Answer of revision exercise of Ch 4
(a)
Substance A was taken up by amoeba at a constant rate throughout the six hour.
Substance B was taken up during the first five hours.
After five hours, the uptake of substance B stopped.
The uptake rate of A was greater than that of B.
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(b)
By diffusion
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The uptake rate was higher in the beginning of the experiment as the concentration difference between
the amoeba and the solution was larger.
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The uptake rate decreased as the amoeba had taken up more substance B and the concentration
difference between the cell and the solution became smaller.
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The uptake finally stopped when the concentration of substance B inside the cell was the same as the
concentration outside the cell.
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(c)
The uptake rate of substance B will increase.
An increase in temperature will increase the kinetic energy of molecules,
therefore the molecules of substance B will move into the amoeba faster.
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(d)
active transport
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