Laboratory #2 - THE CELL
The purpose of this lab is to introduce you to a few general features of
living cells. When reviewing for a lab exam, you should be familiar with the
following terms, each of which is described in your lab manual:
- cytoplasmic streaming
Organisms are typically classified into 5 different kingdoms: Animalia
(animals), Plantae (plants), Fungi (mushrooms, etc.), Protista
(single-celled eukaryotes), and Monera (bacteria). After completing this lab, you should be familiar with the generalized cellular structure of most of these organisms.
The pictures below are from bacteria observed in lab. The picture on the left is of mixed bacteria while the one on the right is from yogurt. Bacteria represent the most simple
cell structure and these are generally considered to be the most "primitive"
of organisms. Look closely at the picture on the left and you should see the three different shapes of bacteria: (1) cocci (spheres), (2) bacilli (rods), and (3) spirilli
(spirals). Did you know that many types of spirilli actually function like a
cork screw and bore into humans or animals and cause infection? Many types
of cocci and bacilli cause infection as well.
Look closely at the yogurt picture (on the right) and you'll see the milk portion (clumpy, whitish material) and the "living culture" portion (small rod-shaped cells which are actually bacteria).
Questions to consider:
1. Do these organisms have a nucleus?
2. In general, are these cells larger or smaller than eukaryotic cells?
3. Are these cells prokaryotic, eukaryotic, or pseudokaryotic?
This is another example of a prokaryotic cell, Oscillatoria, a blue-green algae.
Actually, blue-green algae are a controversial group of organisms. They are
often considered in the plant kingdom, but most people agree that they are
prokaryotic (they don't posses a nucleus, but they do have an internal
membrane system). Blue-green algae are also commonly referred to as
1. How do these organisms obtain their nutrition?
2. Where do these organisms grow?
3. If the decision was up to you, would you consider these organisms as
prokaryotic or eukaryotic?
The picture below is Elodea, a small aquatic plant that commonly grows in
lakes and is often placed in fish tanks. Did you know that all of these cells
are connected by small pores (plasmodesmata) and the plasma membranes are
continuous between all of the cells?
1. What organelles are responsible for photosynthesis?
2. What structures are found in these cells but are not present in animal
The image below is also from a plant, but notice the cells do not contain any chloroplasts. This slide is from a very thin slice of an onion. Look closely and you should be able to see a nucleus within each cell.
The picture below is from persimmon endosperm. Endosperm is a nutritive tissue found in most seeds- you'll learn more about it in Biology 102. Notice the thick cell walls. Also notice the thin lines that run through the cell walls. These lines are plasmodesmata- very thin channels that connect virtually all cells within a plant.
Many plant cells contain plastids- membrane-bound organelles that either store or manufacture sugars or other metabolic substances. Chloroplasts are one type of plastid. Chromoplasts are another type. The orange color of carrots is due to an abundance of chromoplasts. The picture below shows chromoplasts within carrot cells.
Unlike bacteria and cyanobacteria, which are prokaryotic, the cell that you
see here on the left has a dark blue nucleus in its center and is thus eukaryotic. This
is a human cheek cell which should look very similar to what you saw in lab.
The inside of your mouth is lined with tissue called squamous epithelium and
these cells are easy to remove. Did you know that the nucleus of every one
of your cheek cells (and practically all of your other cells for that
matter) contains all of the genes responsible for your genetic makeup? Even
in cheek cells, there are genes which specify eye color, height, etc., they
just aren't expressed in these cells.
The middle cell and the cell on the right are two protistans that were observed in lab.
1. How are these cells different from plant cells?
2. How are these cells different from prokaryotic cells?
3. What is the outermost layer of these cells - a cell wall or plasma membrane?
This concludes the review for Lab 2 - The Cell.
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