Cell Identification: Biology Lab

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lab, you'll be studying the physical and chemical characteristics of cells. We'll use these characteristics in a lab where you will be able to identify cells of your own. We'll look at animal cells, plant cells and two types of bacteria cells.

What Are Different Types of Cells?

In class you probably see plastic models of cells that are circular, filled with a sampling of each of the important organelles. But in real life, this is a generalization of a cell. Different cells have different purposes, even within your own body. Your muscle cells are packed with proteins that allow for contraction and movement. You can even see the proteins as striated bands in the microscope. Brain cells have long projections that allows them to send messages over long distances in your body.

Plant cells are packed with chloroplasts, which allow them to make their own food. Even bacteria look different, depending on where they live and how they get their food.

So, how is a scientists supposed to tell all of these cells apart? Looking at physical characteristics under the microscope is one way to accomplish this task. Today, we'll look at how to use a microscope and how to tell the difference between animal cells and plant cells.

Experiment Setup

To do this lab, you'll need a microscope. A microscope that magnifies the object 100 times, or 100x, is needed to see the characteristics of plant and animal cells. However, a microscope that magnifies up to 400x will help you get a bigger picture and much nicer diagrams for your results.

You'll need samples of each of the cells needed. Animal cells can be obtained from scraping your cheek gently with a toothpick and applying the cells to a microscope slide. Animal cells need a small drop of iodine or methylene blue to be seen under the microscope, with a coverslip placed on top.

A thin layer of Elodea, an aquatic plant, works well for an example of a plant cell. Apply a thin slice of Elodea to a microscope slide and place a coverslip over it. Be careful, though, because Elodea is an invasive species in some states. If this is the case in your state, choose a very thin slice of another aquatic plant.

Once you have prepared your slides you'll need to focus your microscope. Start with the lowest objective and bring the slide into focus using the coarse adjustment knob. Then, increase the objective and focus it again using the fine adjustment knob so as not to raise the slide too high. Continue like this until the slide is focused at the highest power needed to see a single cell.

Parts of a microscope

Drawing Cells

Like any good scientist, you'll want to record the results of any experiment, even just from looking under the microscope. Get some paper or your lab notebook and get ready to show off your artistic skills before starting this lab.

Start with a large circle to represent the field of view in the microscope. You're going to be drawing exactly what you see in your field of view. Try to keep the proportions the same to the best of your ability and be sure to label all important structures, which we'll get to next.

Identifying Animal Cells

Sometimes, it's not what a cell has, but what structures it doesn't have that help us identify it. Animal cells are different from plant cells or bacteria because they do not have a cell wall.

A cell wall is a rigid structure outside the cell that protects it. It is what gives a plant cell its characteristic shape. Although all animal cells look slightly different, they will all be rounded, without the sharp edges of plant cells, and large enough to see at 100x under the microscope. The outer edge of the cell is the cell membrane. Make sure to label the line separating your cell from the environment as such.

So, how can we tell animal cells apart from bacteria, which are also round? In the center, you will also see a dark dot that is the nucleus, which stores DNA. Only plant, animal and fungi cells have a nucleus, which makes them different from bacteria. Label the dot in the center nucleus.

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