It's not entirely accurate to say that microvilli are only possible in animal cells. While microvilli are more common and prominent in animal cells, they are also found in plant cells, albeit with some important differences.

Here's a breakdown:

Microvilli in Animal Cells:

* Function: Primarily increase surface area for absorption, particularly in the digestive system and kidneys.

* Structure: Finger-like projections of the cell membrane, supported by a core of actin filaments. This structure gives them flexibility and allows them to move slightly.

* Abundance: More numerous and densely packed compared to plant cells.

Microvilli in Plant Cells:

* Function: Less well-understood but may play a role in nutrient absorption and cell-cell communication.

* Structure: Shorter and less numerous, often associated with the cell wall. While they may have an actin core, it is less organized and pronounced.

* Abundance: Less frequent and less well-defined compared to animal cells.

Key Differences:

* Cell Wall: The rigid cell wall in plants limits the flexibility and movement of the cell membrane, which restricts the formation of long, flexible microvilli like those seen in animal cells.

* Metabolic Pathways: Plant cells have different metabolic pathways than animal cells, and the need for increased surface area for absorption is not as prominent in many plant tissues.

* Adaptations: Animal cells have evolved specific adaptations for absorption, such as the highly developed microvilli in the intestinal lining, which are not as essential in plants.

Therefore, while microvilli are more prominent and play a more prominent role in animal cells, they are not entirely absent in plant cells. Their function and structure may differ, but they are still a feature of both types of cells.