Question

Pinocytosis was studied for the first time by
A) Metchnikoff
B) Lewis
C) Plowe
D) Nageli

Answer 1

Hint: Pinocytosis is also referred to as cell drinking or fluid endocytosis. The scientist who studied Pinocytosis for the first time was an American embryologist and cell biologist.

Complete Answer:
- The transportation of macromolecules like proteins, polynucleotides, fat droplets and polysaccharides etc. across the membrane takes place by endocytosis and exocytosis. Uptake of extracellular macromolecules by cells is called endocytosis, and secretion or release of macromolecules from the cells to the exterior is called exocytosis.

- Endocytosis involves invagination of plasma membrane and formation of membrane bound vesicles. This becomes possible because of the flexible and self-sealing nature of the plasma membrane. Endocytosis is generally involved in the ingestion of food material. . It is of two types – phagocytosis and pinocytosis. Intake of solid particles through endocytosis is called phagocytosis or cell eating and intake of liquid droplets by means of endocytosis is called pinocytosis or cell drinking.

- Phagocytosis is found in a large number of protozoa and among certain cells of metazoa. An amoeba ingests large food particles and microorganisms by this process. It is highly developed in granular leukocytes. Metchnikoff for the first time described phagocytosis.

- Pinocytosis involves the invagination of the plasma membrane to form a pocket, which then buds off inside the cell to form a vesicle filled with fluid. Such a vesicle is called a pinosome. The vesicle is then transported to other portions of the cell and fuses with lysosome or endosome. Absorption of fat droplets in humans is an important example of pinocytosis. Pinocytosis was first observed in 1931 by Warren Harmon Lewis in cultured cells and the term pinocytosis was also proposed by him.

Thus, the correct answer is B i.e., Lewis.

Note: Pinocytosis and phagocytosis are the methods of active transport because they require energy for their action.