top of page


  • Large particles cannot cross the cell membrane → they enter the cell by endocytosis.

  • Types of endocytosis:

    • Pinocytosis

    • Phagocytosis


  • Means drinking by the cell.

  • for intake of macromolecules.

  • Occur continuously in most cells.

Cell expresses receptors on cell membrane for molecules that it wants to take in

These receptors are located on coated pits

The molecule binds the receptors

Proteins underneath the pit pull the membrane inside the cell & ...

break the mouth of the pit

Formation of vesicle inside the cell containing the molecule and extracellular fluid

Vesicle formed by pinocytosis is called pinocytotic vesicle. These vesicles are very small.

  • This process required energy from ATPs.


  • Means eating by cell.

  • for intake of larger particles like bacteria, whole cell etc.

  • Only some cells have capacity for phagocytosis e.g. tissue macrophage.

  • Mechanism of phagocytosis is similar to pinocytosis.

Som ligand on the particle to be ingested binds with the cell surface receptor

Membrane around this attachment evaginates to cover the particle

the membrane merges on the other side

forms vesicle inside the cell

Vesicle formed by phagocytosis is called phagocytic vesicle. It's large.

Digestion of Ingested Material

The vesicle formed by pinocytosis/phagocytosis merges with lysosome

Lysosome empties its hydrolase enzymes in the vesicle

Now the vesicle is called digestive vesicle

Hydrolase enzymes break down the ingested particles

1. Smaller molecules like amino acid, glucose, etc → cross the membrane of vesicle → enter the cytoplasm.

2. Indigestible material is left inside the vesicle → excreted out of the cell by exocytosis.


Next >>


bottom of page