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5d) The blood pressure drops as blood flow from aorta to the capillaries. What is the significance of having lower blood pressure in the capillaries?

Classmate's answer:
It allows blood to flow more slowly so that the time for exchange of materials between blood and tissue cells increase.

Wrong concept:
Low velocity of blood flow cause the increase time for exchange of materials between blood and tissue cells, but not low blood pressure.

The significance of having low blood pressure is to prevent the damage of capillaries wall.

Suggested answer:
Since the capiilary is thin, lower blood pressure prevent the damage of delicate capillary wall.

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2biii)
Wrong ans. Mechanoreceptor
Suggested Answer:Sensory Hair Cells inside the cochlea

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6(b)
wrong answer:  0-1 , 3-6s as air is forced out of the lung and also during exhalation, the rib cage move inward and downwards and the volume of lung decrease hence the air pressure inside is larger.
Correct answer: 0-2,4-6s  because the lung pressure is higher than the atmospheric pressure.

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Classmate's answer: 10(c)(I) waterlogged soil will draw water from root hair cells by osmosis.
Wrong concept:waterlogged soil means no water
Suggested answer: waterlogged soil means soil with many water. The oxygen content in the soil is very low. There's insufficient amount of oxygen for root cells to carry out respiration to release energy for the active transport of minerals. So the cells cannot absorb enough minerals

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Q9b
Classmate's answer: epidermal cell is impermeable to water in fluids therefore water cannot enter the epidermal cell. Osmosis cannot occurs
Correct answer: because the cuticle on the surface of epidermal cell is impermeable to water so osmosiscannoy take place.

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Q10c
classmate 's answer: when soil is waterlogged, oxygen content decrease and the rate of active transport decrease.There are not enough minerals absorbed by root hair cell.so the water potential of the root hair cell is higher than the soil so water can't be absorbed through osmosis.
wrong concept: not mention oxygen and active transport need energy.
Suggested answer:with waterlogged soil,plants can't have enough oxygen for respiration.As pathway A is absorbing mineral from soil into cells by active transport, which need energy. Lack of oxygen will lower the rate of active transport so less mineral is absorbed.

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Question 4(a) Suggest why the tubes of enzyme and milk were kept a water bath at temperature for 15 mins before they are mixed.

Classmate's answer:
To allow time for the enzyme to work.
Wrong concept:
not about time
Should be related to the nature of protein
Suggested answer:
to allow the enzyme and egg white to reach the required temperature before they are mixed.

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Q9)Ii) give a reason in solution A
The concentration of sucrose of solution A is similar to the stalk
There is no net flow of water

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Question 4(e):

Classmate's answer:
No, there will not be changes. In 60 degrees, the enzyme was denatured by the high temperature, once it is denatured, it cannot return back to its original state and can no longer function. Even the mixture was cooled to 40 degrees, the enzyme will not change and are still destroyed. There will be no change in the result.

Correct answer:
There will be no change. When temperature is too high, the shape of enzyme molecule is changed permanently. The active site no longer fits the substrate molecule and there is no reaction.

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Question: Q10c ii)

Answer: The carrier proteins on the cell membranes which involved in pathway B help the absorption of minerals by active transport as it can absorb against a concentration gradient when the mineral concentration in soil is higher than that in plant which requires energy to transport to inside.

Wrong concept: Fully permeable cell wall instead of cell membrane. Diffusion instead of active transport.

Suggested answer: The high concentration of mineral ions in soil forms a concentration gradient which leads to the diffusion of mineral ions across the fully permeable cell wall through pathway B.

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Q5a
Classmates answer: allow longer time for exchange of materials
Wrong concept: unable to understand the question
Answer:lower blood pressure prevents a build up of tissue fluid

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Question 5a
Classmate's answer: The left ventricle provides a strong force of contraction to drive blood throughout the body, and thus the pressure is high. The left ventricles contracts and relaxes, causing the blood pressure to have big fluctuations. Aorta drives blood with high pressure throughout the body by the pumping action of the heart.

Correct answer: The minimum blood pressure in the aorta is much higher than that in the left ventricle. Because recoiling of aorta helps maintain the blood pressure

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Classmate's answer: No, the response of covering the ears involves in the action of cerebrum San te nerve impulse generated by the sensory hair celll is transmitted to the association area of the cerebrum for interpretation and judgement, then a new impulse of covering the ears is initiated by cerebrum and sent to muscle through motor neurone

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Question 5b
Classmate's answer: The right ventricle is responsible for pumping the blood to the lung for gas exchange while the left ventricle needs to pump the blood to the whole body. As the distance travelled is smaller, the force needed to pump is smaller. Hence, the pressure in the right ventricle is lower.
Correct answer: Missing point-left ventricle has a thick, muscle layer

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(28) Q9b. Classmates' answer: A fully permeable cell wall is present in cortical cells which allows sucrose solution to freely diffuse in and out. However, the sucrose solution is too large to pass through the differentials permeable membrane.
Suggested changes: The outer surface of epidermal cell is covered with cuticle which is impermeable to water.

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classmate work : 5(d) allow blood to flow more slowilu so the time for exchange of  materials between blood and tissue cell increases.

Wrong concept: lower pressure results in protection towards the thin and one cell thick capillary instead of facilitating exchange of materials.

Wrong observation: the focus should be put on lower pressure instead of lower velocity

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Q5a
Classmate's answer:
The blood pressure of the left ventricle is much larger than that of the aorta. They both receive high blood pressure due to the pumping force of the heart, but as the aorta has thick walls which can withstand the high blood pressure and a smaller lumen which slowers the movement and reduce pressure, the pressure in the aorta is less than the left ventricle.

Wrong concept:
The wall does not affect blood pressure, instead, it is elastic muscle.

Wrong observation:
The blood pressure of the aorta and the left ventricle is similar, but won't reduce as much as rye left ventricle

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3a)   Comparing the results of experiments 1 and 2, what conclusion can be drawn?

Classmate's answer:
Pancrea is important and main reason causing diabetes showing the component inside pancreas help catalyse the breakdown of glucose in urine.

Wrong concept:
Did not state the differences between the two experiments.
Should be more specific about what component it is inside pancreas for disappearance of symptoms.

Suggested changes:
From experiment one and two, it's shown that pancreas contain substances that are essential for the disappearance of symptoms. Thus pancreas may have produced juice or enzymes or other substances for it.

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Question: 5(d) The blood pressure drops as blood flows from the aorta to the capillaries. What is the significance of having lower blood pressure in the capillaries?

Student's answer: With lower pressure caused by high resistance of small lumens of capillaries and larger total cross-sectional area, blood flows more slowly, allowing more time for more thorough exchange of materials between capillary walls.

Wrong concept: speed of blood flow is related to low blood pressure of blood in capillaries

Correct answer: The capillary wall is thin/one-cell thick.
A high blood pressure would damage the capillary wall./ A lower blood pressure prevents a build-up of tissue fluid.

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Question:
(7)(bii)

Classmate's answer:
As biceps and triceps are opposing muscle which work together to coordinate and bring out a movement, the hand bends when biceps contract and triceps relax, the hand straighten when bicep relax and triceps contract.

Missing points:
Triceps is the extensor

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Question:
Identify solution b. Give reasons for your answers.

Classmates answer:
Distilled water. As distilled water has a higher water potential than the flower stalk, the water molecules in distilled water will get into the cell membrane of the flower stalk by osmosis. The vacuole and cell membrane is turgid, making the flower stalk to have a larger volume than before.

Missing answer:
1. The process of osmosis
2. Conclusion of the resulted shape

Suggested answer:
Solution B is distilled water. When he flower stalk is placed in distilled water, the water potential of distilled water is higher than that of the flower stalk. Water enters from the distilled water to the cortical cells of the flower stalk. As more water enters, the cortical cells become turgid and full, but has a rigid cell wall to withstand it. The cortical cell becomes more turgid than the epithelial cells, thus result in the shape in the figure.

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Questions:
3(b) Describe how the foetus obtains nutrients for growth.

Classmates' answer:

The foetus' belly button is connected by the umbilical cord which supply nutrients and oxygen though the arteriolar. The mentation blood and the foetus blood are separated to ensure the transporting in nutrient and oxygen, removing of waste like urea and carbon dioxide.

Wrong concepts:

1. Exchange of materials through placenta instead of umbilical cord

2. Missing point about diffusion from maternal blood into foetal blood.

3. Separation of maternal and foetal blood is irrelevant to the question and does not ensure the exchange of substances

Suggested changes:

The foetus obtains nutrients through the placenta on the wall of uterus of mother. Nutrients are passed from the mother to the foetus through the umbilical vein. The nutrients like glucose diffuses through the capillaries of placenta to reach the foetus blood