BIOL 225 LAB FINAL Exam Questions
And All Correct Answers.
spectrophotometer - Answer An instrument that measures the proportions of light of different
wavelengths absorbed and transmitted by a pigment solution.
standard curve - Answer graph or curve generated from a series of samples of known concentration
demonstrate a relationship between known concentrations and absorbance. This relationship must be
linear over the range of the standard solutions.
chromogen - Answer a substance that becomes colored when it undergoes a chemical change
micropipettes - Answer a very fine pipette for measuring, transferring, or injecting very small quantities
of liquid.
slope of the linear trendline of a standard curve - Answer can be used to interpolate an unknown
concentration of the same substance. The equation y = mx+b is used to calculate unknown
concentrations. Note that the equation is y=mx is used when the linear trendline passes through (0, 0).
This will be the case for the standard curves prepared in this course.
Micropipette Use - Answer P10:
0.5 - 10 microL
white tips
P20:
2 - 20 microL
yellow tips
P200:
20 - 200 microL
yellow tips
, P1000:
200 - 1000 microL
blue tips
Precautions to Follow When Using Micropipettors - Answer Never rotate the volume adjustor beyond
the upper or lower range of the pipette.
Never use the micropipettor without a disposable tip in place; this could ruin the piston.
Never reuse a tip that has been used to measure a different reagent.
Never immerse the barrel of the micropipettor in fluid.
Never let the plunger snap back after withdrawing or expelling fluid.
Never invert or lay the micropipettor down with a filled tip.
Never flame the tip or the micropipettor.
Making dilutions - Answer C1V1 = C2V2
Example: You have a stock solution of protein that has a concentration of 1.25 μM, and you need 5.0 mL
of a 0.25 μM concentration. How would you make this? - Answer C1 is the initial stock concentration,
1.25 μM.C2 is the required final concentration, 0.25 μM.V2 is the final volume required, 5.0 mLSolving
for V1 = C2V2 / C1 = 0.25μM (5.0 mL) / 1.25μM = 1.0 mL
Therefore, you would add 1.0 mL of the 1.25 μM stock solution to 4.0 mL of distilled water to provide 5.0
mL of a 0.25 μM solution. (Note the number of significant figures in the answer). You can check the
answer by placing all the values in the above equation;
1/100 dilution - Answer 1 part of the solute is added to 99 parts of the diluent (not 100 parts). The
total volume is 100 parts.* Another way to express this is to say that it is a dilution of 10-2.
reduce a 1/100 dilution by a further 1/100 - Answer The total dilution is theproduct of the two
dilutions, thus:
(1/100)(1/100) = 1/10 000 or, (10-2) (10-2) = 10-4
And All Correct Answers.
spectrophotometer - Answer An instrument that measures the proportions of light of different
wavelengths absorbed and transmitted by a pigment solution.
standard curve - Answer graph or curve generated from a series of samples of known concentration
demonstrate a relationship between known concentrations and absorbance. This relationship must be
linear over the range of the standard solutions.
chromogen - Answer a substance that becomes colored when it undergoes a chemical change
micropipettes - Answer a very fine pipette for measuring, transferring, or injecting very small quantities
of liquid.
slope of the linear trendline of a standard curve - Answer can be used to interpolate an unknown
concentration of the same substance. The equation y = mx+b is used to calculate unknown
concentrations. Note that the equation is y=mx is used when the linear trendline passes through (0, 0).
This will be the case for the standard curves prepared in this course.
Micropipette Use - Answer P10:
0.5 - 10 microL
white tips
P20:
2 - 20 microL
yellow tips
P200:
20 - 200 microL
yellow tips
, P1000:
200 - 1000 microL
blue tips
Precautions to Follow When Using Micropipettors - Answer Never rotate the volume adjustor beyond
the upper or lower range of the pipette.
Never use the micropipettor without a disposable tip in place; this could ruin the piston.
Never reuse a tip that has been used to measure a different reagent.
Never immerse the barrel of the micropipettor in fluid.
Never let the plunger snap back after withdrawing or expelling fluid.
Never invert or lay the micropipettor down with a filled tip.
Never flame the tip or the micropipettor.
Making dilutions - Answer C1V1 = C2V2
Example: You have a stock solution of protein that has a concentration of 1.25 μM, and you need 5.0 mL
of a 0.25 μM concentration. How would you make this? - Answer C1 is the initial stock concentration,
1.25 μM.C2 is the required final concentration, 0.25 μM.V2 is the final volume required, 5.0 mLSolving
for V1 = C2V2 / C1 = 0.25μM (5.0 mL) / 1.25μM = 1.0 mL
Therefore, you would add 1.0 mL of the 1.25 μM stock solution to 4.0 mL of distilled water to provide 5.0
mL of a 0.25 μM solution. (Note the number of significant figures in the answer). You can check the
answer by placing all the values in the above equation;
1/100 dilution - Answer 1 part of the solute is added to 99 parts of the diluent (not 100 parts). The
total volume is 100 parts.* Another way to express this is to say that it is a dilution of 10-2.
reduce a 1/100 dilution by a further 1/100 - Answer The total dilution is theproduct of the two
dilutions, thus:
(1/100)(1/100) = 1/10 000 or, (10-2) (10-2) = 10-4
