Question

Define phagocytosis or endocytosis or pinocytosis?

Answer 1

Hint:-Organisms need a certain mechanism to ensure their survival by adopting some defense activity against the intracellular pathogens as well as any harmful elements invading the body. In some processes, the cell organelles may help destroy pathogenic agents or particles either by breaking into segments or by direct engulfment of pathogenic agents.

Complete Answer:-Endocytosis is the process by which eukaryotes engulf materials from their surrounding with the help of membrane-bound vesicles at the cell surface. It is then followed by pinching-off and release of free vesicles into the cytoplasm. Endocytosis is broadly divided into Phagocytosis (cell-eating) and pinocytosis (cellular drinking). Phagocytosis or cell-eating is the internalization of large particles following particle binding to specific plasma membrane receptors, and by the formation of large endocytic vesicles called phagosomes. The phagosomes fuse with lysosomes to form phagolysosomes.
In protozoans, phagocytosis is a process by which they obtain nutrition where large particles are taken up by the phagosomes which then end up in lysosomes. In multicellular eukaryotes, few specialized cells perform phagocytosis but for the non-nutritive process. In mammals, two types of WBC – macrophages and neutrophils perform professional phagocytosis that helps in the defense mechanism of the body.
Phagocytosis is an active process that is actin-mediated, and involves highly specific cell surface receptors in addition to the signaling cascades. Pinocytosis, on the other hand, is the process of ingestion of fluid by the formation of small vesicles.

Note:- Large molecules are carried into the cell with the assistance of membrane-bound vesicles. These vesicles are derived by invagination and pinching-off of pieces of the cell membrane by the method of endocytosis. Cells adopt these sorts of self-defense mechanisms to protect itself from any sort of damage or destruction affecting cellular metabolism.