BSc Nursing 1 St Year Nutrition And Biochemistry Nursing Chapter 18 Composition Of Vitamins Question And Answers

Composition Of Vitamins

Question 1. Define and classify vitamins.
Answer.

Definition Of Vitamins

• Vitamins are defined as organic compounds occurring in natural foods, which are required in minute amounts for normal growth, maintenance and reproduction
• Chemically they were found to be amines and they were vital to life, hence Funk named them “vitamins”

Classification Of Vitamins

Fat-soluble Vitamins

• Vitamin A, D,E and K are know as fat or lipid – soluble vitamins.
• Their availability in the diet, absorption and transport are associated with fat.
• They are soluble in fats and oils and also the fat solvents (alcohol, acetone etc.) They are stored in the liver and adipose tissue.
  They are not readily excreted in urine. But with feceas via the enterohepatic circulation
  Excess consumption may lead to accumulation and toxic effects.

Water Soluble Vitamins

• Heterogeneous group of compounds since they differ chemically from each other.
• Common character – solubility in water.
• Readily excreted in urine and not toxic to body.
• Not stored in large quantities in the body (except vitamin B12).
• Stores depleted within weeks and deficiency symptoms results.
• Hence need to be continuously supplied through the diet.

Question 2. Write sources, daily requirement, functions and deficiency manifestation of vitamin A.
Answer.

Introduction Of Vitamin A

• Vitamin A exists in three forms
  • Vitamin A alcohol – retinol
  • Vitamin A acid – retinoic acid
  • Vitamin A aldehyde – retinal
• Vitamin A can also be formed from provitamins, known as carotenes

Daily Requirement

4000 to 5000 IU

1 IU = 0.3 micrograms of retinol

Dietary Sources

• Animal sources – liver, kidney, egg yolk, milk, cheese, butter and cod liver oil
• Vegetable sources – carotenes – carrots, spinach, pumpkins, mango and papaya

Functions Of Vitamin A

Role In Vision is main function of vitamin A

• Vitamin A is required for normal reproduction
• Vitamin A is required for epithelialization and is essential to maintain healthy epithelial tissue.
• Vitamin A is required for the construction of normal bone and teeth
• Vitamin A is required for glycoprotein synthesis
• Vitamin A is required for the synthesis of chondroitin sulfate
• Vitamin A plays a role in cell differentiation and cell division
• Vitamin A is involved in protein synthesis
• Vitamin A plays a role in DNA metabolism
• Carotenes function as antioxidants and reduce the risk of cancers initiated by free radicals

Vitamin A Deficiency

• Retinol deficiency depresses the re-synthesis of rhodopsin and interferes with the function of rods resulting in night blindness
• In Vitamin A deficiency sperm cells do not mature and in females there may be abortion.
• In Vitamin A deficiency the skin becomes dry, scaly and rough. These changes are called keratinisation.
• There is dryness of the conjunctiva and cornea, which is known as xerophthalmia.
• White opaque spots, known as Bitots spots appear on the conjunctiva.
• Cornea becomes keratinized, opaque, soft and ulcerated. This is known as keratomalacia.
• Keratinization occurs in the mucous membrane of the respiratory tract leading to increased susceptibility to infection and lowered resistance to disease.
• Vitamin A deficiency causes arrested bone development.
• The teeth become unhealthy with chalky deposits on the surface.

Read And Learn More: BSc Nursing 1st Year Nutrition And Biochemistry Previous year Question and Answers

Question 3. Describe sources, recommended daily allowance, biological functions and deficiency manifestation of vitamin D
Answer.

Vitamin D

The active form of Vitamin D is calcitriol (1, 25 di hydroxy cholecalciferol)

Daily Requirement

The daily requirement of calcitriol is 200 to 400 IU

1 IU = 0.025 micrograms of cholecalciferol

Dietary Sources

• The cheapest source is sunlight
• Fish liver oil is the richest source
• Other sources are fish, egg yolk, margarine and lard

Functions Of Vitamin D.

• Calcitriol increases the intestinal absorption of calcium and phosphorus by increasing the synthesis of calcium binding protein. This protein increases calcium absorption by the intestine.
• In the osteoblasts of the bone, calcitriol stimulates calcium uptake for deposition as calcium phosphate. Thus calcitriol is essential for bone formation.
• Calcitriol increases the reabsorption of calcium and phosphorus by the kidney and thus decreases their excretion in the urine.

Deficiency Of Vitamin D

There are 3 types of vitamin D deficiency:

• Rickets
• Osteomalacia
• Renal osteodystrophy

Rickets

• Vitamin D deficiency in children is known as rickets.
• In the absence of vitamin D the osteoblast proliferation is not accompanied by vascularization and mineralization at the normal rate.
• The bones become soft.
• Bending of long bones gives rise to deformities such as bow legs and knock knees.
• The ankles, knees, wrists and elbows are swollen.
• The fontanelles do not close properly giving rise to hot cross bun appearance of the head.
• The ribs give a beaded appearance, known as ricket rosary.
• The chest gives a pigeon breast appearance.
• Teeth erupt late and are deformed

Osteomalacia

• Vitamin D deficiency in adults is known as osteomalacia
• Osteomalacia is seen in pregnancy and lactation, when there is additional requirement of vitamin D and drainage of it in the milk
• Osteomalacia is also seen in women who observe purdah and in areas where sunshine is scanty
• In osteomalacia the bones become soft and are easily fractured
• It particularly affects the pelvic bones

Renal Osteodystrophy

• It is also known as renal rickets
• It is seen in patients with chronic renal failure
• Renal rickets is mainly due to decreased synthesis of calcitriol by the kidney
• It can be treated by the administration of calcitriol

Question 4. Functions and deficiency manifestation of vitamin C.
Answer.

Vitamin C

Vitamin C is also known as ascorbic acid

Functions Of Vitamin C

• Vitamin C is required as a coenzyme in hydroxylation of proline and lysine. Hydroxyproline and hydroxylysine are important constituents of collagen. Thus vitamin C is required for collagen synthesis
• Vitamin C is required for bone formation
• Vitamin C enhances iron absorption by keeping it in the reduced ferrous
• Vitamin C is essential for the hydroxylation of tryptophan to hydroxy tryptophan in the synthesis of serotonin
• Vitamin C is required for the oxidation of P hydroxy phenyl pyruvate to homogentisic acid in tyrosine metabolism
• Vitamin C is required for the reduction of dihydrofolate (FH2) to tetrahydrofolate (FH4). Tetrahydrofolate (FH4) is the active form of folic acid
• Vitamin C is required for the synthesis of steroid hormones
• Vitamin C is a strong antioxidant. It spares vitamin A and vitamin E from oxidation
• Vitamin C enhances the synthesis of immunoglobulins
• Vitamin C increases the phagocytic activity of leucocytes
• Vitamin C is required for the formation of mucopolysaccharides
• Vitamin C is required for the functional activity of osteoblasts and fibroblasts
• Vitamin C is required for the formation of ferritin
• Vitamin C is required for the electron transport chain
• Vitamin C activates the enzyme arginase and inhibits the enzymes urease and amylase
• Vitamin C is required as a coenzyme for the conversion of dopamine to norepinephrine
• Vitamin C is required for the formation of carnitine
• Vitamin C is required for the alpha oxidation of fatty acids
• Vitamin C plays a role in reduction of blood cholesterol level
• Vitamin C plays an important role in the reaction of the body to stress

Deficiency Of Vitamin C

• Vitamin C deficiency causes a disease called scurvy
• The capillaries are fragile and there is a tendency to haemorrhage
• The haemorrhage may be subcutaneous, subperiosteal or internal
• Wound healing is deficient due to decreased formation of collagen
• Poor teeth formation
• Gums are swollen, spongy and bleed on slightest pressure
• In severe infection there may be secondary infection, loosening and falling of teeth
• Mineralization of the bone is poor and the bones are weak and easily fractured
• Bones and joints are extremely painful
• Hypochromic microcytic anemia
• Elderly bachelors and widowers, who prepare their own food, are particularly prone to the development of vitamin C deficiency.This is called bachelor scurvy.