regents biology viewing cells: using the compound light microscope & stains
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Regents Biology
VIEWING CELLS:USING THE COMPOUND LIGHT
MICROSCOPE & STAINS
Regents Biology
I. Parts of the Microscope
1. Eyepiece: Lens closest to the
eye AKA “ocular”
2. Body Tube: Connects the
eyepiece to the objectives
Regents Biology
I. Microscope Parts (continued)
3. Low Power Objectives: Shortest lenses
4. High Power Objective: Longest lens;
closest to the slide DO NOT USE WITH
COARSE FOCUS KNOB
Regents Biology
I. Microscope Parts (continued)
5. Stage: Where the slide
is placed
6. Stage Clips: Clips that hold
the slide in place
Regents Biology
I. Microscope Parts (continued)
7. Diaphragm: Adjusts the amount
of light entering from the light source onto the specimen
8. Light Source: Provides light to
illuminate the specimen
Regents Biology
I. Microscope Parts (continued)
9. Arm: Where you
should always hold & carry the microscope
Base: The bottom of
the microscope
Regents Biology
I. Microscope Parts (continued)
11. Coarse Adjustment Knob: Roughly focuses
the specimen. USE ONLY WITH
THE LOW POWER OBJECTIVE
12. Fine Adjustment Knob Sharply focuses
the specimen on both low and high power
Regents BiologyII. Labeling the Parts
.
.
Regents BiologyII. Labeling the Parts
Body tube
Nosepiece
Low Power Obj.
Med. Power Obj.
High Power Obj.
Stage Clips
Diaphragm
Light
Ocular
Arm
Stage
Course Adj. Knob
Fine Adj. Knob
Base
Regents Biology
TOTAL MAGNIFICATION Powers of the eyepiece (10X) multiplied by
objective lenses determine total magnification.
Regents Biology
IV. Image Appearance When viewing a specimen through a
microscope, the image is distorted.What does that mean?
Images appear upside-down AND backwards
Example: The letter “e”:
Original Image:
Image Under the
Microscope:
Regents Biology
FIELD OF VIEW The area of the slide you view through
the microscope Magnification increase, FOV decreases As you zoom in you see LESS of the
specimen on the slide
Regents Biology
Wet Mount
Wet Mount: liquid suspension observable under a light microscope
1.Place your specimen on a glass slide.
2.Add 1-2 drops of liquid (water) to the slide.
3.Gently lower a coverslip at an angle onto your wet specimen. This reduces air bubbles.
Regents Biology
Wet Mount Slide
Adding solution without removing coverslip:
1. Place pipette with stain near coverslip
2. Place piece of paper towel on opposite side of coverslip
3. Add stain/solution from pipette
Regents Biology
What are stains? How can we test substances for organic compounds?
Chemical Stain: A chemical that is used to make a cell
visible (ex: iodine, BTB) Chemical Indicators: A substance which detects the presence
of a specific element or compound We can test for any organic compound
Regents Biology
Bromthymol Blue
Can be a stain OR indicator
Stains cells blue Indicates presence
of Carbon Dioxide by turning from blue to yellow
Regents Biology
Lugol’s Iodine Test Can be a stain or
indicator Tests for the
presence of Starch A positive test results
in the iodine changing in color from red/brown to BLACK
As a stain, makes cells appear amber
Regents Biology
Benedict’s test
Tests for the presence of glucose
The solution changes from clear blue to opaque ORANGE in a positive test
Regents Biology
Measuring Cell Size
We can use microscopes to estimate the size of cells we are looking at
If we know the diameter of the field of our field of view we can then estimate the size of the cells
1 meter (m) = 1000 millimeters (mm)1 millimeter (mm) = 1000 micrometers (µm)1 meter (m) = 1,000,000 micrometers (µm)
Regents Biology
MICROMETERS μm =
MICROMETER WHAT DOES A
MICROMETER EQUAL?
1,000 μm = 1 mm Conversion:
___mm * 1000 = ____μm
Regents Biology
Measuring Field of View
1. Place metric ruler on the microscope stage we can determine how many millimeters the diameter of the FOV is
Regents Biology
Estimating the size of a cell: Using your estimate of the diameter of the FOV, you can estimate the size of a cell.
Use the formula:
Size of cell = diameter of field # of cells
How many cells fit across the
diameter of the field? ________
If the diameter of the field is 1.5 mm, estimate the size of each cell:
_______ mm
_______ µm
Regents Biology
a) if the field of view = 1 mm
then onion cells are
__________ mm
or ______________(µm) in length
1mm (1000 µm)
Field of view
Onion cell
0.5
500 microns
Regents Biology
b)if the field of view = 0.5 mm or 500µm
then these cheek cells would be
mm or ______________ µm in length
0.5 mm (500 µm)Human
cheek cell
500
5100
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