BIOL1060 Lab 2: Microscopes, Cell Structure and Function

Lab 2: Introduction to Microscopes, Cell Structure and Function

Learning outcome

  • Compare the structural and functional differences between animal and plant cells and their organelles.

Materials (optional): 
microscope to 100x
a prepared onion slide
a prepared bone slide 

Microscope Introduction

We must appreciate how technology informs science. This story starts with the microscope and well-sharpened knives. Before humans designed the first tools to see matter smaller than what can be observed by the human eye, we could not see the inner-workings of biological material. 

Take a moment to really appreciate the amount of work involved in making a magnifying glass. The glass pieces need to be hand-sculpted into a round shape that is convex on one side to focus light into a central place. Then a stand of some sort needs to hold it all in a vertical plane. Through the layers of glass, the focal plane is defined and an internal layer of the object is magnified. The attention of light to a central location facilitates contrast in these layers, which are defined visually by their density and the subsequent absorption of stain applied. 

Read more about Light Microscopy here:

Caprette, D.R. 1995. Light Microscopy. Rice University. https://www.ruf.rice.edu/~bioslabs/methods/microscopy/microscopy.html

Microscope

PBS LearningMedia. 2019. Microscope Activity.  

Visit this website to go through a virtual tutorial about how to prepare and view a slide containing an onion cell and then a bone cell. Take a screen shot of your 100x magnified onion and bone cells. 

NOTE: I have a microscope at my office and I teach labs on campus on Thursdays. You may visit my office hours or lab to use the microscope to do this lab.  If you are not near campus, you might be able to access a microscope on your campus or where ever you are. If you want to do this on your own and not do the virtual lab, you need a a microscope, a prepared onion cell slide and a prepared human bone cell slide. You can come to my office hours to do this part of the lab, or you can use this virtual microscopy activity to complete the lab. Everyone need to submit the same documents. 

–> Onion cell (screenshot copied here):

–> Bone cell (screenshot copied here): 

–> Label this diagram of a microscope:

Labels are: ocular lens, objective lenses, light, fine adjustment, light intensity control, condenser, condenser aperture lever, revolving nosepiece, carrying handle, slide holder, course adjustment, fine adjustment, light intensity control

parts of a microscope student document

A:

B:

C:

D:

E:

F:

G:

H:

I:

J:

 

Cell Size

While learning about the components of a microscope, you viewed an onion slide and a bone slide. 

–> When viewing in the highest magnification, how many cells were on the onion slide in the field of view? (make an estimate based on counting a section of cells in the slide view and then multiplying by the total area or number of rows, etc)

–> When viewing in the highest magnification, how many cells were on the onion slide in the field of view? (make an estimate based on counting a section of cells in the slide view and then multiplying by the total area or number of rows, etc)

–> Describe how you estimated the total number of cells in the viewing area.

 

The field of view with our ocular lens magnification (you figured that out) and the 40x is 0.4mm. 

A penny is 19.05mm. 

Now you have several pieces of information to answer the next question.

–> How many onion cells fit across the surface of a penny? Show your math work.

 

 

 

penny

Next two questions: You need to do the virtual lab to figure this out. If you are using a microscope in my lab or on your own, please note that. 

–> What is the total magnification when you are viewing under the lowest power?

–> What is the total magnification when you are viewing under the highest power?

 

Cell Structure and Function

Next two questions: You need to do the virtual lab to figure this out. If you are using a microscope in my lab or on your own, please note that. 

–> When viewing the onion cell, what is the purple-blue part of each cell?

–> When viewing the onion cell, what is the lighter blue part of each cell?

–> Write three key differences you observed between the onion and bone cells. 

1. 

2.

3. 

 

Let’s appreciate one driving principle of biology: Cell Theory. All organisms are made up of cells. And what is contained in those cells is shockingly similar. This lends evidence for Common Ancestor Theory. All living organisms evolved from a common ancestor. 

Animal cells differ from plant cells in very few ways. Plant cells have extra organelles because they do the work of primary production. They assimilate the sun’s energy into glucose molecules that drive cellular respiration in all living organisms. 

Both plant and animal kingdoms contain eukaryotic organisms. There are more differences between prokaryotes and eukaryotes than there are differences between animals and plants. Prokaryotes have no membrane-bound organelles. We will discuss them in greater detail in a future lab. For now, let’s consider organisms with membrane-bound organelles. These include protists, animals, plants, and fungi. We will define the structure and purpose of each organelle found in cells. 

plant cell

 

animal cell

 

In discussion, we are surely developing a list of organelle definitions so you don’t have to do this here. Visit the discussion or the textbook to understand more about the different organelles. 

Organelle Spotlight: Golgi Apparatus

Answer the following questions to demonstrate your understanding. 

Recommended Supplemental Reading:

Davidson, M.W. 2019. The Golgi Apparatus. Florida State University. https://micro.magnet.fsu.edu/cells/golgi/golgiapparatus.html

Here is an high magnification transmission electron microscope image of a human leukocyte, showing Golgi vesicles. 

human leukocyte showing Golgi

–> What is the function of the Golgi Apparatus? Are they membranous organelles?

 

–> How is the Golgi apparatus functionally different in plants and animals? Why?

 

Organelle Spotlight: Mitochondria

The mitochondrion (plural mitochondria) is a double-membrane-bound organelle found in most eukaryotic organisms.

mitochondria

 

–> What is the function of mitochondria?  

 

 

lab 2 molecule

–> What molecule is this? Just take a guess. Look at the elements in it and think it through. I am sure you know. 

 

–>What does this molecule have to do with mitochondria?

 

–> Reach for it- When this molecule is consumed in cellular respiration (next lab topic!), what part of this molecule breaks off- the blue hexagonal-pentagonal complex, the pink pentagon, or the green circles?

 

 

 

 

→ Write 100+ words of reflection about your learning experience in this lab (free-write):

 

Do yourself a favor- Now read the next lab …. and if you are really ambitious, you will go right ahead a read (and participate!) in the next discussion. Knowing what you have to do and how you will be assessed is your first step to success. 🙂