Video Transcript
The diagram shows a simplified
outline of a root hair cell and the movement of calcium ions from the soil into
it. What process is being shown by the
movement of calcium ions in the diagram?
Mineral ions are essential for many
different plant functions. For example, calcium ions play an
important structural role in plant cell walls and cell membranes. Generally, plants absorb these ions
through their roots from soil, and many plants have specialized root hair cells to
aid in this absorption.
There are two main ways that root
cells can take up these ions from soil, either passively or actively. When a particular ion is in a
higher concentration in the soil than in the root hair cell, it will passively move
down its concentration gradient into the root, without requiring any extra input of
energy from the plant itself. This process is called
diffusion. The ion continues to passively
spread out by diffusion until there is an approximately equal concentration of this
particular ion in both areas.
Alternatively, if the concentration
of this ion is higher in the root hair cell than in the soil, as we can see in this
pink diagram on the right, then uptake of more of this particular ion must be done
actively. This process is called active
transport, and it requires an input of energy to move ions from an area of low to
high concentration into the root hair cell.
The question asks us to determine
what process is being shown by the movement of calcium ions in the diagram that is
provided to us by the question, shown on the far left. We can see that calcium ions, which
are represented as red circles, are in a far lower concentration in the soil than
they are in the root hair cell. As the arrows show calcium ions
moving into the root hair cell from the soil, from an area of low concentration to
an area of high concentration, we can work out the correct answer.
We know that moving particles from
an area of low to high concentration requires an input of energy so is an active
process. Therefore, the correct answer to
this question is active transport.
