Vitamins

Question 1

Fat soluble Vitamins

Answer 1

Vitamins A D E and K

Question 2

Water Soluble Vitamins

Answer 2

Vitamin B complex
Niacin (Nicotinic acid or Nicotinamide)
Biotin
Folic Acid
Vitamin C

Question 3

Name the B Complex vitamins

Answer 3

1. Vitamin B1=Thiamine
2. Vitamin B2= Riboflavin
3. Vitamin B5= Pantothenic acid
4. Vitamin B6= Pyrodoxine, Pyridoxal, and Pyridoxamine.
5. Vitamin B12= Cobalamin

Question 4

Give three characteristics of water soluble vitamins.

Answer 4

1. They are soluble in water, hence, most are excreted in urine
2. They act as co-enzymes
3. Most (B-Vitamins) are essential and must be provided in diet.

Question 5

What happens if one takes high amount of water soluble vitamins?

Answer 5

They get excreted in urine when taken in excess as they are water soluble. Thus, hyper-vitaminosis may not cause toxicity.

Question 6

What is the function of Thiamine in the body?

Answer 6

Adds a pyrophosphate to Thiamine from an ATP to form a coenzyme called Thiamine pyrophosphate.

N/B: the coenzyme is necessary for the decarboxylations of alpha keto acids and transketolase.

Question 7

What are the sources of Thiamine?

Answer 7

Seeds
Nuts
Wheat
Beans
Leguminous plants
Lean meats.

Question 8

What are the functions of Riboflavin?

Answer 8

1.They are mainly used in the energy metabolism of sugars and lipids.
2. Used in the activation of FMN and FAD.

They are a major component of flavin coenzyme ie FAD and FMN

Question 9

Describe the structure of riboflavin.

Answer 9

Composed of an isoalloxazine ring system linked to ribitol.

Question 11

What are the sources of Riboflavin?

Answer 11

Meats
Nuts
Legumes
Milk
Fish
Egg

Question 12

Describe niacin

Answer 12

Not vitamins in the strictest sense as they can be synthesized from tryptophan.

Question 13

How many milligram of tryptophan is required to synthesize Niacin?

Answer 13

60mg of tryptophan is required to synthesize 1mg of Niacin.

Question 14

What are the sources of Niacin?

Answer 14

Milk
Lean meat
Unrefined grains
Cereals
Metabolism of tryptophan

Question 15

What are the three forms of vitamin B6?

Answer 15

Pyridoxine
Pyrodoxal
Pyridoxamine

Question 16

What is the function of pyridoxine phosphate as a B6 vitamin?

Answer 16

They are co-enzyme for enzymes catalyzing transaminations, decarboxylations, racemization and numerous modifications of AA side chains.

N/B. All pyridoxal phosphate-requiring enzymes act via the formation of a schiff base btwn the amino acid and co-enzyme.

Question 17

What is Biotin?

Answer 17

Biotin is a vitamin and a coenzyme commonly associated with enzymes performing carboxylation rnxs.

Question 18

What are the sources of Biotin?

Answer 18

They are normally synthesized by intestinal bacteria.

Also found in foods such as;
Liver
Egg
Vegetables
Milk

Question 19

What is Cobalamin?

Answer 19

AKA B12 vitamin and it is a complex multiple ring structure which include a cobalt atom.

Question 20

What two key rnxs are performed by Cobalamin in the body?

Answer 20

1. The rnx of methylmyonyl CoA isomers, which requires deoxyadenosyl Cobalamin.
2. Homocysteine rnx.

N/B; it is also required by RBCs during their maturation period.

Question 21

What are Pantothenic acid?

Answer 21

They forms an essential part of the acyl-carrier moiety, called Coenzyme A.

Question 22

What is the significance of Coenzyme A to the body?

Answer 22

They participate in the activation of acyl groups, including the acetyl group derived from pyruvate.

The coenzyme is derived metabolically from ATP, Pantothenic acid and beta-mercaptoethylamine.

Question 23

Source of Pantothenic acid?

Answer 23

Synthesized by some intestinal bacteria

Question 24

What is ascorbic acid?

Answer 24

AKA Vitamin C.

It is a water-soluble antioxidant that promotes the hydroxylation of proline residues of collagen.

Question 25

List 6 functions of Vitamin C to the body?

Answer 25

1. Collagen biosynthesis 2. Degradation of Tyrosine 3. Absorption of iron 4. Adrenaline synthesis 5. Bile acid formation 6. Bone mineral metabolism 7. It is a potent antioxidant. N/B; WBCs are rich in Vitamin C, which also plays an important role in immunity.

Question 26

Describe Vitamin A( subtypes )

Answer 26

Vitamin A is a generic term for a collection of 3 forms of vitamins; 1. Retinol 2. Retinal 3. Retinoic acid (Retinoids).

Question 27

What are the sources of the various subtypes of Vitamin A?

Answer 27

They exist in diet either as retinol or as Beta-carotene of which some are hydrolyzed to retinol in the intestines. Rich source of Liver, egg yolk, butter, milk are good sources of B-carotene. Leafy vegetables and some fruits provides the highest amount of B-carotene.

Question 28

Describe the visual cycle mediated by the rod cells as regulated by Vitamin A as a precursor.

Answer 28

Vitamin A is converted to its appropriate form(11-cis retinal), which acts as a visual pigment by absorbing photons in the eyes. 11-cis retinal binds with apoprotein opsin to form the visual pigment, Rhadopsin, in the rod cells. Exposure of rhadopsin to light decomposes it, which causes the dissociation of retinal and reduced to all-trans retinol. The All-trans retinol is converted back to 11-cis retinol by isomers enzyme in the absence of light. (Occurs in the cytoplasm of the rod cells) This combines with scoptosin and erhadopsin to generate another cycle of action on exposure to light.

Question 29

List 3 functions of Vitamin D in the body.

Answer 29

1. It promotes the adsorption of calcium and phosphates in the intestines. 2. It aids in the reabsoption of calcium and phosphates in the kidneys. 3. It promotes the synthesis of osteocalcin, needed for bone mineralization.

Question 30

What is Vitamin E?

Answer 30

It is a fat-soluble vitamin required in human diet and whose deficiency is rare. It's deficiency is associated with hemolytic anemia in pregnancy and newborns. It exist in the diet as a mixture of 8 closely related compounds called Tocopherols.

Question 31

List down 3 ķey functions of Vitamin E to the body.

Answer 31

1. It is an antioxidant 2. Provides protection from the action of peroxides by converting them into a product conjugating with glutamic acid and excreted in bile. 3. Acts as scavenger of free radical damage to PUFAs in cell membranes and helps prevents oxidation of LDL.

Question 32

Describe the significance of Vitamin K to the body.

Answer 32

It is the only fat-soluble vitamin that acts as a coenzyme. It is required for post translational modifications of several proteins required in the coagulation cascade. Ex. Factors 2, 7, 9 and 10. Activation is carried out by the carboxylation of specific glutamate residues on the prothrombin by a vitamin K dependent enzyme. The presence of a second carboxyl group on the glutamate side chain causes phospholipids binding properties on the prothrombin in the presence of calcium. Thus, the conversion of prothrombin to thrombin is important for clotting.