Description
*Lab is not needed to complete this assignment* You are simply making notes based on facts as in what will happen in the situations. Answer all questions and make notes for all statements.
Background
Figure 1. Frozen Grass and Flowers
Can Frozen Organisms Come Back from the Dead?
In the 1997 Warner Bros. movie
Batman and Robin,
Mr. Freeze froze his sick wife so that he could defrost her once he figured out a cure for her illness. Former Red Sox baseball player, Ted Williams, was cryogenically frozen after his death in hopes of his health being restored by future technology. While the idea of cryonics sounds crazy, does that mean it would not work?
undefined
Cells are often specialized, or modified to carry out particular functions. The cell’s structure impacts its own function and the function of the tissues that it makes up. If the structure is altered, such as by freezing the water in the cell (Figure 1), the functions of the cell and tissue may be negatively impacted. Therefore, cryogenic freezing presents a major obstacle in that freezing cells can cause the water within the cell to form crystals, which can lead to tissue damage.
undefined
However, research from Japan might give you hope. It shows that vibrating water with magnetic fields prevents freezing. When the magnetic field is turned off, the water in the cells instantly freezes evenly, preventing tissue damage. Therefore, the change in the cell’s structure would not negatively impact its function.
Relationship between Form and Function
A common theme in biology is that function follows form.
Macroscopic
means to be seen with the naked eye. For example, at the macroscopic level, the elongate neck of a giraffe can be observed (Figure 2). A long neck enables the animal to eat plants that are up high that other herbivores cannot reach. The flat, spread out form of a plant leaf that a giraffe eats increases its surface area to maximize the capture of sunlight energy for photosynthesis.
Figure 2. Giraffe Eating Plants That Are Up High
The same principle applies at the
microscopic
level, which means to be visible only with the aid of a magnifying lens. Here, the nerve cells signaling the mouth muscles of the giraffe to chew are elongated, which allows the nerve impulse to travel greater distances in less time (Figure 3). Nerve cells must relay the signal from the brain to the mouth, so speed is important.
Figure 3. Motor Neuron Nerve Cell Structure: This diagram shows the elongated axon of a motor neuron, which transfers the nerve impulse from the cell body to the muscle fibers, signaling them to work.
undefined
The cells of the plant leaf can also be seen at the microscopic level. The epidermal cells are flattened into a thin layer covering the surface of the leaf, which provides protection for the internal structures.
Multicellularity and Cell Specialization
Both giraffes and the plants they eat are examples of
multicellular
organisms. This means they consist of more than one cell, usually with numerous different cell types dividing the labor of the organism. This is called
cell
specialization
. Specialized cells have shapes specific to their function. They also contain certain types of organelles as well as relative numbers of those organelles needed to carry out their function.
For example, red blood cells are donut-shaped, which increases the cell’s surface area, allowing it to carry more oxygen. Adipose cells are large and bulky and, therefore, suited for fat storage and insulation. Sperm cells have a long tail called a flagellum that allows them to travel great distances for egg fertilization. Muscle cells are able to get the body moving because they contain well-above-average amounts of mitochondria, which are the cell’s powerhouses. All the different cell types that make up an organism work together to keep the organism alive.
Studying Cells
Cells are the building blocks of life. The size of a human skin cell is about 30 micrometers (30 × 10-6 meters), which is too small to see with the naked eye. It took the invention of the microscope to be able to study cells. A typical light microscope allows you to see small objects, such as cells.
Cell Structure
All cells have:
A
plasma membrane
that acts as a barrier between the cell’s inner components and its surroundings
Cytoplasm
, which is the semifluid matrix that fills the cell and contains all the dissolved and suspended ions and other molecules needed to keep the cell alive
A central location for hereditary material
Ribosomes for protein synthesis
All of these structures, except the protein-synthesizing ribosomes, can be viewed with a light microscope.
Prokaryotes
Prokaryotes are the oldest and most structurally simple organisms on Earth. The size of prokaryotes ranges from 2 – 8 µm long. Due to this small size, cell shape is the only characteristic of prokaryotes that can be seen with a light microscope. Prokaryotic cells can generally be divided into categories based on three cell shapes:
Rod-like
Round
Spiral
Eukaryotes
Eukaryotes are much more complex organisms. Eukaryotic cells are divided into organized, membranous compartments. This is important because metabolic processes that need different conditions can occur simultaneously within the cell without interfering with each other.
undefined
Plants, animals, protists, and fungi are all types of eukaryotes. Eukaryotic cell size typically ranges from 20 – 80 µm long. This larger size allows for some of the eukaryotic cell structures to be seen with a light microscope.
Plants
Most plant cells have the following structures that can be seen with a light microscope (Figure 4):
A
cell wall
for sturdier stature, usually made of cellulose and pectin
A
central vacuole
for storage and water balance
Chloroplasts
for photosynthesis
Cytoplasm
A nucleus
, which is a membrane-bound structure where a majority of the cell’s hereditary information is found
Figure 4. Basic Plant Cell Structure
Animals
With a light microscope, the following structures of animal cells can be seen (Figure 5):
Nucleus
Cell membrane
Cytoplasm
If present, a
flagellum
, which is a long, thin, tail-like structure used for locomotion
Figure 5. Basic Animal Cell Structure
Protists
Protists are typically larger cells and are very diverse in their structural components. When present in a protist cell, the following structures can be seen with a light microscope (Figure 6):
Nucleus
Cytoplasm
Contractile vacuole
that serves an excretory role
Food vacuole
that aids in digestion
Cell membrane
Pseudopodia (pseudopods)
, which are fingerlike projections that aid in locomotion and the capture of food particles
Cilia, which are short, hairlike projections that usually line the outer cell membrane to aid in locomotion
Oral groove
, where food particles are ingested
Gullet, which is the oral cavity just past the oral groove where food vacuoles form
Chloroplasts
Flagellum
Figure 6. Basic Protist Cell Structure
Microscopy
Studying diagrams of cells is helpful. However, they are only general schematics. No two cells are alike, so the best way to understand the structure of different cells is to observe them directly. Microscopy allows you to do just that.
undefined
Light microscopes work by bending visible light through glass lenses to magnify an object.
Magnification,
or the increase in apparent size, is only one aspect of light microscopy and is thought to be almost infinite in magnitude. A common type of light microscope has multiple objectives, making it a
compound light microscope
.
undefined
Compound light microscopes typically have three or four objectives, which are the lenses that increase the size of the image of an object, with magnifications such as 4X, 10X, 40X, and 100X. The eyepiece has its own magnification, which is typically 10X. Many microscopes, including the Radiance Virtual Microscope (RVM), now employ a camera lens that acts as the ocular lens, which sends the image to a computer for viewing. The magnification of the lens on top of the RVM is 10X. The total magnification of the view can be calculated by multiplying the magnification of the eyepiece by the magnification of the objective being used, as shown in the equation below.
undefined
total
magnification
=
eyepiece
magnification
×
objective
magnification
About This Lab
In this lab, you will study the world of the individual cell. The cell is considered the building block of all organisms. You will note that different types of cells differ enormously in structure and function.
undefined
In this lab, you will learn about the Radiance Virtual Microscope (RVM) that you can use to see cells and other tiny objects. The RVM operates like a real microscope from the convenience of your computer. As you go through the lab’s procedures, you will be introduced to the RVM and you will look at some cells with it.
Open the simulation by clicking on the virtual lab icon below. The simulation will launch in a new window.
You may need to move or resize the window in order to view both the Procedure and the simulation at the same time.
Follow the instructions in the Procedure to complete each part of the simulation. When instructed to record your observations, record data, or complete calculations, record them for your own records in order to use them later to complete the post-lab assignment.
Procedures
This lab requires you to use the virtual microscope. Click
here for a short video
about how to use the features and functions of the virtual microscope.
Experiment 1: Onion Root Cells
Take the microscope from the Instruments shelf and place it onto the left side of the workbench. Be sure it does not hide the shelves.
Take the onion root slide from the Containers shelf and place it onto the microscope stage. When the slide loads, you will see the magnified onion root. You are viewing the slide with the 4X objective lens of the microscope, which is positioned over the center of the slide.
Working comfortably with the virtual or classroom microscope requires getting up close to it. In the virtual lab, use the lab navigation controls at the bottom right of the lab to zoom in. Use the pan buttons to move around the screen.
Click and drag the coarse focus knob located near the base of the microscope on the left side to make the image clearer.
Click the objective to the right of the one pointing straight down to advance from 4X to 10X objective magnification. If the image looks out-of-focus as you increase the magnification, use the fine focus knob located near the base of the microscope on the right side to get a clearer image.
Repeat step 5 until either you can no longer increase the objective magnification or you cannot see the entirety of a cell in your field of view. If you advance further than that which allows a whole cell to be seen, click on the objective to the left of the current one to go back a step, so that a whole cell can be seen.
If there are multiple cells in your field of view, choose one. Observe the cell and then record to reference later:
The total magnification of the image
A general description of the shape of the cell
The color of the cell
Using the annotation and draw overlay tools, label the following:
Cell wall
Cytoplasm
Nucleus
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
When you are done, change the microscope back to the lowest objective.
Drag the slide back to the Containers shelf.
Experiment 2:
Amoeba
Take the
Amoeba
slide from the Containers shelf and place it onto the microscope stage.
Click and drag the coarse focus knob located near the base of the microscope on the left side to make the image clearer.
Click the objective lens to the right of the one pointing straight down to advance from 4X to 10X objective magnification.
Repeat step 3 until either you can no longer increase the objective magnification or you cannot see the entirety of a cell in your field of view. If you advance further than that which allows a whole cell to be seen, click on the objective to the left of the current one to go back a step, so that a whole cell can be seen.
If you need to move the slide to be able to see a whole cell in your field of view, use the
x
-axis and
y
-axis stage adjust knobs. Click and drag the
x
-axis stage adjust knob to move the slide and image from side to side. Click and drag the
y
-axis stage knob to move the slide toward you and away from and the image up and down.
If there are multiple cells in your field of view, choose one. Observe the cell and then record:
The total magnification of the image
A general description of the shape of the cell
The color of the cell
Using the annotation and draw overlay tools, label the following:
Nucleus
Cell membrane
Cytoplasm
Food vacuole
Pseudopodium
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
When you are done, change the microscope back to the lowest objective. Then, drag the slide back to the Containers shelf.
Experiment 3:
Spirogyra
Take the
Spirogyra
slide from the Containers shelf and place it onto the microscope stage.
Repeat steps 2 – 6 from Experiment 2.
Using the annotation and draw overlay tools, label the following:
Cell membrane
Cytoplasm
Nucleus
Chloroplast
Cell wall
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
When you are done, change the microscope back to the lowest objective. Then, drag the slide back to the Containers shelf.
Experiment 4:
Paramecium
Take the
Paramecium
slide from the Containers shelf and place it onto the microscope stage.
Repeat steps 2 – 6 from Experiment 2.
Using the annotation and draw overlay tools, label the following:
Cell membrane
Cytoplasm
Nucleus
Food vacuole
Contractile vacuole
Cilia
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
When you are done, change the microscope back to the lowest objective. Then, drag the slide back to the Containers shelf.
Experiment 5:
Euglena
Take the
Euglena
slide from the Containers shelf and place it onto the microscope stage.
Repeat steps 2 – 6 from Experiment 2.
Using the annotation and draw overlay tools, label the following:
Cell membrane
Cytoplasm
Nucleus
Flagellum
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
When you are done, change the microscope back to the lowest objective. Then, drag the slide back to the Containers shelf.
Experiment 6: Cheek Cells
Take the cheek cells slide from the Containers shelf and place it onto the microscope stage.
Repeat steps 2 – 6 from Experiment 2.
Using the annotation and draw overlay tools, label the following:
Cell membrane
Cytoplasm
Nucleus
Increase the magnification, if necessary, to see these structures. Take a screenshot of the image in order to upload and submit it later.
Clear the bench of all slides and instruments by dragging them back to the shelves, then return to your course page to complete any assignment for this lab.
