Lab 2: Cells
Which one of the following substances
is not a lipid?
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A) wax
B) cholesterol
C) cellulose
D) steroids
E) triglycerides
You now know that the old cliche "oil
and water don't mix" is true. Why?
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A) Oil exhibits polarity and water does not.
B) Water exhibits polarity and oil does not.
C) Oil is hydrophilic.
D) Water is hydrophobic.
E) Oil is an organic compound and water is
not.
A molecule with the formula
C55H110O55 is probably a(n)
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A) oil.
B) steroid.
C) wax.
D) protein.
E) polysaccharide.
All living things are made of cells
• Cells are the basic unit
of living things
• All cells come from
other cells
• This is the classical cell
theory
Cells are small
• Most bacteria are .52µm in size
• Light microscope’s
limit= ~500nm=.5µm
• Single eukaryotic cells
are larger, but still to
small to see without
magnification
Microscopes allow us to see the world of
cells
• Microscopes use
multiple lenses to
magnify small things
Measuring the world of the small
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We use the metric system
The metric system uses powers of 10
Major metric prefixes are 1000-fold apart
English-Metric conversions:
1 meter = 1.09 yards
1 centimeter = .4 inches
Metric interconversions
1 m = 100 cm
1 cm = _____m
The Metric System
• Decimal system (powers of 10)
• Base units (meter, gram) modified by prefixes:
kilo = thousand
centi (c) = hundredth
milli (m) = thousandth
micro (µ) = millionth
nano (n) = billionth
1000.0
0.01
0.001
0.000001
0.000000001
The Metric System
• How do you convert from one metric unit to
another?
• Each decimal place represents one power of
10.
• 1.0 meter =
100 or 102 centimeters (cm)
1000 or 103 millimeters (mm)
1,000,000 or 106 micrometers (µm or microns)
1,000,000,000 or 109 nanometers (nm)
The Metric System
• Example: 1.0 cm = ? m
– Since a centimeter is a hundredth of a meter, it is
10x10 or 2 decimal places smaller than a meter.
– So, move the decimal point 2 places to the left:
1.0 cm = 0.01 m
The Metric System
• Example: 1.0 cm = ? mm
– First put both in terms of meters:
1.0 m = 100.0 cm = 1000.0 mm
– How many powers of ten (decimal places) are
there between cm and mm?
– If 100.0 cm = 1000.0 mm, then
1.0 cm = 10.0 mm
– So to convert from cm to mm, you must multiply
by 10 (move the decimal point one place to the
right).
To convert…
A. Meters to centimeters,
B. Micrometers to meters,
C. Millimeters to micrometers,
D. Micrometers to centimeters,
…we must…
a. multiply by 100.
b. divide by ________.
c. _________ by ________.
d. __________ by ________.
To convert…
A. Meters to centimeters,
B. Micrometers to meters,
C. Millimeters to micrometers,
D. Micrometers to centimeters,
…we must…
a. multiply by 100.
b. divide by _1000___.
c. _multiply__ by _1000___.
d. ____divide by __10,000 .
Using a Light Microscope
1. Get microscope from cabinet
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Carry with one hand holding arm and the other
supporting the base
Arm
Base
Using a Light Microscope
6. Nosepiece
7. Objectives
8. Stage
1. Ocular
(eyepiece)
2. Arm
3. Coarse focus knob
9. Stage clips
10. Diaphragm
11. Light source
4. Fine focus knob
5. Base
Calculating Magnification
• Ocular lens (10X) x Objective lens
Field of View
• Actual diameter of
microscope image
at a certain mag.
• As magnification
increases, field of
view _______.
Using a Light Microscope
• Letter “e”
– Practice steps for observing specimens
– Draw what you see at different powers
– Calculate total magnification
• Silk threads
– Get a sense of ‘depth of field’ (how deep can
lenses focus at different powers)
– Try to determine relative positions of threads (top,
middle, bottom)
Cells can be placed into two categories
• Prokaryotic and
eukaryotic
• Prokaryoticsmaller and
simpler
• Eukaryotic- larger
and more complex
• Eukaryoticcontaining
membrane-bound
organelles
Observing Cells
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Onion Cells
Cheek cells
Elodea cells
Elodea cells (in salt water)
Pond water
Cell structures- Animal cell
Cell structures- Plant cell
Your instructions for the lab
• 1. Draw each subject in detail. Label 2
organelles.
• 2. Using field of view, estimate size of specimens.
• 3. On back of paper, compare and contrast:
– Onion vs. elodea
– Elodea in salt vs. elodea in fresh water
– Plant vs. animal cells
• 4. Describe drawn pond water organism. What
does it look like? Size? What do you think it is?
Categorize it. Unicellular? Plant or animal? Etc.
Using a Light Microscope
• Cleaning up:
– Remove and return your slides.
– Put the scanning objective in place and lower it all
the way down.
– Roll up the lamp cord neatly.
– Carefully return your microscope to the shelf
where you got it.
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