The water tank of the cell
A big vacuole keeps plant cells firm.
A wilted plant
A plant looks fresh in the morning but droopy after a hot day without water. Water it, and it stands up again.
What inside the cells might change?
What this lesson covers
The idea
Mature plant cells have large central vacuoles of cell sap, within a selectively permeable membrane, storing water, minerals, sugars and wastes; their water pressure keeps the cell firm, so water loss wilts the plant; animal cells may have small vacuoles.
A wilted plant
A plant looks fresh in the morning but droopy after a hot day without water. Water it, and it stands up again.
What inside the cells might change?
- A big store of water in each cell
- The colour of the nucleus
- The cell wall disappears
Water the plant
Slide the soil water. Watch the vacuole and the plant.
Vacuoles
A mature plant cell usually has one large central vacuole, surrounded by a single selectively permeable membrane and filled with a watery fluid, the cell sap. It stores water, minerals, sugars and waste. The water pressure keeps the cell firm. When water is short, the vacuole loses water, cells become less firm, and the plant wilts. Animal cells may have small vacuoles for temporary storage.
A vacuole is surrounded by a single membrane and filled with cell sap.
- Plant cell | Animal cell
- Vacuole | one large central vacuole | small ones, sometimes
- Job | stores water, minerals, sugars, waste; keeps cell firm | temporary storage
Notes
A mature plant cell’s large central vacuole stores water, minerals, sugars and waste. Its water pressure keeps the cell firm; with too little water, the plant wilts.
Check yourself
What fills a plant vacuole?
Why does a plant wilt when it does not get enough water?
Which of these can a plant vacuole store?
Compared with plant cells, vacuoles in animal cells are…
- A watery fluid called cell sap — correct. Yes.
- Air. It holds watery cell sap.
- DNA. DNA is in the nucleus.
- Its vacuoles lose water, so cells become less firm — correct. Yes.
- Its cell walls dissolve. The walls stay.
- Its nuclei grow bigger. Not the reason.
- Water, minerals, sugars and waste material — correct. Yes.
- Only DNA. DNA is in the nucleus.
- Only light. It stores materials.
- sometimes present, smaller, and used for temporary storage — correct. Yes.
- always larger. They are smaller.
- never present. They are sometimes present.