Intracellular transport

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Intracellular transport is the movement of vesicles and substances within a cell. Intracellular transport is required for maintaining homeostasis within the cell by responding to physiological signals.^[1] Proteins synthesized in the cytosol are distributed to their respective organelles, according to their specific amino acid’s sorting sequence.^[2] Eukaryotic cells transport packets of components to particular intracellular locations by attaching them to molecular motors that haul them along microtubules and actin filaments. Since intracellular transport heavily relies on microtubules for movement, the components of the cytoskeleton play a vital role in trafficking vesicles between organelles and the plasma membrane by providing mechanical support. Through this pathway, it is possible to facilitate the movement of essential molecules such as membrane‐bounded vesicles and organelles, mRNA, and chromosomes.

Intracellular transport is unique to eukaryotic cells because they possess organelles enclosed in membranes that need to be mediated for exchange of cargo to take place.^[3] Conversely, in prokaryotic cells, there is no need for this specialized transport mechanism because there are no membranous organelles and compartments to traffic between. Prokaryotes are able to subsist by allowing materials to enter the cell via simple diffusion. Intracellular transport is more specialized than diffusion; it is a multifaceted process which utilizes transport vesicles. Transport vesicles are small structures within the cell consisting of a fluid enclosed by a lipid bilayer that hold cargo. These vesicles will typically execute cargo loading and vesicle budding, vesicle transport, the binding of the vesicle to a target membrane and the fusion of the vesicle membranes to target membrane. To ensure that these vesicles embark in the right direction and to further organize the cell, special motor proteins attach to cargo-filled vesicles and carry them along the cytoskeleton. For example, they have to ensure that lysosomal enzymes are transferred specifically to the golgi apparatus and not to another part of the cell which could lead to deleterious effects.