Microscopy Unit C – Cycling of Matter in Living Systems

The Cell Theory Thanks to the accumulated work of many scientists, the Cell Theory Cell Theory was formulated, which states: 1. All organisms are composed of one or more cells 2. The cell is the smallest functional unit of life 3. All cells are produced from other cells ex=174&list=PLEB4B776204CBE2EC

Think, Pair, Share!  Why do you think there were so many heated debates around the development of the cell theory?  Can you describe a time when collaboration worked well for you? Where there ever any disagreements that led to a false assumption (like cells spontaneously crystalizing into existence)?

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There are 2 types of microscopes: 1) Light Microscopes 2) Electron Microscopes

 Compound light microscope: uses two or more lenses on top of each other.  Objects are illuminated by visible light  Just for information:  The practical limit of light microscopes is approximately 1250 – 1500x magnification (because of the size of the wavelength of light). Light Microscopes

Advances for Light Microscopes  What if I’m looking at a transparent specimen?  Staining!  Applying a stain that will dye certain specimen or parts of specimen a different color  Gives us the ability to see it!

Electron Microscopes  Specimen are illuminated with a beam of electrons instead of with light.  Several types:  Transmission electron microscope  Scanning electron microscope  Confocal Laser Scanning microscope  Scanning Tunneling microscope Pollen 

Transmission Electron Microscope  Beam of electrons is transmitted through a thinly-sliced specimen to view internal structures and details  Magnification: x – x 

Scanning Electron Microscope  A beam of electrons is swept over an object, creating a 3D image of external details.  Usual magnification ~ x, but can be as much as x Eyelashes

Confocal Laser Scanning Microscope  For specimen that are too thick for compound light microscopes:  a laser beam is directed at one plane at a time, creating “slices” of images that get “stitched” together.

Scanning Tunneling Microscope  Produces images of molecules like DNA  A metal probe is brought near the specimen, and electrons flow from this to the surface.

Microscope Worksheet  Student Reference 8  page 478  Complete the first page of the handout

 Power of the microscope:  how many times larger the image seen through the microscope is as compared to the actual size of the object (as viewed by the unaided eye). Magnification = (ocular)(objective) Magnification

IF…Ocular = 10x Low Power Objective = 4x THEN… Magnification = (10)(4) = 40x  Magnification is always stated in the lower right hand corner of drawings

Skill Practice  Calculate Magnification  Page 244  A) a 2.5X low-power objective lens and a 10X eyepiece  B) a 100X high-power objective lens and a 10X eyepiece

Magnification vs. Resolution  Magnification:  # of times an image's size is enlarged  For your information:  measured in the degrees of an angle formed by lines running from either end of the image to the vertex at the observer's eye  In practice this simply means that if we view a 1cm line at 2x it appears to us as a 2cm line

Magnification vs. Resolution  Resolution:  measurement of how well the smallest details of an image can be discerned.

Low Resolution

High Resolution

 What you see when you look through a microscope. diameter of the field of view can be found by measuring the distance across the field of view with a ruler. Field of View

 The diameter of the field of view can be found by measuring the distance across the field of view with a ruler. Field of View

 Measurements are converted from mm to µm  1mm = 1000 µm

Procedure to Measure Object Size 1. Determine the diameter of the field of view (FOV) 2. Estimate how many of the object fit across the diameter 3. Divide the diameter by the # that fit across to get the size of the object

Equation  Object size = size FOV # objects across

Medium and High Power FOV  (FOV diameter)(total magnification on low power) = (FOV diameter)(total magnification on medium power) = (FOV diameter)(total magnification on high power) Objective lens FOV Diameter (mm) Total Mag. (10x ocular) 10x (low)2.0 (1.78)100x 40x (med)0.4 (0.45)400x 100x (high)0.2 (0.178)1000x

To calculate the field of view of higher power lenses, follow the following steps: 1. Measure and record the field of view of the low power lens 2. Record the magnification of the low power lens 3. Record magnification of higher power lens 4. Calculate the ratio quotient of the higher power lens to low power lens Field of View

Ratio quotient = magnification of higher power lens magnification of lower power lens 5. Calculate the field diameter of the higher power lens. Field diameter = low power field diameter (higher power) Ratio quotient

Field of View Field diameter = low power field diameter (higher power) Ratio quotient = ____________________mm Convert from mm to  m!!! Do this by multiplying mm by 1000

Final Calculations  Size of Object = size of image (FOV diameter) total magnification  On your drawings, remember to write  Your total magnification  The size of the image  The size of the object

 Compares the size of the drawing to the actual size of the object.  We must know the field of view of the microscope for the particular magnification we are using to view the object.  The field of view is used to estimate the actual size of the object we are observing through the microscope. Scale

Example... Field of view = 4.0 mm We can fit 4 objects across the field of view so the object is 1 mm wide and approximately 3.5 mm long.

Drawing is 28 cm long and 8 cm wide So, 28cm drawing = 3.5mm actual size To determine the scale, reduce drawing size to 1… actual size = 3.5mm = 0.125mm drawing size 28 cm 1 cm SCALE: 1cm = mm Example...

Magnification Worksheet  Complete the second page of the handout

Scientific Techniques to view cells  Staining – applying a dye to cells to make the structures more visible  Centrifuge – spins a sample to separate cells of different sizes and density in order to view cells of only one type

Cell Research (at the molecular level)  Due to new technology, research on cells has led to major breakthroughs in medicine and technology

Gene Mapping  Finding the sequence of chemical subunits of DNA  Technology has allowed mapping of the human genome  Why would we want to do this?  Open our understanding of the way different parts of the genetic material work together  lead to cures and ways to manage disorders & diseases

Cell Communication  Cells are efficient open systems that interact with their environment  Messenger molecules take information from one cell to another and attach to a receptor molecule  Receptor molecule changes shape and creates a chain reaction to carry the message to the proper location  “Lock and Key”  Fluorescent antibody technique: allow diagnoses of diseases carried by viruses, bacteria, protozoans, by showing binding of substances to cell membranes

Cell Communication

X-ray Crystallography  Uses x-rays, special sensors and computer technology to allow scientists to learn the details of molecular structure  Looks at the scattering of the x-rays

Green Fluorescent Protein (GFP)  Injected into gene  Fluoresces under UV light when a certain trait is present  Example: Antibiotic resistance

Stem Cell Research  Adults: found in bone marrow, lipid cells, and portions of blood.  Also found in: umbilical cords and embryos

Lab C2, page  Read Estimating an Objects Size with the Microscope  Read student reference 8 (pg. 478 – 479, & 481)  Once you have read both, grab a microscope  Prepared slides will be a the front of the room, please handle them with care  Complete questions 1-3 and…

Lab C2 Questions:  How did the images of the cells change with increasing magnification?  How is staining useful in observing cells and their structures?  What do the details you observed suggest about the cells’ activities?  Some of the structures you see in the cells may be familiar to you. Make a list of the structures that you recognize, and if you can recall, what functions they have.

Exit Slip  What is one thing that you are still confused about regarding microscopes?  If you could invent one “science gizmo” what would it be? Do you think your invention would lead to any discoveries that would change our understanding of science?