vésicule

Vésicule is a term that designates a small sac enclosed by a membrane. In biology, vesicles are membrane-bound compartments within cells or at the cell surface that carry, store, or process various substances. In anatomy, the word can also refer to small bladder-like structures or organs, such as the vésicule biliaire (gallbladder) in vertebrates.

Structure and formation

Vesicles are typically spherical and bounded by a lipid bilayer. They form by budding from donor membranes, such as the endoplasmic reticulum, Golgi apparatus, or the plasma membrane, and they can fuse with target membranes to release their contents. Their internal milieu varies according to function, ranging from aqueous solutions to enzymes or signaling molecules.

Functions

Vesicles participate in intracellular trafficking, secretion, endocytosis, and digestion. They transport proteins and lipids between organelles, deliver cargo to the plasma membrane for secretion, and internalize material from outside the cell. In specialized cells, secretory vesicles store neurotransmitters or hormones until release. Lysosomes are vesicular organelles containing hydrolytic enzymes for degradation, while other vesicles handle storage and processing tasks.

Examples and diversity

Key types include transport vesicles that shuttle cargo between the ER and Golgi or from the Golgi to the plasma membrane; secretory vesicles in endocrine and exocrine cells; endocytic vesicles and endosomes formed during material uptake; and synaptic vesicles in neurons that release neurotransmitters. Plant cells contain large vacuoles that function as vesicular compartments, while various vesicles participate in immune and metabolic processes.

Clinical relevance

Disorders of vesicle trafficking and vesicle function are associated with numerous diseases, including lysosomal storage disorders and neurodegenerative conditions. Studying vesicles helps illuminate cellular transport, secretion, and metabolism.