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Eukaryotic Cells part I
Directions: Read and Highlight answering the questions as you go.
Think back to Schwann and Schleiden. It wasn’t until that fateful lunch that Schwann realized he was seeing
cells. After that moment cell biology knowledge exploded (just a saying; it didn’t really blow up). Once they
started piecing together the Cell Theory suddenly all living things were made of cells.
Even then, neither of these scientists realized how complex these cells really are. As modern scientists would
eventually discover, there are even smaller parts to this puzzle than just the cell.
As we discussed in class, the most common cell on earth is prokaryotic (bacteria). The one you are most
familiar with though is eukaryotic. It’s most familiar because it’s what you are. Everything we see and interact
with on a daily basis is eukaryotic from fish to humans to dogs and cats and birds and even mosquitoes. They
all have eukaryotic cells in their bodies.
Organelles
Within every eukaryotic cell are small organs called organelles. Organelles carry out many of the same
functions that your organs carry out. These structures perform various life processes that keep both the cell
and you alive. Interestingly, they complete many of the same process that your organs carry out such as
digestion, circulation, and even reproduction.
The following is a basic list of many of the organelles in both plants and animals.
Cell Wall
Even though there are only two different cells on earth, there are still differences between the same types of
cell. For example, prokaryotes have both eubacteria and archeabacteria. These two are as different as 6th
graders are to 8th graders (except for not having a nucleus. For eukaryotes though, the differences are more
subtle.
To help show these differences within eukaryotes,
let’s look at the two types of cells that we have
been exploring in class, animal cells and plant
cells. Let’s start with the outside of a eukaryotic
cell. Some eukaryotic cells have a stiff outside
structure called a cell wall. The cell wall acts like
the bricks on the outside of our school providing
extra support and helping everything stay upright.
Where all plants have a cell wall, no animal cells
have one.
As for their job, cell walls help a plant keep its shape. If they don’t hold enough water, the cell wall weakens
making a plant droop. While they do add some protection, the cell wall allows plants to grow to great heights.
Cell Membrane
Regardless of plant cell or animal cell, they all have a cell membrane. For plant
cells, the cell membrane is just inside the cell wall, but for animal cells the cell
membrane is the outer most covering. Remember, animal cells do not have a
cell wall .
The cell membrane is a soft protective layer that controls what comes in and out
of the cell. It’s kind of like the needle location on a soccer ball or a basketball. If
nothing pokes into it, the air is trapped inside. If you poke a needle into it, air
