Microscopes The Discovery of Cells

Quiz Number paper from 1-5 Identify the following pictures

Question 1

Question 1: Bacteria

Question 2

Question 2: DNA

Question 3

Question 3: Breast Cancer Cell

Question 4

Question 4: Alga- red tides

Question 5

Question 5: Bed bug

Learning Targets 1. Describe how a microscope works. 2. Calculate the total magnification of an image. 3. Compare the different types of microscopes. Why? To see microscopic world

How does a microscope work? Magnification enlargement of an object compare size of image to actual size of object total magnification ocular power x objective power = total magnification

Microscopes

Resolution – capacity to show 2 points that are close together as separate.. 10x1000x Poor Resolution = Blurry Image Good Resolution = Clear Image

Resolution

How does a microscope work? Parfocal both low and high power objectives are adjusted to the same focus easily switch between both objectives

What happens as magnification increases? 1. field of view decreases 2. brightness decreases 3. resolving power increases

Staining  Coloring cell structure With dyes to reflect light  Certain cell parts absorb certain stains  Kills cells or disturbs contents  Vital stains-dyes that highlight structures in living cells

What are the different types of microscopes? Compound light microscope Stereoscopic dissecting microscope Electron microscope

Compound Light Microscope

has 2 or more lenses (eyepiece and objective) uses transmitted light (light passes through object) must use thin specimen so light can pass thru can use live specimens usually doesn’t exceed total mag. of 2000x Our scopes in class are capable of 400x only see specimen in 2D

Compound Microscope Images Human Hair (x 400) Mite Paramecium

Compound Light Microscope Structures & Functions

Compound Light Microscope Eyepiece/Ocular – The lens through which the scientist looks Body Tube – Connects eyepiece to microscope Revolving Nosepiece – Holds 3-4 objectives (magnifying lens), turns for objective selection.

Compound Light Microscope Scanning Objective - Used for locating objects & scanning the slide quickly (Red Line- 4X) Lowest power objective Low Power Objective – Lens that allows you to find & center the object on a slide. Yellow line around the objective (10x) High Power Objective - Lens that zooms in for closer viewing (40X) Blue line around high power

Compound Light Microscope Stage – platform upon which the slide rests Mechanical Stage – movable clips that hold & move the slide Iris Diaphragm – transparent lens through which light travels. Size and brightness can be adjusted. Lamp – light source needed for viewing the specimen

Stereoscopic Dissecting Microscope uses reflected light to produce image range of magnification 10x-60x

Images from a Stereoscope Penny – Abe’s face Penny – back Beetle

Stereo Dissecting Microscope 2 eyepieces to produce 3-D image Uses reflected light to illuminate surface of specimen Used on large objects which light cannot pass through Magnifies object 5x – 60x

Electron Microscope 2 Types Scanning electron microscope (SEM) Transmission electron microscope (TEM)

Electron Microscope Discovered in Germany in 1930’s and 1940’s Uses beam of electrons to see image NOT light Image is produced on a T.V. monitor in black & white (no light) Much higher resolution Limitations Can’t view living things due to vacuum in interior Very expensive Very big, must have own foundation

Transmission electron microscope (TEM) Electrons go through very thin slice of specimen – detailed image on T.V. screen 200,000x (can be increased to 1,000,000x)

Images from a TEM Bacteria E.coli bacteria dividing Leaf

Scanning electron microscope (SEM) Beam of electrons across a whole specimen (sprayed with fine metal coating) 3 dimensional view of surface features on T.V. screen 100,000x

Scanning Electron Microscope uses reflected electrons to produce image

Images from a SEM Dentist Drill (x 50) Hypodermic Needle (x 100) Mosquito (x 100) Toilet Paper (x 500)

Phase Contrast: living cells Blood Cheek cell

WHICH SCOPE WOULD BE BEST TO USE TO LOOK AT: A pollen grain Mold on a piece of bread Bacteria Nucleus of a cell Grasshopper