Ex_Appendix_A - Appendix A Measurements and Solutions Units...

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Appendix A: Measurements and Solutions Units of measure and Measuring Devices Units of Measure Commonly Used in Modern Biology In an experimental science, a system (for example, a collection of cells or components of cells) is manipulated in carefully controlled ways; the response of the system to these manipulations is observed in order to determine its properties. A quantitative science is a science in which the manipulations and observations can be measured and assigned numerical values. For example, a cell biologist might be required to measure the diameter of a particular organelle; a molecular biologist might be required to suspend a measured weight of isolated DNA in a measured volume of liquid. A complete record of a measured value must include two components: a number and a unit of measure. The metric system of units is used to record measurements and perform calculations in the biological sciences. The units listed below are especially useful in experimental biology. You should become familiar with these units and be able to convert a number expressed in one unit to a corresponding number expressed in a unit of different size. Units of length : meter ( m ) The meter is approximately equal to 39.4 inches, slightly longer than 1 yard. centimeter ( cm ) 1 cm = 10 -2 m millimeter ( mm ) 1 mm = 10 -3 m micrometer ( μm ) 1 μm = 10 -6 m nanometer ( nm ) 1 nm = 10 -9 m Angstrom ( Å ) 1 Å = 10 -10 m Temperature is measured in degrees Celsius (° C ). If a conversion from Fahrenheit temperature is required recall that: Equation 1-1 where “ n ” is the temperature in ° F .
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Appendix A: Measurements and Solutions Page 2 of 25 Units of time : hour ( h or hr ) minute ( min ) 1 min = 1/60 hr second ( s or sec ) 1 sec = 1/60 sec milliseconds ( ms or msec ) 1 msec = 10 -3 sec U nits of volume : liter ( L ) One liter is slightly larger than one quart. milliliter ( mL ) 1 mL = 10 -3 L microliter ( μL ) 1 μL = 10 -6 L Units of weight: gram ( g ) There are approximately 450 g in one pound ( lb ). milligram ( mg ) 1 mg = 10 -3 g microgram ( μg ) 1 μg = 10 -6 g The kilogram (1 kg = 10 3 g ) is also in standard use, but is too large a unit to be of practical value for most laboratory experiments in modern biology. It is usually best to express a measurement in units that give a numerical value between 0.1 and 100, preferably between 1 and 10. For example, a biological membrane might have a measured thickness of 0.0000076 mm = 0.0076 μm = 7.6 nm = 76 Å. The membrane thickness is much easier to read when expressed in units of nm or Å than when expressed in units of mm or μm . Dimensions of individual molecules and distances between atoms are often given in units of Å. Dimensions of subcellular structures which are constructed of many molecules, such as
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This note was uploaded on 05/05/2010 for the course BIO 206L taught by Professor Unknown during the Spring '08 term at University of Texas.

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Ex_Appendix_A - Appendix A Measurements and Solutions Units...

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