causes the opening of 1
ligand-gated Na+ channel
Influx of Na+ into muscle cell causes depolarization and Z will shorten/ contract 1

(iv) Sliding Filament Theory 1

(v) Y will disappear 1

(b) Neuromuscular junction Along Axon 1/0
Involves neurotransmitter No neurotransmitter 1/0
Impulse is chemically transmitted Impulse is electrically transmitted 1/0
Involved voltage gated Na+ Involved both voltage gated Na+ and
channel// does not involve voltage K+// involve voltage gated K+ channel 1/0
gated K+ channel
Ion/ Na+ channels found on Ion/ Na+ channels along the axon 1/0
membrane of motor end plate membrane 1/0
Leads to depolarization Leads to action potential
Speed of impulse transmission is Speed of impulse transmission is faster 1/0
slower
Presence of Ca2+ channels/ involve No Ca2+ channels/ does not involve 1/0
diffusion of Ca2+ diffusion of Ca2+ (Any 1)
Involve receptor protein Do not involve receptor protein
1
(c)(i) Gene Activation
1
(ii) cAMP/ second messenger activation

Gene activation cAMP activation 1/0
Hormone can diffuse through Hormone cannot diffuse through plasma 1/0
plasma membrane of target cell membrane of target cell
Hormone binds with receptor in Hormone bind with receptor in plasma 1/0
cytoplasm to form hormone- membrane to form hormone-receptor 1/0
receptor complex complex (Any 1)
Hormone-receptor complex activate Hormone-receptor complex activate G-
gene on DNA protein
Transcription and translation occur Transcription and translation does not
occur

(iii) Mechanism is not activated Total 1
13
10 Cell mediated immunity
Humoral Immunity Involve cytotoxic T cells 1/0
Tc cell is produced in the bone 1/0
Involve B cell/ lymphocytes marrow, mature in the thymus gland
B cell is produced and mature in the
bone marrow

PRA PSPM SB025 2020/2021

Involves production of antibodies Tc cell produce perforin to produce 1/0
pore in the infected cell// Directly kill/
Pathogens identified - via antigens attack the infected cell 1/0
floating in the blood Pathogens identified - via antigens on 1/0
Pathogens are killed by antibodies. the surface of infected cells. 1/0
Pathogens are killed by specialised 1/0
B cell divide into plasma cells and killer T / cytotoxic T cells
memory B cells. Tc cells divide into active Tc cell and
memory T cell ( different types of
Defend against extracellular pathogen specialist T cells)
Defend against intracellular pathogen

Total 6

PRA PSPM SB025 2020/2021