Water Soluble Vitamins

Question 1

List the water soluble vitamins.

Answer 1

These are 2 types , the Vitamin B complex and Vitamin C.
VITAMIN B COMPLEX. These function as coenzymes in metabolic reactions and the following are the Vitamin B complex:
1. Thiamine.
2. Riboflavin
3. Niacin
4. Pyridoxine.
5. Cobalamin
6. Folic acid
7. Biotin
8. Panthothenic acid.

Question 2

Describe the chemical structure of thiamine

Answer 2

It is made up of pyrimidine and a thiazole ring

Question 3

Describe the metabolic role of thiamine

Answer 3

It is important in carbohydrate metabolism. It forms the coenzyme thiamine pyrophosphate( diphosphate) which is involved in decarboxylation reactions. It is a coenzyme in reactions catalyzed by the following enzymes:
- Pyruvate decarboxylase
It is also one of the 5 coenzymes involved in oxidative decarboxylation reactions catalysed by the following enzymes:
- Pyruvate dehydrogenase enzyme complex
- Alpha keto dehydrogenase enzyme complex.
- Branched chain amino acid dehydrogenase.
It is also involved in the Transketolase reaction in the pentose phosphate pathway

Question 4

State the recommended daily requirements and the sources of thiamine

Answer 4

Recommended daily requirements:
1mg/day
Sources
I) Animal source: liver, meat eggs.
II)Plant source: cereals, whole grains and legumes

Question 5

Describe the clinical feature due to deficiency of thiamine

Answer 5

Deficiency of thiamine causes beriberi characterized neuritis and heart failure. In chronic alcoholics thiamine deficiency causes Wernicke’s encephalopathy and Korsakoff psychosis

Question 6

Describe the chemical structure of riboflavin

Answer 6

It is made up 3 fused rings called the isoalloxazine ring which is attaches to ribitol

Question 7

Describe the metabolic role of riboflavin

Answer 7

It forms the Flavin nucleotides FMN and FAD which are coenzymes in oxidation reduction reactions. For example, FAD is a coenzyme for the reactions catalyzed by the following FAD dependent dehydrogenases:
- succinate dehydrogenase in the TCA cycle.
- Acyl dehydrogenase in the in beta oxidation
It is also one of the coenzyme in the pyruvate dehydrogenase enzyme complex and the alpha keto- glutarate dehydrogenase enzyme complex

Question 8

State the recommended daily requirements and the sources of riboflavin

Answer 8

Recommended daily requirements
2mg/day
Sources. I)Animal source: liver and kidney( organ meat).
II)Plant source: cereals, whole grains and legumes

Question 9

Describe the clinical feature due to deficiency of riboflavin

Answer 9

Riboflavin deficiency leads to angular stomatitis, dermatitis

Question 10

Describe the chemical structures of niacin

Answer 10

It is a pyrimidine 3 carboxylic acid known as nicotinic acid. The active from is nicotinamide the amide from of nicotinic acid

Question 11

Describe the metabolic role of niacin

Answer 11

It forms part of the structure NAD and NADP which are coenzymes carriers of electrons in oxidation reduction
reactions

Question 12

State the recommended daily requirements and the sources of niacin

Answer 12

Recommended Daily Requirements.
12-20mg/day
Sources:
i) Animal source: liver kidney,meat and fish
ii) Plant source: legumes. Nuts, whole grain.
Niacin can be synthesized from tryptophan.
1mg of niacin is produced from 6mg of tryptophan

Question 13

Describe the clinical feature due to deficiency of niacin

Answer 13

It causes pellagra characterized by the 3 Ds
- dermatitis
- diarrhea
- dementia
There is also the 4th D= death.
Pellagra is precipitated by a high maize diet and alcoholism

Question 14

Describe the chemical structure and metabolic roles of pyridoxine

Answer 14

Chemical structure.
Pyridoxine, pyridoxal and pyridoxal phosphate.
Metabolic role.
It forms the coenzyme pyridoxal phosphate which is involved in amino acid metabolism such as transamination and decarboxylation reactions.
It is important in heme synthesis.
It is also a coenzyme for glycogen phosphrylase

Question 15

State the recommended daily requirements and the sources of pyridoxine

Answer 15

Recommended Daily requirements
3mg/day
sources:
i). Animal source: liver kidney and muscle meat.
ii) Plant source: whole grain

Question 16

Describe the clinical feature due to deficiency of pyridoxine

Answer 16

Microcytic hypochromic anemia
Patients on the antibiotic isoniazid(INH) which is used for treatment of tuberculosis requires pyridoxine supplements the prevent the patients from developing pyridoxine deficiency. The INH forms a complex with pyridoxine and makes it unavailable for metabolic processes

Question 17

Describe the chemical structures of lipoc acid

Question 18

Describe the metabolic role of lipoic acid

Answer 18

It is one of the coenzymes involved in enzyme complexes like pyruvate dehydrogenase and alpha keto glutarate dehydrogenase

Question 19

Describe the chemical structures and metabolic role of panthothenic acid

Answer 19

Chemical structure.
It is made up of Beta alanine and pantoic acid
Metabolic role
It forms part of the structure of Coenzyme A which is a carrier of acyl groups . For example , acetate group, the fatty acyl group, succinyl group.

Question 20

State the recommended daily requirements and the sources of panthothenic acid

Answer 20

Recommended Daily requirements
10 mg/day
Sources
Found in most foods both animal and plant

Question 21

Describe the chemical structure of biotin

Question 22

Describe the metabolic role of biotin

Answer 22

It is a coenzyme in carboxylation reactions. For example in the reactions catalysed by the following enzymes;
- acetyl CoA carboxylase- in fatty acid synthesis.
- pyruvate carboxylase- in gluconeogenesis

Question 23

State the recommended daily requirements and the sources of biotin

Answer 23

Recommended Daily requirements.
25-50ug
Sources:
Animal source: live, kidney, milkand milk products
Plant source: vegetables, grains and legumes

Question 24

Describe the clinical feature due to deficiency of biotin

Answer 24

It is commonly seen in people who ingest a lot of raw egg white. Egg white contains a protein called avidin which binds biotin and makes biotin to not be available in the body.
Deficiency causes dermatitis

Question 25

Describe the chemical structure of folic acid

Answer 25

It is made up of a pteridine ring to which is attached a molecule of parabenzoic acid. And glutamate is attached to para benzoic acid

Question 26

Describe the metabolic role of folic acid

Answer 26

The active form is tetrahydrofolate which is a carrier of one carbon units such as the methyl , methylene, formly, formimino groups.
It is involved in the synthesis of the purine thymine. The enzyme id thymidylate synthetase

Question 27

State the recommended daily requirements and the sources of folic acid

Answer 27

Recommended Daily requirements
400ug
Sources:
Animal source: green leafy vegetables.
Plant source: Organ meat. muscle meat, milk

Question 28

Describe the clinical feature due to deficiency of folic acid

Answer 28

Megaloblastic anemia

Question 29

Describe the chemical structures and metabolic role of cobalamin (b12)

Answer 29

Chemical structure:n it is made up of a tetrapyrolle ring which has a cobalt ion
Metabolic role
Metabolism of odd numbered of fatty acid where propionic CoA is converted to succinly CoA.

Question 30

State the recommended daily requirements and the sources of cobalamin

Answer 30

Recommended Daily requirements
Sources
Animal source only. Organ meat, muscle meat, eggs, milk and dairy products

Question 31

Describe the clinical feature due to deficiency of cobalamin

Answer 31

Pernicious anemia. Vegetarians are advised to increase the intake of eggs and milk. This is due to effect of B12 on folate metabolism.
Homocysteine+ Methy THF→Methionine+ THF. This reaction requires vitamin B12. Deficiency of Vitamin B12 makes the THF not to be available to the body in what is called the “ Folate trap”.
Neuritis-( feeling of pins and needles) due to accumulation of methyl malonyl CoA in the myelin sheath