Key difference: Pinocytosis is the absorption of liquids, whereas phagocytosis is the absorption of solid objects which are essentially food for the cell.

Both pinocytosis and phagocytosis are types of endocytosis. Endocytosis is a process by which cells absorb molecules by engulfing them. These molecules often include proteins and other substances which are important for the cell’s existence. The process of endocytosis is used by all cells as the molecules are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane.

Pinocytosis is the absorption of liquids, whereas phagocytosis is the absorption of solid objects which are essentially food for the cell. Almost all cells perform pinocytosis, however phagocytosis is performed only by specialized cells that protect tissues by engulfing bacteria, cell debris, and other abnormal materials.

Pinocytosis is essentially the process of absorbing fluid together with its contents into the cell. The cell does this by forming narrow channels through its membrane. These channels surround the liquid and all its contents and then pinch off into vesicles, hence the liquid in successfully absorbed into the cell. The molecules then fuse with lysosomes to hydrolyze or be broken down. The process of pinocytosis requires a lot of energy in the form of adenosine triphosphate. This is the chemical compound that is generally used as energy in most cells.

Phagocytosis is the process of absorbing and ingestion of particles by the cell and by many protests, such as amoeba to acquire nutrients. The absorption process is similar to pinocytosis, except that instead of liquid the absorbed substance are essential nutrients, which are surrounded by channel and then pinch off into vesicles. The nutrients are then fused with lysosomes and broken down by enzymes. Any and all waste material is then expelled from the cell.

Phagocytosis is synonymous with eating for single-celled organisms, however in multicellular animals, this process has been adapted to eliminate waste and debris, as opposed to taking in nutrients and fuel for cellular processes. This is especially the case for cells in the immune system which uses phagocytosis to remove pathogens and other cell debris, including but not limited to bacteria, dead tissue cells, and small mineral particles.

The substance absorbed by phagocytosis can be as large as the cell, which requires the cell to create vesicles big enough to surround the nutritents. However, in pinocytosis, the vesicles are much smaller, as they only need to surround liquids, which don’t have a specific shape. Technically, pinocytosis works as phagocytosis, the only difference being that phagocytosis is specific in the substances it transports. This is due to the fact that phagocytosis engulfs whole particles, which are later broken down by enzymes, and absorbed into the cells, whereas pinocytosis mainly absorbs already-dissolved or broken-down food.

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