Summer Research Program for Science Teachers
VITAMIN C AND PROTEIN ANALYSIS
Arthur B. Geen -1997
Mentor: Howard B. Lieberman, Ph.D.
Food for thought, or rather food for the body whether it is Italian, Chinese, Indian, Spanish, Russian, ad nauseam. Food gives us the energy for everything we do in our daily lives and everything that seems beyond our control. Nerves, smooth muscle (as well as striated which is voluntary or within our control), heart, glands, etc require a source of energy. In addition food supplies the nourishing substances needed to build, repair and maintain our organs and tissues. [5-8 Content Standard C- Structure and function in living systems]
All food consists of six nutrients or nourishing substances. Carbohydrates (sugar and starch), fat, protein, vitamins, minerals, and water are the six nutrients. Protein in food can be used to supply energy but the major energy sources are carbohydrates and fats. The body uses protein and minerals to build and repair tissue. The nutrient vitamins have a twofold purpose. They aid in growth but also help to protect the body from disease.
We will concentrate on vitamins and proteins because they will be the subject of our investigations. There are approximately 13 vitamins - A, B1 ( Thiamine), B2 (Riboflavin), Niacin, B6 (Pyridoxine), Biotin, Pantothenic Acid, Folic Acid, B12 (Cobalamin), C (Ascorbic Acid), D, E (Tocopherol), K. Vitamins are generally divided into two major groups: fat - soluble and water - soluble. [5-8 Content Standard B- Properties of matter] A, D, E, and K are the fat - soluble vitamins usually associated with the lipids of natural foods. The water - soluble vitamins include C and the B complex ( i.e. Thiamine, Riboflavin, etc). If you maintain an animal on a vitamin-deficient diet it will get sick.
A lack of vitamin A can lead to dry skin, xerophthalmia (dry eyes), dry mucous membranes, retarded development and growth, sterility in male animals and night blindness. Not a pretty picture. A lack of vitamin C will cause scurvy to develop. The synthesis of connective tissue containing collagen is defective. Symptoms include swollen and bleeding gums with loosened teeth, stiffness and soreness of joints, bleeding under the skin, and slow wound healing. How is scurvy prevented? By eating citrus fruits, tomatoes, peppers, cabbage, potatoes and berries, but not necessarily in that order. [5-8 Content Standard F- Personal health] Vitamin C is probably one of the easiest vitamins to detect. It will reduce the blue dye, 2,6-dichlorophenolindophenol (indophenol) to a colorless solution. We will be making use of this reaction later on. [5-8 Content Standard B- Properties of matter]
Substances that prevent or slow down oxidation are called antioxidants. Antioxidants are used as food additives to retard spoilage and the changing of colors. Vitamin C is an antioxidant. It can prevent cell damage and other changes that oxygen causes by scavenging the oxygen free radicals. Linus Pauling winner of the Nobel chemistry award in 1954 believed in treating the common cold with large doses of vitamin C. More recently it is believed that vitamin C may play a part in restraining osteoarthritis in the knee (BRODY, 1996). Osteoarthritis is the roughening and thinning of the cartilage (meniscus) in the knee. As the disease progresses, the cartilage develops cracks and wears away eventually allowing bone to rub against bone. This results in grinding noises, pain and stiffness in the joints. Vitamin C might aid in the repair of collagen.
What do steak, chicken, salmon, trout, milk and peanuts have in common, besides containing an allotment of fat? They all contain protein. Proteins play crucial roles in almost all biological processes. Nearly all chemical reactions in the body are catalyzed ( reaction rates are speeded up) by enzymes. These enzymes are proteins. Proteins are also involved in:
1. The transport of molecules. - Hemoglobin, a protein transports oxygen in red blood cells.
2. Coordinated motion. - Muscle
3. Mechanical support. - Tensile strength of skin and bones is due to the protein collagen.
4. Immune protection. - Antibodies.
5. Generation and transmission of nerve impulses.
6. Control of growth and differentiation. - Growth factor proteins and hormones.
[5-8 Content Standard C- Structure and function in living systems]
Biuret reagent (an alkaline 0.02% copper sulfate solution) which is blue in color will react with proteins to form a purple color. [5-8 Content Standard B- Properties of matter] Another stain, Coomassie blue can also be used. Cells unfortunately contain thousands of different proteins. Two of the properties of proteins are electrical charge and size (molecular weight). Electrophoresis will separate protein based on the migration of charged particles in an electric field. This procedure uses a polyacrylamide gel which acts like a sieve to slow proteins based upon their molecular weight. The heavier the molecular weight the shorter path it will travel, the lighter the molecular weight the longer path it will travel. [Content Standard Unifying Concepts- Models and explanation]
INTEGRATION INTO THE CLASSROOM
The information from the sixth grade Life Science curriculum on foods will be incorporated into the seventh grade Physical Science unit. The first series of lessons makes use of inquiry skills: scientific method, metric system, and scientific tools. There will be a two-step approach. To begin with, students will work in groups of four to determine the vitamin C or ascorbic acid content of different orange flavored drinks ( Hi-C, Tropicana, etc). They will use all the steps of the scientific method: problem, hypothesis, experiment (materials and method), observations and conclusions. In the course of this investigation they will put their data on the blackboard to make it easier for the class to evaluate.
They will also become familiar with various pieces of apparatus ( racks, test tubes, graduated cylinders, mortar and pestle, etc) and will make use of the metric units of volume.
The second step incorporates some of the techniques developed in Dr. Lieberman's lab, on using Coomassie blue and protein separation using gel electrophoresis. The use of polyacrylamide gels in not only new to the school, its new to the seventh grade science curriculum. In experimenting with proteins the same format will be followed. What is the best source of protein in your diet? Total protein will be determined by adding Coomassie blue to a serial dilution of milk. Since the amount of protein can be gotten off the label of milk, the color change when Coomassie blue is added will be a good indication of the protein concentration of food. Gel electrophoresis will determine the number of bands of protein and their approximate size.
Below is a lab exercise on the vitamin C content of different beverages.
PROBLEM: What is the best source of vitamin C in orange flavored drinks?
MATERIALS: Indophenol solution, 25 mL graduated cylinder, 250 mL graduated cylinder, test tube rack, 5 test tubes, vitamin C tablet, mortar and pestle, stirring rod, 2 - 250 mL beakers, medicine droppers, paper cups, three different beverages containing vitamin C. [Teaching Standard D- Make accessible science tools]
1. Use a mortar and pestle to grind a vitamin C tablet into a powder.
2. Add 200 mL of water to a beaker and stir in the vitamin C powder. Label the beaker mixture A. (NOTE: MIXTURE A IS CONCENTRATED)
3. Take 20 mL of mixture A and place it in a second beaker. Add 180 mL of water to this beaker. Label the beaker mixture B. (NOTE: MIXTURE B IS DILUTE)
4. Add 10 mL of indophenol to 2 test tubes.
5. Add mixture A to one test tube containing indolphenol, one drop at a time, until the solution becomes colorless. Count the number of drops and record in the data table below.
6. Repeat step number 5 but this time use the dilute solution of vitamin C.
7. Create a new procedure in which you test each of the beverages you brought from home. In a group of four, one beverage should be brought in by each student. [5-8 Content Standard A- Design and conduct scientific investigations]
7.1 Do the procedure three times for each beverage..
7.1 Take an average of the drops you used..
7.2 Record information on your own data table.
8. Use the information on the data table to create a bar graph showing which beverage contains the most vitamin C.
NUMBER OF DROPS
CONCENTRATED - A
DILUTE - B
1. What is the color of indophenol solution?
2. Define the following terms:
2.1 Concentrated -
2.2 Dilute -
3. How many drops of the concentrated mixture of vitamin C, did it take to make the indophenol solution become colorless? Why?
4. How many drops of the dilute mixture of vitamin C, did it take to make the indophenol solution become colorless? Why? [Content Standard Unifying Concepts- Change, constancy, and measurement]
5. Below is a structural formula for a molecule of vitamin C (Ascorbic Acid.)
O OH OH H OH
C C C C C C H
H OH H
6.1 What are the elements that compose this molecule?
6.2 How many atoms of each element?
7. Submit a lab report for this experiment and include the following steps:
7.5 OBSERVATIONS - INCLUDE GRAPH
Students will work in laboratory groups of four students and use the internet to do their research. Each group will select one of the following topics (diseases involving vitamin C or protein): scurvy, kwashiorkor, pellagra, anemia, measles, mumps, chicken pox, tetanus, hay fever. One student will investigate the symptoms. The second student will inquire about the causes and where in the world it is most prevalent. The two remaining students will either write letters or use E mail to gather more information from the following sources: Center for Science in the Public Interest,Health and Human Services Department, National Institute of Child Health and Human Development, The Nutrition Information Center, U.S. Public Health Each group will then report their findings to the class. [Teaching Standard E- Nurture collaboration among students]
Brody, J.E. Research hints vitamins D and C may slow down osteoarthritis. The New York Times: 9/4 1996.
Concise Columbia Electronic Encyclopedia. Vitamins. Columbia University Press, 1994.
Harper, H.A. Review of Physiological Chemistry. California: Lange Medical Publications, 1971.
Lehninger, A.L., Nelson, D.L., and Cox, M.M. Principles of Biochemistry. New York: Worth Publishers, 1993.
Stryer, L. Biochemistry, fourth edition. New York: W. H. Freeman and Company, 1995.
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