Question

Why is endocytosis found in animals only?
A. Cell wall is absent in animal cells.
B. Cell wall is present in animal cells.
C. Cell membrane is absent in animal cells.
D. None of these

Answer 1

Hint: The word ‘endo’ means inside and the word ‘cytosis’ means the moment of molecules across the cell membrane. For endocytosis to occur the cell membrane needs to be directly in contact with the external environment for free movement of molecules across the membrane.

Complete step by step answer:
Endocytosis is a process where a cell engulfs or takes in molecules from the surrounding external medium. The nature of the cell membrane is hydrophobic and that is why the polar or big molecules cannot pass through it. This mechanism is usually used to take in food particles. These molecules are engulfed and stored in temporary storage units called vesicles. These serve as an external covering which is later removed once the vesicle is taken inside the cell. It breaks open releasing the particle inside. For this process to occur, the cell membrane needs to be directly in contact with the surrounding environment. In a plant cell, the cell membrane is protected by another layer, the cell wall. Which breaks the contact of the cell membrane and the surrounding environment. So this process cannot take place inside a plant cell. In the case of animal cells, as we know, the cell wall is absent in it and thus endocytosis can easily take place as the cell membrane is directly in contact with the surrounding. So, the absence of a cell wall actually makes endocytosis possible only in those cells which lack a cell wall.
Hence, the correct answer is option A, i.e.,cell wall is absent in animal cells.

Additional information: The mechanism of endocytosis is used by cells of the immune system to engulf microbes and pathogens and kill them. It is also majorly used by protists to engulf food particles which are generally polar and big in size.

Note: One of the unique characteristics of animal cells is the lack of cell wall which enables them to perform endocytosis. And possessing a cell wall is the reason plants cannot perform it.