1. Circle the correct answer: (20 pts.)

The dehydroascorbic acid content of a sample (can or cannot) be assayed with 2,6-dichloroindophenol.

Loss of phytol from chlorophyll results in a (change in color or change in solubility).

Xanthophylls are (more or less) polar than carotenes.

Myoglobins (must be or do not need to be) extracted prior to their analysis.

Kjeldahl assay measures (protein nitrogen or all nitrogen compounds).

The Biuret method quantifies (all or only soluble) proteins.

In SDS PAGE electrophoresis, separations are based on the (charge or size) of individual proteins.

Denatured proteins are generally (less or more) soluble in water than their native counterpart.

The Bradford Dye-Binding method of quantifying proteins uses a (non-fluorescent or fluorescent) indicator.

Cis-parinaric acid binds to the (negatively charged or hydrophobic) regions of proteins.

 2. What is the difference in the assays that allows the SDS binding assay to measure total protein surface hydrophobicity and limits the use of fluorescent probes to measure only the surface hydrophobicity of soluble proteins? (6 pts.)

3. For calculating the protein content by the Kjeldahl method, the following equation is used:

        5 mLs HCL x 0.1 N HCl x 14 x 6.25 x 100           =       43.75% protein
                   1000 x 0.1 gram sample

Describe the terms in bold type and the significance of these values. (6 pts.)

4. Describe three (3) mechanisms for the separations of proteins (not involving precipitation) and give an example of an analytical technique using each mechanism. (9 pts.)

5. Explain why (or why not) a colorimetric assay for vitamin A activity would (or would not) be accurate. (6 pts.)

6. Explain the mechanism that cause proteins to precipitate during Isoelectric precipitation and the mechanism that causes precipitation with ammonium sulfate. (4 pts.)

7. Describe the spectrophotometric assay of anthocyanins. (510-540 nm). (5 pts.)

8. What is a potential problem with the precipitation of protein with ethanol? (3 pts.)

9. Briefly describe how reflectance spectrometer works and some of its uses. (6 pts.)

10. List three vitamins that can be separated by HPLC and detected with a fluorometer (either in their native states or as derivatives). What is the advantage of a fluorometer over a dioade array detector? (6 pts.)

11. Briefly write down the differences between the following items. (14 pts.)

a. Dialysis vs. Ultrafiltration

b. Metmyoglobin vs. Oxymyoglobin

c. Bioassy vs. Physiochemical vitamin assay.

d. Kjeldahl vs MacroN Analyzer

e. Biuret vs. Lowry Method of Quantifying Protein

f. Chlorophyll vs. Pheophytin

g. Vitamin A vs. Carotenes

12. While your are working as the director of quality assurance for a major food company, your "Cheeze-Whiz" product has experienced a loss in viscosity compared to the product specifications. You suspect the whey protein (a major ingredient) is the blame. You are not sure if your supplier has substituted a cheaper protein source into his product or if the protein has somehow been improperly processed (e.g., exposure to high heat). Describe the analysis your would order to answer these question about the quality of the whey protein isolate and what you would hope to learn from each assay. (15 pts.)