Vacuole and Tonoplast: Function in Plant and Animal Cells
Biology · Cell: The Unit of Life · NEET
A vacuole is a membrane-bound space in the cytoplasm that stores water, cell sap, and waste. Its single covering membrane is called the tonoplast. Plant cells have one large central vacuole (up to 90% of the cell), while animal cells have only small or no vacuoles. Memory hook: "TONO wraps the vacuole, ONE membrane only."
The plant central vacuole fills most of the cell and is wrapped by a single membrane, the tonoplast, which actively pumps ions inside; the vacuole has no DNA and is largely absent in animal cells.
Your doubts, answered
Is a vacuole present in animal cells or only plant cells?
Both can have vacuoles, but they are different. Plant cells have ONE big central vacuole that can fill up to 90% of the cell. Animal cells have only small vacuoles, or sometimes none. NCERT says the large central vacuole is a plant feature that is absent in animal cells. NEET traps you by pairing 'large central vacuole' with 'animal cells' - that is wrong.
What is the tonoplast and how many membranes cover a vacuole?
The tonoplast is the single membrane that surrounds the vacuole. A vacuole is bound by only ONE membrane. This is important: mitochondria and chloroplasts have two membranes, but the vacuole has just one. So do lysosomes. Remember: tonoplast = one membrane = the vacuole's wall.
Does a vacuole contain DNA?
No. A vacuole does NOT contain DNA. Only mitochondria, chloroplasts (semi-autonomous organelles), and the nucleus have DNA. Lysosomes and vacuoles have no DNA. NEET 2019 asked exactly this: the pair with no DNA is lysosomes and vacuoles.
What is the difference between a central vacuole, a contractile vacuole, and a food vacuole?
A central vacuole is the large storage vacuole in plant cells that holds cell sap, ions, and waste. A contractile vacuole is found in Amoeba and does osmoregulation and excretion (it pumps out extra water). A food vacuole forms in protists like Amoeba by engulfing food particles for digestion. Same word 'vacuole' but three different jobs.
Why can the plant vacuole occupy up to 90% of the cell?
The plant vacuole fills with water and cell sap and pushes the cytoplasm and organelles to the edge. This creates turgor pressure that keeps the plant cell firm and helps the cell grow larger without making more cytoplasm. Because it is so big, it stores water, ions, and waste efficiently.
What does the tonoplast do besides covering the vacuole?
The tonoplast is an active transporter. In plants it moves ions and other materials AGAINST their concentration gradient into the vacuole. That is why the concentration of these substances is much higher inside the vacuole than in the surrounding cytoplasm. This uses energy - it is active transport, not simple diffusion.
⚠️ The NEET trap ✗ Large central vacuoles are a feature of animal cells. ✓ Large central vacuoles are a feature of PLANT cells; they are absent in animal cells (animal cells have small vacuoles or none). 🧠 If a match statement says 'large central vacuole - animal cell', it is the MISMATCH. Central vacuole = plant, always.
Real NEET questions
NEET 2016
Water soluble pigments found in plant cell vacuoles are:
A · Xanthophylls
B · Chlorophylls
C · Carotenoids
D · Anthocyanins ✓
Solution: Anthocyanins are water-soluble pigments that dissolve in the cell sap inside plant vacuoles, giving red, purple and blue colours to flowers and fruits. Xanthophylls, chlorophylls and carotenoids are fat-soluble pigments located in plastids, not in the vacuole. So the vacuole pigment is anthocyanin.
NEET 2017
Select the mismatch.
A · Gas vacuoles - Green bacteria
B · Large central vacuoles - Animal cells ✓
C · Protists - Eukaryotes
D · Methanogens - Prokaryotes
Solution: Large central vacuoles are a feature of PLANT cells, not animal cells - NCERT states the large central vacuole is absent in animal cells. Gas vacuoles do belong to green bacteria, protists are eukaryotes, and methanogens are prokaryotes, so those are correct matches. The mismatch is B.
NEET 2019
Which of the following pair of organelles does not contain DNA?
A · Mitochondria and Lysosomes
B · Chloroplast and Vacuoles
C · Lysosomes and Vacuoles ✓
D · Nuclear envelope and Mitochondria
Solution: Lysosomes and vacuoles do not contain DNA. Mitochondria and chloroplasts have their own circular DNA, and the nucleus (bounded by the nuclear envelope) holds chromosomal DNA. So the only pair with NO DNA is lysosomes and vacuoles.
Solved Cell: The Unit of Life NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The tonoplast. It is a single membrane that surrounds the vacuole.
How much of a plant cell can the vacuole fill?
In plant cells the vacuole can occupy up to 90 per cent of the cell volume.
What is stored in a vacuole?
Water, cell sap, excretory products, ions, and other materials not useful to the cell. In some plants it also holds water-soluble pigments like anthocyanins.
What is the function of a contractile vacuole?
In Amoeba, the contractile vacuole carries out osmoregulation and excretion by removing extra water from the cell.
Is the vacuole part of the endomembrane system?
Yes. The endomembrane system includes the endoplasmic reticulum, Golgi complex, lysosomes and vacuoles because their functions are coordinated.
