Human Biology Lab Study Guide
Lab 1: Metric, Microscope and Cell Structure
1.1 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 8 of your lab manual.
1.2
Microscopy
To find differences between a compound light microscope and an electron
microscope look on page 11 of your lab manual.
Compount Light Microscopes:
1) Have glass lenses
2) Use visible light
3) Magnify up to 2,000x
4) Resolution is approximately 200 nm
Transmission Electron Microscopes
1) Use electromagnetic lenses
2) Use beam of electrons for illumination
3) Resolution is approximately 0.1 nm
4) Magnify to 1,000,000x
1.3 Use of the Compound Light Microscope
The list of microscope parts and directions for focusing the microscope are on
page 15 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.
Example: If your ocular lens is 40x and the objective lens is 100x, the overall
magnification is 40x100, or 4000x.
1.4 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.
1.5 Animal Cell Structure
A list of organelles in an animal cell is found on page 35 of your lab book.
1.6 The plasma membrane
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 38 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 39 of your lab manual.