Cell Biology

 
                                               
       
       
       
       
       
       
       
       
                                       
 

Exercise 1:  Features of Prokaryotic Cells

             Because we will study the prokaryotes in more detail at a later date, we will look at only one prepared slide of a prokaryotic organism, a species of bacteria in the genus Anabaena.  Bacteria in this genus typically have a second (outer) membrane impregnated with lipopolysaccharide and lipoprotein molecules.  This is sometimes referred to as a mucilaginous or mucous sheath and makes these bacteria feel “slimy.”  Refer to the micrograph of Anabaena on the last page of this handout and note the starch grains, thylakoid membranes (where photosynthesis takes place), mucous sheath, and cell wall.

 Materials:
            Microscope
            Prepared slide of Anabaena

 

Procedure:
 1. Observe Anabaena under your highest magnification.

 Questions:
1. Draw a few cells of Anabaena.  Are nuclei visible in the cells of Anabaena?
2. Can you see any of the structures on your slide that are indicated on the micrograph?  Why not?
3. Can you detect the mucous sheath of Anabaena with your microscope?  

Exercise 2:  Features of Unicellular Eukaryotic Cells

             The following procedures will allow you to observe some simple eukaryotic cells.  Compare these cells to the prokaryotic cells and to the more complex animal and plant cells.

 Materials:
            Microscope
            Euglena
            Paramecium
            Amoeba

Procedure:
1. Observe each organism at various levels of magnification and answer the following questions.

Questions:
1. Can you see a nucleus?

 2. What is unusual about the organism Euglena?

 3. What features are seen in Paramecium but not Euglena?

 Exercise 3:  Features of Plant Cells

             The following procedures will allow you to observe some common organelles of plant cells.  Compare the features of plant cells with that of animal cells.  Identify any similarities or differences.

 Procedure:
            Observe the three plant slides at various levels of magnification.

Materials:
            Microscope
            Allium
            Monocot/Dicot Stems
            Elodea Leaf

 Questions:
1. Identify the cell wall of the Allium plant.

2. What is the significance of the cell wall in plants?

3. What difference do you see when looking at Allium and Elodea?

4. Can you identify a nucleus in the Allium cells?

5. What difference do you see when comparing the monocot and dicot?

6. What are the round, green organelles found in Elodea?

7. What pigment is found in these organelles?

8. What is the function of these organelles?

 

 Exercise 4:  Features of Animal Cells

             We will now look at a few of your cheek cells to demonstrate the typical structure of animal cells.  We will also look at some prepared slides of animal cells on demonstration, including one of gap junctions (interconnecting strands of cytoplasm).  Remember, most of the organelles in animal cells are very small, so you’ll have to look closely to see them.

 Materials:
            Microscope
            Glass slide and cover slip
            Toothpick
            Methylene blue stain
            Demonstration slides of endoplasmic reticulum, mitochondria, and epithelium.

 Procedure:
1. With the BLUNT end of a toothpick, gently scrape the inside of your cheek.
2. Smear the blunt end of the toothpick on a glass slide.
3. Add a very small drop of methylene blue stain to the slide and add a cover slip.

     Caution:  Methylene blue stain can never be removed from clothing.  SO BE VERY CAREFUL!

4. Place your slide in a safe location for about a minute.
5.  Observe slide using high (40x) magnification.
6.  Draw a few cheek epithelial cells and label the nucleus and cell membrane.
 

Questions:
1. How many chromosomes are found inside the nucleus of your cheek epithelial cells?

2. What are some organelles found in onion cells but not in your cheek cells?

3. What organelles do the onion cells and your cheek epithelial cells have in common?

 

Procedure:
1. Observe the turtle liver cell slide on demonstration. 
2. Locate nuclei and nucleoli.
3. Locate some mitochondria in the cells.  You probably won’t be able to make out the shape of the
                mitochondria very clearly, as they are very small.

 Questions:
1. How many nuclei do you see in each cell?  How many nucleoli per nucleus do you see?
2. What is the function of mitochondria?  Why do you think there are so many mitochondria in liver cells?
 

Procedure:
1. Observe the endoplasmic reticulum (ER) slide on demonstration.  See if you can locate some
                  ribosomes on the endoplasmic reticulum—you’ll have to look very closely.

 Questions:
1. Where are ribosomes made in eukaryotic cells? 

2. What do we call ER that has ribosomes attached to it? 

3.  What do we call ER that does not have ribosomes attached to it?

4. What’s the function of the RER?  What’s the function of SER?

 

Procedure:
1. Observe the epithelial cell slide on demonstration showing the intercellular bridges.  In animal cells, the
                    interconnecting strands of cytoplasm between adjacent cells are called gap junctions.

Questions:
1. What might be a function of the gap junctions? 

2. How do plasmodesmata and gap junctions differ?