Pinocytosis vs. Phagocytosis

Key difference

The key difference between phagocytosis and pinocytosis is that phagocytosis denotes for “cellular eating” mostly engulfing a solid substance while pinocytosis denotes for “cellular drinking,” mostly engulfing liquid substances.

Phagocytosis vs. Pinocytosis
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Phagocytosis and pinocytosis both are types of endocytosis which refer to the ‘intake of materials by the cell membrane.’  When a cell intakes the solid particles with vesicles formation, it is called as phagocytosis while when a cell intakes liquid substances by vesicle formation, it is termed as pinocytosis. Vesicles formed during the process of phagocytosis are called as phagosomes while vesicles formed during the process of pinocytosis are called as pinosomes. Simply speaking, phagocytosis is the “cellular eating” of something while pinocytosis is “cellular drinking” of something.

The process of phagocytosis occurs by the pseudopodia (false feet) which are the projections of plasma membrane formed at the time of engulfing. The process of pinocytosis takes place by the process of invagination.

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The process of phagocytosis is substrate specific. Only that solid particles are engulfed by the cell which is of a special type. While the process of pinocytosis is not substrate specific. A cell has the ability to take all kinds of fluid present in its surrounding.

Phagocytosis is a sort of protective mechanism. It can be considered as a defense mechanism. The cell eats a foreign body when it founds that body in its surrounding. Pinocytosis is used simply for the intake of liquids.

When phagosomes are formed during the engulfing of solid particles by cell, lysosomes unites with phagosomes to form food vacuoles. Lysosomal enzymes are mandatory for the digestion of these solid particles. There is no role of lysosomes when a pinosomes are formed during the intake of liquid by the cell. This is so because no enzymes are needed for the digestion of liquid material.

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Particles engulfed by the cell in the process of phagocytosis are harmful bacteria, foreign bodies, virus, and dust, etc. Particles which the cell takes during pinocytosis are sugars, amino acids, ions, enzymes, and hormones, etc.

Types of cells in which phagocytosis occurs are macrophages, neutrophils, and protozoans. Pinocytosis takes place usually in cell linings of blood capillaries and in secretory cells.

Both phagocytosis and pinocytosis are active processes and require energy in the form of ATP for the intake of materials.

During phagocytosis, engulfed substances are further broken down in the smaller particles while during pinocytosis, no further break down of the materials occurs.

Comparison chart

Basis Phagocytosis Pinocytosis
Definition Phagocytosis is a process in which a cell engulfs the solid particles. Pinocytosis is a process in which the cell takes the liquid particles.
Types of vesicles formed Vesicles formed during this process are called phagosomes. Vesicles formed during this process are called pinosomes.
Need for lysosomal enzymes Lysosomes combine with phagosomes for further break down of the particles. Lysosomes do not unite with pinosomes.
Requirement of energy It is an active process. Energy is mandatory in the form of ATP. It is an active process. Energy is mandatory in the form of ATP.
Types of particles engulfed Particles engulfed during this process are harmful bacteria, viruses, dust particles, and foreign bodies, etc. Particles taken by the cell during this process are sugars, amino acids, enzymes, hormones, ions or any other liquid particles.
Process occurs by Phagocytosis occurs by the formation of pseudopodia (false feet) by the cell. Pinocytosis takes place by the process of invagination of the cell membrane.
Specificity of substrate This process is substrate specific. Only specific solids are engulfed by the cell. This process is not substrate specific. Any liquid can be taken by the cell.
In which types of cells, it takes place This occurs in macrophages, neutrophils, and protozoans. This occurs in the cell lining of blood capillaries and secretory cells.
Type of mechanism It is a protective mechanism. It is simply the intake of liquid particles.
Breakdown of the engulfed material A further breakdown of the engulfed particles is mandatory in this process otherwise digestion of that particles does not occur. A further breakdown of the particles is not required. Digestion of that substances takes place easily without breaking.

What is phagocytosis?

Phagocytosis is a process during which a cell engulfs the solid particles. That is why it is also called as “cellular eating” of something. When a cell engulfs a solid material, a vesicle is formed called as phagosome. It is, in fact, the invagination of the cellular membrane which contains the engulfed particles in it. After the formation of the phagosome, lysosome is attached to it, and this complex of phagosome and lysosome is called as phagolysosome. This happens because lysosomal enzymes are needed for the breakdown of the engulfed solid particles into smaller ones otherwise they cannot be absorbed by the cell. Phagocytosis is the further classification of endocytosis, a process during which a cell takes in it some material[f1]  from outside. It an active mechanism. Energy is required in the form of ATP. Phagocytosis occurs in many types of cells among which macrophages, neutrophils, and protozoal cells are remarkable. It is a sort of protective mechanism by which cells engulf the harmful bacteria, viruses, dust particles, and other foreign substances.

What is pinocytosis?

Pinocytosis a process during which a cell intakes some liquid material. It is also a type of endocytosis. This process is not substrate specific. A cell can take inside any liquid material present in its surroundings. That is why pinocytosis is also called as “cellular drinking of anything.” One thing must be remembered that besides liquids if a cell engulfs very tiny solid particles which are not required to be digested by lysosomal enzymes, it is also pinocytosis. This is so because lysosomal attachment is mandatory for phagocytosis but not for pinocytosis. Particles taken by the cell during pinocytosis are simply absorbed by the cell and do not need any additional enzymes.

Pinocytosis is also an active process. Energy is mandatory in the form of ATP. Enzymes, hormones, ions, small sugar molecules, and liquid substances are taken by the cell during this process. Vesicles are formed which are termed as pinosomes. Mostly pinocytosis occurs in the lining cells of blood capillaries and secretory cells.

Key differences

  1. Phagocytosis is the engulfment of the solid particles by the cell while pinocytosis is the process during which a cell takes in any liquid particles.
  2. Phagocytosis occurs in neutrophils, macrophages, and protozoal cells while pinocytosis occurs in the lining cells of blood capillaries and secretory cells.
  3. Phagocytosis occurs by the formation of pseudopodia by the cell membrane while pinocytosis occurs by the invagination of the cell membrane.
  4. During phagocytosis, a further breakdown of the engulfed material takes place by lysosome while in pinocytosis, no further breakdown occurs.
  5. Phagocytosis is specific according to the type of substrate while pinocytosis is not specific.

Conclusion

Phagocytosis and pinocytosis are the commonly used terms in biology. Since both are the types of endocytosis during which a cell takes inside the external substances, they are often mixed by the students. It is compulsive to know the difference between both of them. In the above article, we learned the clear differences between phagocytosis and pinocytosis.

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