Question Video: Recalling the Process of Water Movement into and Out of the Vacuole of a Plant Cell Biology

The diagram provided shows how cells can increase their turgidity. By what process does water move into the vacuole of the cell?


Video Transcript

The diagram provided shows how cells can increase their turgidity. By what process does water move into the vacuole of the cell?

Turgidity refers to the point at which the cell’s plasma membrane pushes against the cell wall, making the cell swollen and firm. In a plant cell, a state of high turgidity occurs when the vacuole is full of cell sap, which is a mix of water and dissolved solutes, like sugars and enzymes. The question asks us to give the process by which water moves into the vacuole. And for this to happen, water must first move into the cell.

Plants use a variety of mechanisms to transport materials in and out of their cells. And these mechanisms fall into two major categories: active transport and passive transport.

Passive transport moves substances from areas of higher concentration to lower concentration and does not require the input of cellular energy. An example of passive transport is diffusion, in which dissolved substances, or solutes, move across the plasma membrane from areas of higher concentration to areas of lower concentration. In the absence of active transport, diffusion will continue until both areas have approximately equal concentrations of the solute, a state known as equilibrium.

Sometimes the cell may need to maintain a higher solute concentration inside the cell than outside of the cell. This means the molecule in question has to move against its concentration gradient and against the natural tendency towards equilibrium. There are also times when molecules must be moved in or out of the cell but they are too large to cross the plasma membrane. In these cases, active transport mechanisms, which require cellular energy, will be used.

One example of active transport, called primary active transport, uses transmembrane enzymes powered by ATP to pump ions in and out of the cell against their concentration gradient. Luckily for plants and all living organisms, water does not require cellular energy to be moved in and out of cells. Instead, it is transported through a process called osmosis, which is similar to diffusion.

In osmosis, water molecules move from areas of lower solute concentration and higher water concentration to areas with higher solute concentration and lower water concentration. In other words, during osmosis, water molecules move towards equilibrium, just as nature likes it.

Plant cells can store large amounts of water in their vacuoles. So, when the concentration of water molecules is higher outside of the cell than inside of the cell, water will move through the process of osmosis into the vacuole of the cell.

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