Download PROKARYOTIC AND EUKARYOTIC CELLS

PROKARYOTIC AND EUKARYOTIC CELLS
All living organisms on Earth are divided into cells. The main concept of cell theory is that cells are the basic structural unit
for all organisms. Cells are small compartments that hold the biological equipment necessary to keep an organism alive and
successful. Living things may be single-celled or they may be very complex such as a human being.
The first cells to appear on Earth were prokaryotic cells. A prokaryote is an organism made of a single prokaryotic cell also
called single-celled organisms. The earliest prokaryotes may have arisen more than 2.5 billion years ago. “Pro” means
“before” and “karyon” means “nucleus”. So, prokaryote means “before a nucleus”. Prokaryotes fall into two major
categories: Kingdom Eubacteria (“true bacteria”) and Kingdom Archaeabacteria (“ancient bacteria”). Eubacteria are
common types that occur all around us, usually on surfaces and in the soil. You can only find Archaeabacteria in extreme
environments, like hot sulfur springs.
They are very small cells with a simple structure and contain no membrane bound organelles. Prokaryotes do not have a
nucleus. Instead, prokaryotes have a nucleoid region that contains the DNA that floats in the cell’s cytoplasm. Proteinmaking bodies called ribosomes are also within the cytoplasm. Like all cells, prokaryotes have a cell membrane. All
prokaryotes also have a cell wall surrounding the cell membrane. The cell wall helps provide support and protection for the
cell. Some prokaryotes are enclosed by an additional layer called the capsule. The capsule has a sticky surface area, so it allows
prokaryotes to cling to surfaces, such as your skin and your teeth. Pili (pilus) are hair-like structures on the surface of the cell
that attach to other bacterial cells. Shorter pili called fimbriae help bacteria attach to surfaces. Flagella (flagellum) are long,
whip-like protrusion that aids in cellular locomotion.
Directions: From the reading, answer the following questions.
1. What does prokaryote mean?
2. What are examples of prokaryotes?
3. Color and label the prokaryotic cell below.
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1. The three bacterial shapes in Model 1 are referred to as coccus (sphere), spirillum, and bacillus (rod). Label the
diagrams in Model 1 with the correct descriptions.
2. What is represented by the small dots found in each of the bacteria cells?
3. What is the name of the outermost layer that forms a boundary around the outside of each cell?
4. How is the DNA described and what does this mean?
5. All the internal structures are suspended (floating) in what substance?
6. One of the bacteria in Model 1 has a tail-like structure.
a. What is this structure called?
b. What might be the purpose of this structure?
c. Based on your answer to the previous question, what might you infer about the absence of this structure in the other two
bacteria cells?
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Eukaryotic cells are more complex than prokaryotic cells. “Eu” means “true” and “karyon” means “nucleus”. So,
eukaryote means “true nucleus”. Examples of eukaryotes are protists, fungi, plants, and animals.
They all have a cell membrane, ribosomes, and DNA as prokaryotic cells do. However, the DNA of eukaryotic
cells does not float freely in the cytoplasm. Instead, it is found in the nucleus, an internal compartment bound by
a cell membrane. The nucleus is one kind of organelle found in eukaryotic cells. Organelles are structures that
perform specific functions. Most organelles are surrounded by a membrane. Some organelles have membranes
that form channels, which help transport substances from one part of the cell to another part of the cell.
Eukaryotes are organisms made of one or more eukaryotic cells. The earliest eukaryotes, like the first
prokaryotes, were single-celled organisms. They arose about 1 billion years later than the earliest prokaryotes.
Later, multicellular eukaryotes arose. Every type of multicellular organism that exists is made up of eukaryotic
cells.
1. What does eukaryotic mean?
2. Looking at Model 2, list at least three structural differences (other than shape) between an animal and a
plant cell.
3. Where do you find the DNA in each cell in Model 2?
4. Do both cells in Model 2 have a nucleus?
5. List the structure(s) that form the boundary between the inside and the outside of each cell in Model 2.
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6. What is different about the outermost boundary in a plant cell compared to an animal cell?
7. Decide as a group whether the cells in Model 1 or 2 are more complex and list at least three supporting
reasons for your choice.
1. By comparing Model 1 and Model 2, what structures are the same in both prokaryotic and eukaryotic cells?
2. Draw a Venn diagram showing the differences and similarities between a prokaryotic and eukaryotic cell?
3. Refer to Models 1 and 2 to complete the chart below. Write yes or no in the box for each cell.
Bacterial Cell
Plant Cell
Animal Cell
All Cells
Cell Membrane
Ribosome
Cytoplasm
Mitochondria
Nucleolus
Nucleus
DNA
Cell Wall
Prokaryotic
Eukaryotic
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1. As a group, write a definition for a prokaryotic cell.
2. As a group, write a definition for a eukaryotic cell.
An efficiency apartment is a one-room apartment. This one room is where you sleep, eat, shower, and entertain
your guests. It all happens in one room. It is a simple way of living in a small space. A mansion is a large, complex
living space with many separate rooms. There are rooms for cooking, eating, sleeping, bathing, reading, watching
TV, entertaining guests, exercising, and storage. The rooms in a mansion are constructed for the specific things you
would like to be able to do. You can live in simple efficiency or complexity. In this activity we will be looking at
cells that are as simple as a one-room efficiency apartment or as complex as a mansion.
3. As a group, discuss the analogy above of an efficiency apartment and a mansion as it relates to cells. Record
your final consensus of how this analogy applies to cell structure.
1. What effect do you expect the structural differences between prokaryotes and eukaryotes to have on their
functions? Explain in detail.
2. With as much detail as possible, give another example of an analogy for describing the difference between
prokaryotic cells and eukaryotic cells.
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