1. Catalyst
Grab a sheet from the front and begin reading through it and follow the steps for using the microscope.
Microscopes are in the cabinets in the other side of the room.
You should also be highlighting any important terms you see or anything that isn’t clear to you so that we may discuss it as a class.
Once you have read through and practiced with the microscope I would like for you to answer the practice questions at the end.

2. Cell Microscopy

3. Introduction
Robert Hooke examined slices of cork under a microscope and decided to call the ‘pore-like’ structures cells.
Robert Hooke, through his observations, had discovered and described in his book the fundamental unit of all living things.
About 200 years later, a general cell theory was proposed using the works of German scientists Schleiden (botanist, 1838) and Schwannn (zoologist, 1939).
The cell theory states:
The basic unit of structure and function of all living organisms is the cell.
All cells arise from pre-existing cells by cell division. (Virchow, 1855)
Cells a very similar to a bag in which the chemistry of life is allowed to happen. This is permitted because the cell is partially separated from its external environment by a thin, partially permeable membrane.
The cell’s membrane is a very effective barrier, but also allows for certain materials to move in and out of the cell. This partial permeability allows for the cell to maintain a stable environment for optimal function. (homeostasis)

4. Cell Microscopy
The branch of biology that studies cells is known as cell biology (normal cellular anatomy). Although cells can be studied using various methods, scientists began by “looking” at the cells using different types of microscopes.
Nowadays, we use 2 fundamentally different types of microscopes. Both of the microscopes use a form of radiation in order to create am image of the specimen that is being examined.
The light microscope uses light as its source of radiation.
The electron microscope uses electrons.
Early in the nineteenth century, dramatic improvements were made in the quality of glass lenses which allowed for rapid progress in microscope design and in preparing material for examination with microscopes.
Cytology is the branch of biology that deals with the study of cells in terms of structure, function, and chemistry.

5. Light Microscopy
Compound Light Microscope

6. Animal vs. Plant Cells DIFFERENCES
There are many similarities and differences between animal and plant cells. In order to see and identify certain cell structures under a microscope the specimens need to stained.
DIFFERENCES
A centriole, a small structure near the nucleus involved in cell division, is only found in animal cells.
Plant cells are usually much larger than animals cells, so they are easier to see under a light microscope.
Plant cells are also surrounded by a cell wall, a rigid membrane that surrounds the plasma (cell) membrane.
The cell wall gives the cell a definite shape and prevents it from bursting when water enters the cell, increasing the internal pressure.
Neighboring plant cells are linked by fine strands of cytoplasm called plasmodesmata.
Plant cells possess a large central vacuole surrounded by the tonoplasts.
The central vacuole is composed of a solution of mineral salts, sugars, O2, CO2, pigments, enzymes, and other organic compounds including waste products.
The tonoplast controls any exchange between the cytoplasm and the vacuole.
Chloroplasts are large green organelles found mainly in the leaves of plants used in photosynthesis.

7. Animal vs. Plant Cells SIMILARITIES
A thin, partially permeable plasma (cell) membrane that surrounds the cell.
A relatively large nucleus containing chromatin, a mass of loosely coiled threads.
Chromatin condenses to form the visible separated chromosomes used during cell division.
DNA, a molecule which contains the instructions that control the activities of the cell.
Loops of DNA form the nucleolus within the nucleus.
The cytoplasm, a jelly-like fluid that is in between that plasma membrane and the nucleus.
Organelles, small and distinct functional and structural parts of the cell.
Each organelle is separated from the cytoplasm by its own membrane. (compartmentalisation)
This allows the cell to show division of labor, in which the work to reach the cell’s ultimate function is shared among the different specialized organelles.
Mitochondria is the most abundant organelle seen with a microscope responsible for aerobic respiration.
The Golgi apparatus, a part of a complex internal sorting and distribution system found within the cell.

8. Animal Cell

9. Plant Cell

10. Measurement in Cell Studies
When measuring objects in the microscopic world, small units of measurement should be used. The basic unit of length using the International System of Units (SI units) is the meter (m).
However, in order to measure some of these microscopic objects we must sometimes use units even smaller than the millimeter (mm).
Units of measurement relevant to cell studies
Fraction of a meter
Unit
Symbol
One thousandth = = 1/1000 = 10-3
millimeter mm
One millionth = = 1/ = 10-6
micrometer μm
One thousand millionth = =
1/ = 10-9
nanometer nm

11. Measuring Cells Stage micrometer scale = Eyepiece graticule division
An eye-piece graticule can be used when measuring cells and organelles under a microscope. The eye-piece graticule is a transparent scale which is placed in the microscope eyepiece. This allows the object to be measured while it is being observed.
However, before you can determine the correct size of a specimen, the eyepiece graticule must be calibrated. This is done by placing a miniature transparent ruler (stage micrometer scale) on the stage of the microscope and focusing it .
Once the scales are superimposed, you can find the value of each eyepiece graticule division by:
Stage micrometer scale = Eyepiece graticule division
Eyepiece graticule scale
Once the measurement for each division is found, then observe how many divisions the specimen measures and you can find the actual diameter of your specimen.
Number of X Value (measurement) = Actual diameter of
divisions of each division specimen

12. Magnification and Resolution
Magnification is the number of times larger an image is compared with the real size of the object.
Magnification = size of image
actual size of specimen
NOTE: Make sure that when calculating magnification ALL units are the SAME!!!
Resolution is the ability to distinguish between two separate points. If 2 objects are closer together than the resolution of the apparatus used, then the objects cannot be distinguished as separate.
An increase in magnification is not necessarily accompanied by an increase in resolution.

13. The Electromagnetic Spectrum
Light is capable of traveling in waves. However, the length of the waves of light varies and can be distinguished by the human eye and changed into specific colors by the brain.
The range of the variation of wavelengths is the electromagnetic spectrum.
The longer the waves, the lower the frequency.
Energy changes wavelengths. The greater the energy, the the shorter the wavelength.
The limit of resolution is
about one half the
wavelength of the radiation
used to view the specimen.
If the object is smaller than
half the wavelength of the
radiation used to see it, then
the object will not be
separated from nearby
objects.

14. The Electron Microscope
In order to observe objects smaller than 200nm, scientists needed to use radiation with a shorter wavelength than visible light. The best solution was the use of electrons.
When electrons gain too much energy, they escape from their orbits and behave much like electromagnetic radiation. Therefore, since they are high energy, they have shorter wavelengths.
Electrons are a great form of radiation for microscopy because
Their wavelength is extremely short.
They are negatively charged, so they can be focused using electromagnets.
There are two types of electron microscopes used today.
The transmission electron microscope (TEM) has the electron beam passing through the specimen before it is viewed. Unfortunately, the only portion of the specimen that can be seen is the parts where the electrons have actually passed through.
The scanning electron microscope (SEM) uses the electron beam to scan the surfaces of the specimen and only the reflected beam is observed. This allows for surface structures to be seen as well a greater depth of field to be obtained, which allows the specimen to be in better focus. However, the SEM cannot achieve the same resolution as the TEM.

15. The Electron Microscope - Continued
Although the electron microscopes are better for observing specimens, there are a few disadvantages.
Electrons cannot be seen with the naked eye, so the electron beam has to be projected onto a fluorescent screen. The areas of the screen that are hit by the electrons shine brightly, giving a black and white image.
In order to improve the contrast, stains that contain heavy metal atoms are used. These heavy metal atoms stop the passage of electrons resulting in a better image.
In order to achieve a sharper image, the electron beam, the specimen, and the fluorescent screen need to be placed within a vacuum. This prevents the electrons from colliding with air molecules.
In addition, all specimens need to be dehydrated before being placed in a vacuum to prevent water from the specimen to boil, evaporate, and collide with the electrons. Therefore, only dead material can be examined under an electron microscope.

16. TEM vs. SEM SEM micrograph of bacteria TEM micrograph of a cluster
of silicified Calothrix filaments.
SEM micrograph
of blood cells.
SEM micrograph of bacteria

17. Cheek Cell Staining lab

18. Exit assignment!!
Grab a text book and begin writing the following definitions in your notes. (Use chapter 1 and the glossary.)
cell biology
centrioles
cilia
cytology
chromatin
flagella
cell
DNA
chloroplasts
cell theory
chromosomes
microscope
Prokaryote
endoplasmic reticulum (ER)
eyepiece graticule
eukaryote
smooth ER
stage micrometer
tissue
rough ER
magnification
organ
golgi apparatus
resolution
system
lysosomes
electromagnetic spectrum
nucleus
mitochondria
nucleolus
plasma membrane