Final answer:
Phagocytosis is a cellular process where a cell engulfs large particles, which is essential for immune function, while pinocytosis allows a cell to ingest dissolved substances in the extracellular fluid. Both are forms of endocytosis, requiring energy in the form of ATP, and involve the membrane forming a vesicle around the substance to be absorbed.
Step-by-step explanation:
Phagocytosis and Endocytosis
Phagocytosis, often described as "cell eating," is a form of endocytosis where a cell engulfs large particles such as other cells, macromolecules, or cell fragments from the extracellular fluid. This is an essential process for immune cells, like white blood cells, to eliminate pathogens. Pinocytosis, or "cell drinking," is another form of endocytosis where cells ingest extracellular fluid containing dissolved substances through small vesicles. Both processes involve active transport and the direct use of ATP, as the plasma membrane invaginates to form a pocket around the particle, which then pinches off into a vesicle within the cytoplasm.
The Process of Phagocytosis
In phagocytosis, phagocytes extend pseudopodia to surround and engulf the target particle. Once inside the cell, a lysosome fuses with the phagosome to digest the engulfed particle. This is crucial for defending the body against invaders such as bacteria and other foreign particles.
On the other hand, pinocytosis involves the folding of the plasma membrane to allow dissolved substances into the cell, forming a pinocytic vesicle which then releases its contents into the cytoplasm.