Vacuoles
Vacuoles are surrounded by membranes. They are sort of like a storage bubble
in the cytoplasm. Vacuoles in animal cells are considerably smaller than
those in plant cells. In animal cells vacuoles may store food that needs
to be digested. Food cannot pass through membranes until it is broken into
smaller particles. The lysosome can fuse with the vacuole membrane and squirt
digestive enzymes into the food vacuole to break down what is in there.
Your white blood cells do this when they eat invading bacteria. Vacuoles
can also store the undigestible wastes until they can fuse with the cell
membrane and squirt the wastes outside.
Vacuoles in animal cells can form when the cell membrane surrounds a material
and pinches off to bring the substance inside the cell. This process is
called endocytosis.
Return to the animal cell
Plant Cell Vacuoles
The cell sap vacuole in plants is much larger than animals. In addition
to storing important substances, it also helps support the plant. The pressure
of water filling the cell sap vacuole pushes out against the cell wall.
This gives the wall enough strength to hold up fairly large gree (non-woody)
plants. We all know the first indication that we are not giving our house
plants enough water. They start to droop or wilt. Now you know why, so keep
that cell sap vacuole filled with water.
Return to the plant cell