Download PCGHS March Test ~ Year 2009 ~ Upper Six BIOLOGY Mark

PCGHS March Test ~ Year 2009 ~ Upper Six BIOLOGY Mark Scheme
Page 1
Suggested Mark Scheme
Item
1 (a)
(i)
(ii)
(b)
(i)
Answers / Points
Endodermis
Xylem
Casparian strip / suberin impermeable / barrier to water movement (idea
of waterproof, not waxy)
Water enters cell along water potential / osmotic gradient / by osmosis
A – sinoatrial node / SA node / SAN / pacemaker
B – atrioventricular node / AV node / AVN
C – Bundle of His / arioventricular bundle / AV bundle
D – Purkinje fibre / Purkyne fibre
Mark
1
1
1
1
3
max
(All correct – 3 marks;
Three correct – 2 marks;
One or two correct – 1 mark)
(ii)
Give time for the cardiac muscle of atria to finish contracting (and force the
blood to flow from atria to ventricles).
or
Allow atria ample time to empty its blood completely into the ventricles
before the ventricles contract.
(iii)
Stretch receptors in the aortic arch and carotid sinuses detect:
Increases in blood pressure
1
2
max
Chemoreceptors in the carotid body detect:
Increases in PPCO2
Decreases in blood pH
2 (a)
(i)
Subtotal
The maintenance of the internal environment of a living organism at a
constant level / within a narrow range of limits.
10
2
Alternatively:
The process of maintaining a constant internal environment in an
organism.
(ii)
Correct graph for endotherm – 1 mark
Correct graph for ectotherm – 1 mark
2 (b)
(i)
Urea / glucose / amino acids / fatty acids / glycerol / (inorganic) ion
(one mark for two of above)
Prepared by CBYeap
2
1
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PCGHS March Test ~ Year 2009 ~ Upper Six BIOLOGY Mark Scheme
(c)
(ii)
(Less blood pressure / Blood pressure decreased) forms less filtrate
Rate ↓
1
(iii)
Decrease in insulin production / receptors not responsive to insulin
or
Specific damage to tubule / membrane less permeable to glucose
1
(iv)
Glucose reabsorbed/absorbed into blood from proximal tubule
By active transport / involving membrane carriers
1
1
(i)
i. Carbohydrate metabolism.
ii. Protein metabolism.
iii. Bile production.
iv. Storage of vitamins and minerals.
v. Detoxification.
vi. Lipid metabolism.
vii. Storage of blood.
viii. Breakdown of haemoglobin.
viiii. Hormone production and breakdown.
x. Heat production.
(1 pairs correct – 1 mark)
5
max
(ii)
6
.
Subtotal
Twice.
20
1
Citrate (6C) is converted to α-ketoglutarate (5C).
α-Ketoglutarate is converted to succinyl CoA (4C).
1
1
(i)
Cristae / inner membrane of mitochondrion
1
(ii)
Electrons / hydrogen combine with NAD or FAD / NADH or FADH in
correct context
1
Electrons passed through series of carriers and energy released during
the transfer
1
Energy used to make ATP from ADP and inorganic phosphate (reject P,
accept Pi) / using ATPase
1
3 (a)
(b)
Prepared by CBYeap
Page 3
PCGHS March Test ~ Year 2009 ~ Upper Six BIOLOGY Mark Scheme
R : β-oxidation
P : Glyecerol
Q : Fatty acids
(c)
3
Subtotal
4 (a)
(i)
Light reaction – granum of chloroplast
Dark reaction – stroma of chloroplast
(ii)
Photolysis / Cyclic photophosphorylation / Non-cyclic photophosphorylation
(Three correct – 2 marks; one or two correct – 1 mark)
10
1
1
2
(iii)
Cyclic
Photons
ADP
Phosphate group
Non-cyclic
Photons
Water
ADP
NADP+
Phosphate group
ATP
ATP
Oxygen
1
Captured energy in the form of
ATP
Captured energy in the form of
ATP and NADPH
1
NADPH2
1
(List out completely; otherwise, no mark)
(b)
(i)
C3 plants
High [CO2] only exist in
mesophyll cells.
CO2 receptor is RUBP.
RUBP carboxylase is
inefficient at low [CO2].
First product formed is
glycerate 3-phosphate, a 3C
compound.
Photorespiration occurs. O2
acts as competitive inhibitor
Less efficient photosynthesis
rate. Photosynthetic yield is
lower.
No Krantz anatomy in the
leaf.
Only 1 type of chloroplast is
found in mesophyll cells.
C4 plants
High [CO2] exist in mesophyll cells and
bundle sheath cells.
CO2 receptor is PEP in mesophyll cells
and RUBP in bundle sheath cells.
PEP carboxylase has a higher affinity
for CO2 at low [CO2].
First product formed is oxaloacetate, a
4C compound.
3
max
Photorespiration is inhibited by high
[CO2] (due to Krantz anatomy).
Photosynthesis is efficient. Yield is
much higher.
Krantz anatomy present.
Two different forms of chloropast:
 Palisade mesophyll cell contain
few small chloroplasts, many large
well-developed grana but no starch
grains.
 Bundle sheath cells have many
large chloroplasts with fewer
poorly developed grana and starch
grains.
Either three above for three marks.
Subtotal
Prepared by CBYeap
10
Page 4
PCGHS March Test ~ Year 2009 ~ Upper Six BIOLOGY Mark Scheme
5 (a)
(b)
(i)
A : carbonic acid (H2CO3)
B : carbonic anhydrase
(ii)
Lowers the surface tension of the fluid lining the inner surface of the
alveolus
1
Speeds up the rate of gaseous exchange
1
(i)
Draw a curve to the right of curve for pH 7.4
1
(ii)
More oxygen unloaded / given up / affinity decreased /
reduced saturation
1
Oxyhaemoglobin dissociates at higher oxygen concentration/
partial pressure / more oxygen unloaded at the same PPO2
1
Aerobic respiration will produce carbon dioxide which dissolves in blood
forming acid
or
Anaerobic respiration produces lactate / lactic acid
1
(Both or either one type of the respiration) Increase hydrogen ion
concentration
1
(iii)
Prepared by CBYeap
C : Bohr
D : chloride
4
Subtotal
10
TOTAL
60