vacuoleslarge

Vacuoles large, or large vacuoles, are large membrane-bound compartments found in a variety of eukaryotic cells, most prominently in plants where a central vacuole can occupy a substantial portion of the cell volume. The term describes vacuoles that are disproportionately large relative to other vesicles within the cytoplasm.

Structure and formation: Vacuoles are bounded by a single membrane called the tonoplast in plant cells. They contain water and dissolved substances such as ions, sugars, organic acids, pigments, and waste compounds. Vacuoles originate from the endomembrane system and can form by fusion of vesicles or by growth and enlargement of preexisting vacuoles. The tonoplast houses transporters and proton pumps that help regulate osmotic balance and lumen pH, typically keeping the interior acidic.

Functions: In plants, the central vacuole stores water to maintain turgor pressure, contributing to cell rigidity and growth. It also sequesters ions, metabolites, pigments, and secondary compounds, and can compartmentalize toxic or waste substances. In addition to storage, vacuoles participate in degradation and recycling processes, often in concert with hydrolytic enzymes stored in related vacuolar compartments. In animal and fungal cells, vacuoles are generally smaller and diverse in function; lysosomes are a major type of degradative vacuole. Contractile vacuoles in some protists regulate water content by expelling excess fluid.

Size and variability: The size of vacuoles varies by cell type and species. Plant central vacuoles can occupy up to most of the cell’s volume in mature cells, while other vacuoles can be much smaller. The presence and prominence of large vacuoles reflect a role in osmoregulation, storage, and cellular homeostasis.

See also: Vacuole, Central vacuole, Tonoplast, Lysosome, Contractile vacuole.