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Eukaryotic Cells
Name:______________________
Directions: Read, Highlight, and answer the questions!
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. 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 can be pumped inside. The cell
membrane is very similar to this opening. The role of the cell membrane
is to hold all of the organelles and fluids (cytoplasm) inside the cell and
keep some nasty things such as bacteria outside the cell.
Cytoplasm
Inside the nucleus is a fluid called the cytoplasm (siet oh plas um) that keeps all the organelles from bumping
into each other. (Think of a swimming pool filled with children during summer. The water is the cytoplasm and the
children are the cell organelles). The cytoplasm also helps the cell membrane keep its shape (kind of like water inside
a water balloon).
Nucleus
All Eukaryotic cells have a nucleus. Remember looking at the onion and cheek cells and seeing the darker
spot inside the cell, well that is the nucleus. The nucleus is like the brain of the cell, it controls all cell activities.
Inside the nucleus are the Chromosomes
or genetic material. The chromosomes contain
information for the cell’s job or function.
Chromosomes are made up of DNA which stands
for Deoxyribonucleic acid (Wow what a mouth
full). The chromosomes send out messages to
other organelles in the cell, telling them what to
do. Without your chromosomes, you wouldn’t
have hair color, eye color, a nose, mouth, well you get the picture.
The darker spot inside the nucleus is the nucleolus. If we had a more powerful microscope it would kind of look
like an eye inside the nucleus. This organelle is responsible for making ribosomes, but we will discuss those next.
1. If the most common cell is prokaryotic, why do people believe that eukaryotic cells are more common?
2. What is the purpose of the cell wall?
a.
b.
c.
d.
To make a plant droop.
To support the cell
To carry DNA
To digest cellulose.
3. What organelle does a plant cell have that an animal cell does not? _____________________________
4. What is the purpose of a cell membrane?
a. To make lipids
b. To make phospholipids
c. To protect the cell
d. To support the cell wall
5. What is the genetic material inside a cell’s nucleus?
a.
b.
c.
d.
Protein
Lipids (fats)
Chromosomes (DNA)
Nucleolus