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Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Research Assistant Wanted

Brother Gregory wants you to help him find the answers to questions about carbohydrate samples extracted from various parts of the Mummy of the Pharaoh Horemheb. In these investigations you will be provided with samples of material taken from various places on the mummy. You will be asked to find out what is in these samples, and then record this information for later analysis.

First, print out your personal investigation page (below) and find out which specimens you are supposed to investigate and analyze. Carry out the experiment, gather and record your data, analyze your results and write down the appropriate numbers on your personal investigation page.

This is important. Bring your completed investigation page to the examination, if it is required on your topic schedule.




Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
The Problem

Specimens of unknown materials have been taken from an Egyptian mummy. It is hoped that they will give some clues as to who or what killed the Pharaoh Horemheb.

One clue will be the chemical nature of the samples found in these specimens. Ancient Egyptians treasured and used a lot of different carbohydrates in their food and in their religious services. They also incorporated all kinds of foods and valuable sweeteners into the Mummies as they were being prepared for burial. But what kinds?

Some kinds of carbohydrates are simple sugars, others are complex polysaccharides. Each type has its own physical and chemical properties. The problem is to devise a series of tests, called qualitative assays, which can be used to test for each of these properties in turn. By carrying our a series of these assays, and comparing the results with those found by assaying known sugars and carbohydrates, it should be possible to determine which of the samples taken from the Mummy contain which kind of carbohydrate.

Qualitative assays tell you what kind of substance is there. It does not tell you how much.




Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
The Method(s)

The methods you will use in this investigation are a series of qualitative assays, or tests, for the chemical properties of carbohydrates. Each assay tests for a specific chemical or physical property such as "solubility in water" or "does it have a -CHO (aldehyde) group". Each assay is unique for that property.

Saccharides which have that property give a positive reaction with that reagent(s), whereas those saccharides that do not have that property give a negative, or no reaction with that reagent or test.

For example; Barfoed's Reagent will produce an orange to red precipitate when mixed with and reacted with solution containing a monosaccharide. It will not have any reaction with polysaccharides.

If an unknown sample is treated with Barfoed's Reagent, therefore, and no precipitate is produced, the scientist can be reasonably sure that the sample does not contain glucose, or ribose (both simple, single sugars), but may contain maltose (a di-saccharide) or starch (a polysaccharide). More tests will be needed to find out which, but one type of saccharide has now been ruled out!


a positive reaction with Barfoed's Reagent

The following are the qualitative assays you will need to use in this investigation. Check them out.

Barfoed's Reagent
a test for monosaccharides

Bial's Reagent
a test for a pentose sugar

Tollen's Reagent
a test for reducing sugar

Benedict's Reagent
a test for reducing sugar

Benedict's Reagent
a test for reducing sugar

Seliwanoff's Reactent
a test for ketoses

Amylase digestion
a test for starch

Iodine
a test for starch

Solubility
dissolves in water

Fermentation
yeast will ferment


Step One:
Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Testing known substances

As the first step in this investigation, it is necessary to understand how "known substances"behave when treated with all these reagents and assays. The results you get will be of great value later when the same assays are performed on your specimens.

You have been provided with the following "known" saccharides. In the first step of your investigation you should first read all about them and list their properties (e.g. - "a monosaccharide that is also a reducing sugar"). You should keep this table with you as you move onto testing the unknown substances from the Mummy of Horemheb.

Known Saccharides

Fructose

Galactose

Glucose

Lactose

Xylose

Maltose

Ribose

Sorbose

Sucose

Reducing Sugar

Once you know the basic chemical and physical properties of each known carbohydrate, you must test each one of the "knowns" with each of the qualitative assays listed above. Once again it is necessary to record your results in the form of an easily read table that you will be able to consult later.

Procedure:

  1. Use the Assay Bench
    Qualitative Carbohydrate Assays
    to test all the known saccharides in the table above.
  2. You will see a list of the known substances at the top and a list of the unknown specimens underneath. Click on one of the known specimens.
  3. Now choose one of the assays.
  4. Click on the "---***Start the Analysis***---" button. Two things will happen all at once - (i) your sample before it reacts appears on the left - (ii) the result of the assay will appear on the right.

Carefully record all the results you obtain from each of the assays with each of the samples. Printout and use this table to organize your findings:

Results:
Qualitative Assays of Known Saccharides


Step Two:

Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Testing the Unknowns

As the second step in this investigation you are now going to compare the results you have just obtained with the known carbohydrates with the results you get from testing the unknown specimens taken from the Mummy of Horemheb.

Before you begin - read about these specimens and find out where they were found and some of their physical properties.

Specimens collected from the Mummy

Next - print out your "Personal Research Investigation" (below) and finding out which of the samples you should be testing. Don't forget to write your answers on this paper and bring it to the appropriate examination.

  1. Use the Assay Bench
    Qualitative Carbohydrate Assays
    to test all the specimens.

  2. You will see a list of the known substances at the top and a list of the unknown specimens underneath. Click on one unknown specimen category (from your Personal Research Investigation assignment).

  3. Now choose one of the assays.

  4. Click on the "---***Start the Analysis***---" button. Two things will happen all at once - (i) your sample before it reacts appears on the left - (ii) the result of the assay will appear on the right.

Carefully record all the results you obtain from each of the assays with each of the samples and specimens. Printout and use this table to organize your findings:

Results:
Qualitative Assays of Unknown Specimens


Step Three:

Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Comparison of Results

As the third step in this investigation you will now compare the results you obtained by assaying the known carbohydrates with those of the samples taken from the Mummy of Horemheb.

This evidence may help you to find out what killed the Pharaoh - but you never know!

Procedure:
  1. Use the two sets of Results (obtained above).
  2. For each unknown specimen look along each row of assay results. Compare the assays that gave a positive result for the "known" saccharide with those that gave a positive result with the unknown specimen.
  3. You are looking for a pattern; which knowns and unknowns give the same positive and negative results.
  4. When you think you have an identical pattern - write down the name of the known saccharide as a possible component in the unknown specimen.
  5. CARE! There may be more than one kind of saccharide in the unknown specimen you are testing. The Egyptians may have been using mixtures of substances while preparing their Mummies.

Step Four:
Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Deduction

You must now deduce the chemical nature of the unknown specimens take from the Mummy. You must then try to identify what the original specimen might have been. To help you do this, there is a chart below which lists all kinds of materials found in previous Mummies, and some of their properties and contents.

First, using all the results and comparisons obtained above it is time to deduce what was the chemical nature (what kind of saccharides) were in the substances were found in the Mummy of Horemhab.

For each of your assigned specimens, try to deduce what type and kind of saccharide was in the sample you were testing. Beware! Some samples may have been a pure substance, but others may not - you don't know.

When you think you have an answer, use your new knowledge of what was in your specimens and compare them to the descriptions of other materials and substances that have been found in other Mummies (see below).

When you think you have identified your unknown specimens use the Carb numbers (Carb #) assigned to each possible material to fill in your required Personal Investigation Page (below), which you should have already printed out. Take the completed Investigation Page - with your answers - to the appropriate examination for grading.

Materials Found in Other Mummies

Material Constituents Carb #
Petals mix of cellulose, simple sugars, dyes 234
Honey di-saccharide sucrose 521
Cellulose insoluble polymer of glucose molecules 845
Starch soluble polymer of glucose molecules 664
Stems lignified materials, mostly cellulose 762
Wood hemicellulose - a polymer of xylose 113
Roots mostly inulin - polymer of fructose 422
Syrup made from corn - mostly glucose 339


Print out your
personal investigation page

Page Items
* Research Assistants
* The Problem
* The Method(s)
* Knowns
* Unknowns
* Comparison
* Deduction
* Personal Investigation
Carefully enter your Seat Number or PCIN number
(e.g.
MM34, or MA56, or WA41)
in the box below, click, and print out the page that appears.

Find the answers to the questions, write your answers on the investigation page, and bring the completed assignment to the exam for grading purposes.


Personal Investigation Page

Enter your seat number or PCIN number here: -



Science@a Distance
© 2004, Professor John Blamire