Chapter 7 Section Review Questions

1
Chapter 7 Section Review Questions
2
Sec. 7.1

• 1.) What is measured in a spectrophotometer?
• Answer A spectrophotometer measures the amount
  of light transmitted through a sample. It reports
  the percent transmittance, or the amount of light
  absorbed by the molecules in the sample,
  calculated using A2-log 10

3
Sec 7.1

• 2.) What is the difference between a UV
  spectrophotometer and a VIS spectrophotometer?
• Answer A UV spectrophotometer produces UV light
  that interacts with and detects colorless
  molecules. A visible spectrophotometer produces
  light from the visible spectrum that interacts
  with and detects molecules that exhibit color.

4
Sec 7.1

• 3.) What happens to the absorbance of a sample as
  the concentration of a sample increase or
  decreases?
• Answer Molecules do the absorbing in a sample,
  so if the number of molecules increase, the
  absorbance of the sample increases. If the number
  of molecules in a samples decreases the
  absorbance of the sample decreases.

5
Sec 7.1

• 4.) What color if light has a wavelength of
  530nm? If a molecule absorbs light at 530nm, what
  color could it be? What color do we know that it
  is not?
• Answer Green Light has a wavelength of 530nm. If
  the molecule absorbs at 530nm it could be any
  color expect green

6
Sec 7.2

• 1.) If sample has a pH of 7.8 is it considered a
  acid a base or neutral?
• Answer If a sample has a pH of 7.8 it is
  considered a base, a weak base, but a base.

7
Sec 7.2

• 2.) What does pH paper measure?
• Answer pH paper measures the H concentration
  of solution.

8
Sec 7.2

• 3.) Before pH meter can be used, it needs to be
  calibrated. To measure the pH of most solutions
  the pH meter is calibrated to what pH?
• Answer To measure the pH of most solutions the
  pH meter is calibrated to pH 7.0

9
Sec 7.2

• 4.) If the pH of a hot tub is too high, pH 8.0,
  what should be added to bring it to a neutral pH?
• Answer To bring the pH of a solution from pH 8.0
  to 7.0 add an acid.

10
Sec. 7.3

• 1.) Why must DNA and proteins be stored in a
  buffered solution?
• Answer A buffered solution resists the changes
  in pH. Protein and DNA molecules must be buffered
  to maintain their structure and function.

11
Sec 7.3

• 2.) In what kind of buffer should a DNA sample
  that was isolated from human check cells be
  stored?
• Answer A DNA sample isolated from human check
  called should be stored in a TRIS buffer.

12
Sec 7.3

• 3.) The formula weight of TRIS is 121.14g/mol.
  How is 100mL of 0.02 M of TRIS at pH 8.0
  prepared?
• Answer To prepare 100mL of 0.02 M of TRIS at pH
  8.0
• Measure 0.24g of TRIS
• 0.1 X 0.02mol/l X 121.14g/mol0.24gof TRIS
• Mix it with solvent (dH2O) to about 70mL
• Adjust the Ph to 8.0 ( with 1 M of HC1)
• Fill to a final volume of 100mL with Dh2o.

13
Sec 7.4

• 1.) What is lambda MAX and why is it important?
• Answer for particular sample, the wavelength
  that gives the highest absorbance value is the
  lambda MAX. It is the wavelength that is most
  sensitive to the proteins so it should be used
  to detect it.

14
Sec. 7.4

• 2.) What is lambda MAX for a colorless proteins?
• Answer The lambda MAX for colorless proteins is
  280nm.

15
Sec. 7.4

• 3.) How is Bradford reagents used to detect the
  presence of a specific protein in solution?
• Answer Bradford reagent cannot be used to detect
  the presence of a specific protein in solution.
  If a solution has many different proteins in it a
  Bradford protein reagent will not distinguish
  between them, An ELISA night be used to detect
  and measure the protein mixture. Or an indicator
  specific to just on protein might be used.

16
Sec. 7.4

• 4.) Which graph is used to determine the
  concentration of unknown proteins samples?
• Answer A standard curve of absorbance versus the
  concentration of known proteins can be used to
  determine the concentration of unknown samples.