Metric, Microscope and Cell Structure
Metric System is the standard system of measurement in the
sciences. It is convenient because all conversions between units are
increments of 10.
Some important prefixes:
Mega (M) 109
Kilo (k) 103
Deca (da) 101
Deci (d) 10-1
Centi (c) 10-2
Milli (m) 10-3
Micro (µ) 10-6
Nano (n) 10-9
Converting between different magnitudes (prefixes) requires moving
the decimal point forward or backward corresponding to the difference
between the two numbers. The first step you must take is to ask yourself if
you are converting from a larger to a smaller quantity or from a smaller to a
larger quantity. This will tell you if your answer will be large or small.
Example: If we want to convert from 5000 m to km, you know that km are
larger than m, so your answer will be small (5). If we want to convert 50 Mm
to mm, you know that Mm are far larger than mm, so it will require many mm
to equal 50 Mm (5 x 1013).
Next, determine how far you need to move the decimal place.
Example: When converting from nm to m, you must move the decimal place 9
times to the right (as we are going from a small to a large quantity, our
answer will be small – it takes a lot of a small unit to equal one large)
For a further explanation of the metric system, refer to page 17 of
your lab manual.
Questions
- 1 µm (micrometer) = _____0.000001 __m (meters).
- How many µm are in 1 mm? ________1000________.
- How many nm are in 1 mm? ______100000______.
- 12 mm equals how many cm? _________1.2_______.
- 980 mm equals how many m? _________0.98_____.
-
10 mg (milligram) = ______0.001_________g (grams).
How many µg are in 10 mg? ____10000__________.
How many ng are in 10 mg? __10000000_________.
140 mg equals how many g? ______0.140__________.
1500 g equals how many kg? _________1.5_______.
Microscopy
The list of microscope parts and directions for focusing the
microscope are on page 14 of your lab manual.
Inversion – the image in a microscope is upside down and reversed.
To find the true magnification of a microscope, multiply magnification
of the objective and ocular lenses.
Objective
Ocular Lens
Objective Lens
Scanning power
Lower power
High power
Oil immersion
4x
10x
40x
100x
10x
10x
10x
10x
Total
Magnification
40x
100x
400x
1000x
Microscopic Observations
Animal vs. Plant cells.
1) Animal cells have a plasma membrane while plant cells have a cell wall.
2) Plant cells have chloroplasts to obtain energy from the sun while animal
cells do not.
3) Plant cells are rigidly stacked together while animal cells do not have a
high level of organization.
Animal Cell Structure
A list of organelles in an animal cell is found on page 38 of your lab
book.
Tonicity
Isotonic – Same amount of solutes inside and outside of the plasma
membrane. The potato remains the same as before it was placed in solution.
Hypotonic – More solutes inside membrane, water rushes in to equilibrate
concentrations and the cell swells. In our case, the potato becomes very
rigid from higher water concentration.
Hypertonic – More solutes outside the membrane, water rushes out to
equilibrate concentrations and cell shrivels. The potato becomes very flaccid
and weak.
For more information, turn to page 44 of your lab manual.
If we were to place red blood cells in a:
Hypotonic solution – water would rush in to the blood cells and burst
(hemolysis) making in possible to see through the test tube.
Hypertonic solution – water would rush out of the blood cells and shrivel
them, but not to the point that the test tube would be clear.
Isotonic solution – the cells would be in equilibrium with their surrounding
environment, causing no change and making it impossible to see through the
test tube.
For more information, refer to page 44 of your lab manual.