Regents Biology

VIEWING CELLS:USING THE COMPOUND LIGHT

MICROSCOPE & STAINS

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I. Parts of the Microscope

1. Eyepiece: Lens closest to the

eye AKA “ocular”

2. Body Tube: Connects the

eyepiece to the objectives

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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

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I. Microscope Parts (continued)

5. Stage: Where the slide

is placed

6. Stage Clips: Clips that hold

the slide in place

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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

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I. Microscope Parts (continued)

9. Arm: Where you

should always hold & carry the microscope

Base: The bottom of

the microscope

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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

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TOTAL MAGNIFICATION Powers of the eyepiece (10X) multiplied by

objective lenses determine total magnification.

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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:

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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

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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.

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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

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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

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Bromthymol Blue

Can be a stain OR indicator

Stains cells blue Indicates presence

of Carbon Dioxide by turning from blue to yellow

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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

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Benedict’s test

Tests for the presence of glucose

The solution changes from clear blue to opaque ORANGE in a positive test

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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)

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MICROMETERS μm =

MICROMETER WHAT DOES A

MICROMETER EQUAL?

1,000 μm = 1 mm Conversion:

___mm * 1000 = ____μm

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Measuring Field of View

1. Place metric ruler on the microscope stage we can determine how many millimeters the diameter of the FOV is

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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

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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

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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