Questions to study.
1. Properties of water-soluble vitamins.
2. Structure, coenzyme forms, sources, daily requirement, and biological significance of water-soluble vitamins (В1, В2, panthotenic acid, niacin, В6, folic acid, В12, Н). Clinical manifestations of their deficiency.
Assignment for self-instruction
| | Guidelines for performing the task |
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| Study water-soluble vitamins that have coenzymes | |
| РР, В1 В2 В3 В6 В12 Н, folic acid |
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Principal dietary sources | |
Specific name of hypovitaminosis | |
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Class of enzymes containing this vitamin | |
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| Vitamin which is the base for this coenzyme | |
3. Wite down redox reactions for NAD+ and FAD.
4. Write down a reaction of thiamine pyrophosphate formation and the total equation of decarboxylation of pyruvate and α-ketoglutarate.
Ending of the table
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| | 5. Write down the reaction of synthesis of tetrahydrofolic acid (THFA) as coenzyme of folic acid. Characterize the role of THFA as carrier of one-carbon groups: write down structural fomulas of 5,10-methylene-H4-folate, 5-meth-yl-H4-folate, 10-formyl-H4-folate. 6. Write down the reaction of transamination of amino acids with participation of pyridoxal phosphate |
7. Write down the formula of coenzyme A. 8. Write down the reaction of carboxybiotin synthesis. 9. Describe the role of methylcobalamin and deoxyadenosylcobalamin in metabolic processes |
Library-research paper 1. Pernicious anemia.
LABORATORY WORK
1. Qualitative responses to water-soluble vitamins
1.1. Qualitative responses to thiamine
The product of thiamine oxidation by potassium hexacyanoferrate is yellow-colored thiochrome which shows fluorescence in the ultraviolet light:
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Procedure
5 drops of 5% K3[Fe(CN)6] (potassium hexacyanoferrate (III)) are mixed with 2-3 mg of thiamine in the test tube. Shake well the contents of the tube and heat on a burner flame. Characteristic yellow color appears. Then 1 ml of isobutyl alcohol is poured into the test tube. Shake the reaction mixture for 1 min. Transfer the upper alcohol layer with a pipette into a new test tube. This solution shows violet fluorescence in ultraviolet light.
Thiamin forms an orange colored complex with diazophenylsulphonic acid in alkaline medium.
Procedure
► 5 drops of 1% diazophenylsulphonic acid and 5 drops of 5% NaNO3 are poured into the test tube.
► Thiamin powder on the knife-tip and 5 drops of 10% NaCO3 are added.
► Stir the tube well.
Watch the emergence of orange coloration.
1.2. Qualitative response to riboflavin
Red-colored rhodoflavin forms in the process of riboflavin reduction with hydrogengas. Upon further reduction, red color disappears due to formation of colorless leucoflavin: