Phagocytosis Pinocytosis detail presentation

Phagocytosis and pinocytosis are both processes by which cells take in substances from their environment, but they differ in the types of materials they ingest and the mechanisms involved.

Phagocytosis:
Phagocytosis is a cellular process in which specialized cells, such as macrophages and neutrophils, engulf and digest large particles or microorganisms, such as bacteria, viruses, or cellular debris. It involves the formation of pseudopodia (extensions of the cell membrane) around the target particle, enclosing it within a membrane-bound vesicle called a phagosome. The phagosome then fuses with lysosomes, forming a phagolysosome, where the engulfed material is degraded by enzymes. Phagocytosis plays a critical role in immune defense by clearing pathogens and debris from the body.

Pinocytosis:
Pinocytosis, also known as "cell drinking," is a non-specific cellular process in which cells take in fluid and dissolved substances from their surroundings by invaginating a portion of the cell membrane to form small vesicles called pinocytic vesicles. These vesicles contain the ingested fluid and substances and are internalized into the cell's cytoplasm. Pinocytosis occurs continuously in most cells and is involved in nutrient uptake, regulation of extracellular fluid composition, and sampling the extracellular environment. Unlike phagocytosis, pinocytosis does not involve specific recognition of target molecules and is not limited to particular types of particles.

In summary, phagocytosis is the engulfment and digestion of large particles or microorganisms by specialized cells, whereas pinocytosis is the non-specific uptake of fluid and dissolved substances by cells through invagination of the cell membrane. Both processes are essential for cellular function, nutrient acquisition, and immune defense.

1. Phagocytosis & Pinocytosis Nevil Dhaduk M.Sc.-Microbiology Parul University

2. What is Phagocytosis? It is defined as ingestion of particles of >0.5µm by cells .

3. Who Discovered Phagocytosis? Ellie Ilya Metchnikoff discovered it in 1882. Received Nobel prize for the same in 1906. Carl Fredrich Claus coined the term Phagocytosis.

4. Phagocytosis Phagocytosis : A mechanism by which cells engulf and carry particles into the cytoplasm Phagocytes : the white blood cells that protect the body by ingesting (phagocytosing) harmful foreign particles, bacteria, and dead or dying cells.

5. Phagocytic Cells: Macrophages (Monocytes), Neutrophils & Eosinophils (Macrophages) Professional and Non-professional phagocytes Professional phagocytes have receptors on their surfaces. can detect harmful objects Non-professional phagocytes Phagocytosis is not their principal function

6. The professional phagocytes include :- neutrophils Monocytes macrophages dendritic cells Mast cells. The non professional phagocytes include :- Fibroblasts phagocytose collagen in the process of remolding scars Osteoblasts

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8. Stages of Phagocytosis Chemotaxis Adherence Phagosome formation Digestion

9. Digestion/intracellular killing : P hagosome fuses with lysosome - phagolysosome. Lysosomal enzymes kill most bacteria within 30 minutes and include: Lysozyme: Destroys cell wall peptidoglycan Lipases and Proteases RNAses and DNAses lactoferrins, present in neutrophil granules and remove essential iron from bacteria. • After digestion, residual body with undigestable material is discharged.

10. Pinocytosis Pinocytosis is a type of endocytosis in which small particles suspended in the extracellular fluid are moved into the cell through pores formed on the cell membrane. The term pinocytosis is formed of two words “ pino ” and cytosis” where ‘Pino’ means “to drink” while ‘cytosis’ means relating to the cell. It is a continuous process in most cells and is a non-specific way for internalizing fluid and dissolved nutrients. The process of pinocytosis deals with the movement of a large number of tiny molecules through a fluid, which is why it is also called the fluid endocytosis or bulk-phase endocytosis. The molecules once inside the cells form vesicles which are then fused with the endosomes for the metabolic processes.

11. Process/ Steps of Pinocytosis The process of pinocytosis is initiated by the presence of the desired molecule in the extracellular fluid. The molecules, which acts as an inducer at this point, binds to the cell membrane triggering the initiation of the pinocytosis process. The molecules can be proteins, sugar, ions, or other molecules. In humans, pinocytosis is mostly associated with the absorption of fat. Although pinocytosis involves the binding of molecules to receptors in the cell membrane, it is different from other receptor-mediated endocytosis processes as the receptor is not specific for one molecule.

12. Types of Pinocytosis Pinocytosis is divided into categories on the basis of the size of the molecules to be transferred or on the basis of the mechanism of vesicle formation. On the basis of the size of the molecules, pinocytosis is of two types: Macropinocytosis In macropinocytosis, the molecules to be moved are rather large in size. The size of the vesicles formed might be about 1-2 µm in length. Micropinocytosis In micropinocytosis, the molecules to be moved are smaller in size. The size of the vesicles formed is about 0.1 µm in length.

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