In some plants, a modified leaf forms an insect trap - VCE - SSCE Biology - Question 11 - 2014 - Paper 1
Question 11
In some plants, a modified leaf forms an insect trap. ‘Motor cells’ are located along the midrib of the modified leaf. In their resting state, these cells are turgid... show full transcript
Worked Solution & Example Answer:In some plants, a modified leaf forms an insect trap - VCE - SSCE Biology - Question 11 - 2014 - Paper 1
Step 1
A. When the trap is opening, potassium ions accumulate in the motor cells by diffusion.
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Answer
This statement is not true. During the opening of the trap, the potassium ions actually move out of the motor cells, leading to a decrease in turgidity and an increase in pressure in the surrounding cells.
Step 2
B. When the trap is opening, water accumulates in the motor cells by active transport.
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Answer
This statement is also not accurate. Water does not accumulate in the motor cells as they lose potassium ions; instead, water follows this movement due to osmosis.
Step 3
C. When the trap is closing, potassium ions leave the motor cells because of the pressure in the surrounding cells.
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Answer
This statement is misleading. It is not the pressure alone that causes potassium ions to leave; it is the activation of ion channels that allows the ions to flow out, reducing turgidity.
Step 4
D. When the trap is closing, water leaves the motor cells by osmosis.
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Answer
This statement is correct. As potassium ions exit the motor cells and the turgor pressure decreases, water also exits the cells via osmosis, leading to the closure of the trap.
