Organelles found in plant cells, but NOT in animal cells
There are two main organelles, and one other structure, that are found in plant cells,
but not in animal cells. Some cells in Kingdom Protista also have these organelles, but
they are most closely associated with the cells from the Kingdom Plantae.
Plastids (specific example: chloroplasts)
There are a few different
types of organelles that fit into the category of "plastids," but the most
important type is the chloroplast; other types are mentioned below. All plastids are also thought to have evolved from endosymbiosis; they all have two
membranes around them and contain their own DNA and ribosomes within them. The inner
chloroplast membrane is highly folded, usually even more so than in mitochondria. This
inner membrane is jam-packed with the protein chlorophyll, and it is this pigment protein
that gives chloroplasts the capability of using the sunlight to make food. We have talked
about the fact that the organisms in the Kingdom Plantae are all autotrophic-- that is
because they contain chloroplasts which carry out photosynthesis. The chemical
reactions of photosynthesis all lead to the production of glucose. As a byproduct, the
chloroplasts also produce oxygen gas for our environment. So, you should be able to
recognize that photosynthesis and cellular respiration have some relation to one another.
In fact, the chemical reactions of photosynthesis are the reverse of those of cellular
respiration. The chloroplasts need water and carbon dioxide, and with the energy provided
by the sunlight, they are able to make those molecules into glucose and oxygen gas.
Do plant cells need to have both chloroplasts AND mitochondria? What do
you think?
Click on the question mark to see!
There are other plastids besides chloroplasts. In
the cell lab you get to see amyloplasts and chromoplasts. The prefix
"amyl-" stands for starch, while the prefix "chrom-" stands
for color. Therefore, amyloplasts are plastids that store starch, and
chromoplasts are plastids that contain pigment proteins. Amyloplasts are
found wherever plants need to save up their starch (like in the potato and
banana cells you view in lab). Chromoplasts are found in most locations
where plants take on a vibrant color (like in the red pepper cells you view in
lab, and also in flower petals). Plastids are obvious when viewing plant
cells that have them because they are large and membrane-bounded. They are
pretty cool.
Central/storage vacuole
This organelle is found inside of many plant cells
(pronounce it like vacuum with a final l instead of an m). It
stores water, and other small molecules, for later use by the cell. It can
also function like a lysosome for the plant cell.
Right after a rain, it
is easy for plants to acquire water. But if it has been a long time since a rain, because
plants are nonmotile and cannot just get up and walk over to the nearest pond, plants need
to have some way of still obtaining water. The storage vacuole lets them do just that.
In the cell lab using onion cells, you will see that when the storage vacuole empties, the cell shrinks (although the
cell wall does not). So,
if a plant is growing in the wild, and it has been a while since a rainfall, the cells
within that plant will shrink-- this also happens at home if you forget to water your
plants. What is the result of having many cells shrinking? The plant will wilt! It will
not get smaller as its cells shrink, because the cell walls are still there.
