Download Cell Wall • Like animal cells, plant cells contain a cell membrane

Cell Wall and Vacuoles | MCAT 2015
Cell Wall
• Like animal cells, plant cells
contain a cell membrane, which:
o Provides a barrier
between the cell and the
environment
o Facilitates transport
• Unlike animal cells, plant cells
contain a cell wall
o Typically several hundred
times thicker than the cell
membrane
•
o It may account for ¾ of
the cell’s volume
The central vacuole:
o Stores water and food
o Stores waste products
o Stores digestive enzymes
o Regulates cell acidity
By absorbing H+
from cytoplasm
Central Vacuole
The central vacuole is a storage vessel that
accounts for a tremendous portion of the plant
cell’s volume.
•
Plant Cell
Plant cells contain a cell wall (thick green).
Although not drawn to scale here, the cell wall is
typically several hundred times thicker than the
cell membrane.
•
•
The cell wall is constructed from
the polysaccharide cellulose
It serves to offer the cell:
o Strength
o Protection
o Structure
Consider the rigid
stem of a flower
•
Flower Stem
The rigid cell wall is so durable that the stem
doesn’t buckle under the weight of the flower.
Since plants are immobile, they
must have these huge reservoirs
to stock up on water/nutrients
when they are available
o They must stay nourished
in the event of a shortage
In the event of a drought, the cell
will utilize its water reserves
o As this occurs, the turgor
pressure in the cell wall
decreases, and the cell
wall loses its rigidty
Draining of the Central Vacuole
When the water reserves of the central vacuole
are expended, turgor pressure on the cell wall is
diminished, and the plant appears to wilt.
Vacuoles
• Plant cells (like other cells)
contain storage compartments
called vacuoles
• But plant cells contain a gigantic
central vacuole
•
When water becomes available,
the central vacuole is
replenished, and the cell can
regain its structure
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