Peroxisomes are small (0.1–1 µm diameter) subcellular compartments (organelles) with a fine, granular matrix and surrounded by a single biomembrane which are located in the cytoplasm of a cell. Compartmentalization creates an optimized environment to promote various metabolic reactions within peroxisomes required to sustain cellular functions and viability of the organism.
The number, size and protein composition of peroxisomes are variable and depend on cell type and environmental conditions. For example, in bakers yeast (S. cerevisiae'), it has been observed that, with good glucose supply, only a few, small peroxisomes are present. In contrast, when the yeasts were supplied with long-chain fatty acids as sole carbon source up to 20 to 25 large peroxisomes can be formed.