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International Units of Measurement

Jeff Lawrence (Z30)

1. Standard units of measurement in biology are given below. This table deviates from MKS standards in that the kilogram (mass) and Kelvin (temperature) are not standard in biology.
__Measure Unit Abbr. Translation__
Number mole mol 6.022x1023
Mass gram g 454 gram È 1 pound
Length meter m .0254 meter = 1 inch; 1 m È 39 inches
Volume liter l 3.9 liters È 1 gallon
Concentration molar M 1 mole per liter
Time second s
Temperature Celsius C 1° = 9/5 F; 0° = 32 F; 100° = 212 F
Radioactivity Curie Ci 3.7x1010 disintegrations per second
Resistance (R) ohm W
Current (I) ampere amp
Voltage (V) volt V V = I*R
Power (P) watt W (V*A) P = I*V; P = I2*R

2. Units can be expressed with prefixes denoting tenfold multiples of base unit. For example, 1000 meters is 1 kilo-meter; 1000 micrograms is 1 milligram.
__Multiple Prefix Abbr.__
10-18 atto- a
10-15 femto- f
10-12 pico- p
10-9 nano- n
10-6 micro- m
10-3 milli- m
10-2 centi- c
10-1 deci- d
101 deca- D
102 hecto- H
103 kilo- k
106 mega- M
109 giga- G
1012 tera T

3. Molecular weight is expressed as grams per mol. If a substance (e.g., NaOH) has a molecular weight of, say, 40 grams per mol, a 1 M solution would contain 40 g per l, or 4 g per 100 mL, or 40 mg/ml.

4. A 1 % solution can be approximated as 1 g of solute per 100 mL or final solution, or 10 mg/ml.

Last Update: Thursday June 19 2014
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Eric Kofoid
eckofoid at ucdavis.edu