I believe it is the cell membrane!
Animal Cells
Cholesterol is a substance that is found in animal cells but not in plant cells. It plays a key role in maintaining the structural integrity of cell membranes in animals.
there are cells in the animals hair
A cell wall.
The cell wall is located just outside the cell membrane of plant cells. The cell wall is made of a substance called cellulose and is not found in animal cells.
A leaf
Plant cells have a cell wall around the outside, but animal cells only have a cell membrane.
cell walls are in plant cells outside of the membrane, while animal cells don't have a wall, only a membrane.
cell wall
protoplasm
The outside covering that all plant cells have and that is not found in animal cells is called a cell wall. The cell wall provides structure, support, and protection to the plant cell, allowing it to maintain its shape and resist mechanical stress.
The outside "shell" of a animal or plant shell actually differ. Plant cells have two outer coverings, they have a cell wall and a cell membrane. Animal cells have only a cell membrane.