What does bulk transport refer to?

Bulk transport refers to the movement of large molecules and particles across the plasma membrane of a cell. This process is essential for the uptake of substances that are too large to pass through the membrane via simple diffusion or through protein channels. Bulk transport includes mechanisms such as endocytosis, where the cell engulfs large molecules or particles, and exocytosis, where substances are expelled from the cell.

In contrast to bulk transport, the movement of small ions across the membrane, processes like osmosis, and the diffusion of gases in cellular respiration all pertain to distinct forms of transport that typically involve smaller and more permeable substances. These processes do not encompass the same scale or mechanisms as bulk transport, highlighting the uniqueness of the transport of larger entities.