singlemembrane

Singlemembrane refers to cellular compartments that are enclosed by a single phospholipid bilayer, in contrast to organelles bounded by two membranes. These compartments are part of the eukaryotic endomembrane system and participate in trafficking, processing, and storage of biomolecules. The membrane acts as a selective barrier, with proteins and lipids that regulate transport, lumen pH, and enzyme localization. Membranes continually remodel through vesicle budding, fusion, and lipid turnover, maintaining compartment identity while allowing exchange with the cytosol and other organelles.

Common singlemembrane organelles include lysosomes, endosomes, peroxisomes, Golgi apparatus, and vacuoles in plant and fungal cells. The endoplasmic reticulum forms an extensive single-membrane network that partakes in protein synthesis, lipid metabolism, and calcium storage; its lumen is topologically connected to the secretory pathway. The internal environments of these organelles are specialized (for example, acidic conditions in lysosomes) to support particular enzymatic activities and metabolic tasks.

Singlemembrane organelles contrast with double-membrane organelles such as mitochondria and chloroplasts, and with the nucleus, which have two surrounding membranes. Biogenesis typically involves vesicle trafficking from the endoplasmic reticulum and Golgi systems, along with targeted protein and lipid import to maintain organelle function. Dysfunction of singlemembrane compartments is implicated in several diseases, including lysosomal storage disorders and peroxisomal biogenesis disorders, highlighting their essential roles in cellular homeostasis and metabolism.