Biochemistry Vitamins Essay Questions And Answers

Vitamins

Question 1. Classify vitamins. Indicate dietary sources, daily requirements & deficiency of fat-soluble vitamins, Briefly explain the role of vitamin A In the vision (or) Give the sources, functions & deficiency symptoms of vitamin A. (or) Vitamin A deficiency.
Answer:

Vitamins:

Classification:

• Vitamins are classified into

Read And Learn More: BDS Previous Examination Question And Answers

1. Fat Soluble Vitamins
   • Vitamin A
   • Vitamin D
   • Vitamin E
   • Vitamin k
2. Water-soluble vitamins
   1. Vitamin B
      • Energy releasing vitamins
      • B1- Thiamine
      • B2- Riboflavin
      • B3- Niacin
      • B6- Pyridoxine
      • 7- Biotin
      • Pantothenic acid
   2. Hemopoietic vitamins
      • B12- Cyanocobalamin
      • Folic acid

Fat Soluble Vitamins:

1. Role of vitamin A in vision:
   • Retinol and retinal k retinoic acid are forms of vitamin A
   • Retinal takes part in a visual cycle called Rhodopsin Cycle or Wald’s visual cycle
   • In this cycle, initially on exposure to light isomer/atum of 11 I is-retinal to aII Irate, retinal occurs
   • All trans-retinal is immediately isomer/ed to 11 cis-retinal
   • This combines with opsin k forms Rhodopsin
   • Most of the all-trans-retinal is the transporter to liver
   • It is converted to all trans-retinol by alcohol dehydrogenase
   • All trans-retinol is isomerized to 11-cis-retinol
   • This is oxidized to 11-cis-retinal by alcohol dehydrogenase
   • Now this re-enters into the visual cycle

Question 2. Enumerate the functions of vitamin D. Explain its importance in calcium metabolism 
Answer:

Functions of vitamin D:

• Calcitriol (1,25-dihydroxycholecalciferol) is the active form of vitamin D
• Its functions are as follows:
  1. Increases intestinal absorption of calcium & phosphate
  2. Essential for bone formation
  3. Minimizes excretion of calcium & phosphate

Importance in calcium metabolism:

In the intestine, Calcitriol binds with a systolic receptor & forms a Calcitriol-receptor complex.
↓
This enters the nucleus & interacts with DNA
↓
This induces the synthesis of calcium-binding protein
↓
This increases calcium absorption by the intestine
↓
This increases calcium level

• It also promotes calcification & remodeling of bone
• It increases the mobilization of calcium & phosphate from bone

Question 3. Describe the formation of the active form of vitamin D. Describe its biochemical functions, deficiency features & daily requirements.
Answer:

Formation of the active form of vitamin D:

• Calcitriol also called 1,25-dihydroxycholecalciferol is the active form of vitamin D
• Its synthesis requires Cytochrome, NADPH & molecular oxygen

Deficiency:

• Vitamin D deficiency causes rickets in children & Osteomalacia in adults
• Features of it are as under:

Daily requirements:

• The daily requirement of vitamin D is 400 IU

Question 4. Give an account of the sources, metabolic functions, daily requirements & deficiency manifestation of vitamin C.
Answer:

Vitamin C:

Sources:

• Citrus fruits- Gooseberry, guava
• Green vegetables
• Tomatoes & Potatoes

Functions:

1. Role in collagen formation

• It acts as a coenzyme in the hydroxylation of proline & lysine
• These are required to convert procollagen to collagen

2. It is required for bone formation

3. Role in metabolism

1. Iron metabolism
   • It enhances iron absorption
   • Helps in tire formation of ferritin
   • Helps in the mobilization of iron from ferritin
2. Hemoglobin metabolism
   • It is used to reconvert methemoglobin to hemoglobin
   • Required for degradation of hemoglobin to bile pigments
3. Tryptophan metabolism
   • Essential for hydroxylation of Trytophan to hydroxytryptophan
4. Tyrosine metabolism
   • Required for oxidation of p-hydroxy phenylpyruvate to homogentisate acid
5. Polic acid metabolism
   • Required for the formation of tetrahydrofolate, an active form of folic acid

4. Hormonal functions

• Peptides are derived from glycine
• Vitamin C is required for the hydroxylation of glycine
• It is required for the synthesis of steroids hormones
• It is a strong antioxidant

5. It enhances the synthesis of immunoglobulin
6. Preventive functions
7. It prevents the risk of

• Cataract
• Cancer
• Coronary heart diseases

Daily requirements:

• The daily requirement of vitamin C is 60-70 mg

Deficiency manifestations:

• A deficiency of vitamin C leads to scurvy

Features of scurvy:

• Spongy & sore gums
• Loose teeth n Anemia
• Swollen joints
• Fragile blood vessels
• Decreased immunocompetence
• Delayed wound healing
• Impaired hormonal functions of adrenal cortex & gonads B Hemorrhage
• Osteoporosis

Question 5. Name important vitamins which are required for the proper functioning of nerves. Describe the sources, requirements, biochemical functions & deficiency manifestation of any one (or) Explain the role of thiamine (or) Deficiency manifestation of thiamine.
Answer:

Vitamins required for neurological functions:

• Vitamins necessary for neurological functions are

1. Thiamine, Vitamin B1
2. Pyridoxine, Vitamin B6

Thiamine, vitamin B1:

Sources:

1. Plant sources

• Cereals, Pulses, oil seeds, nuts & yeast

2. Animal sources

• Pork, liver, heart, kidney, milk, etc

Requirements:

• The daily requirement of Thiamine is

1. Adults-1-1.5 mg/day
2. Children- 0.7-1.2 mg/ day

Functions:

• Thiamine pyrophosphatase, TPP, a Coenzyme of Thiamine is required in the transmission of nerve impulses.
• It is required for following enzyme activity

1. Pyruvate dehydrogenase to convert pyruvate to acetyl CoA
   • Alpha-ketoglutarate dehydrogenase
   • Used in the TCA cycle
2. Transketolase
   • Utilized in hexose monophosphate shunt
3. Branched-chain alpha-keto acid dehydrogenase

• • Used to catalyze oxidative Decarboxylation of branched-chain amino acids

Deficiency manifestations:

A deficiency of Thiamine results in beri beri

Symptoms:

• Loss of appetite
• Weakness
• Constipation
• Nausea
• Mental depression
• Peripheral neuropathy
• Irritability
• Numbness in the legs

Types:

1. Wet Beri Beri
   • Characterized by edema of legs, face, trunk & sere us cavities
2. Dry beri beri
   • Associated with neurological manifestations
3. Infantile Beri Beri
   • Seen in infants

Question 6. Name the water-soluble vitamins, and describe any one of them.
Answer:

Water soluble vitamins:

1. Vitamin B:

• Energy releasing trains

1. B1 – Thiamine
2. B2 – Riboflavin
3. B3 – Niacin
4. B6 – Pyridoxinr
5. B7 – Biotin
6. Pantothenic acid

• Hemopoietic vitamins

1. B12 – cyanocobalamin
2. Folic acid

2. Vitamin C:

• Sources

1. Citrus fruits
2. Green vegetables
3. Tomatoes and potatoes

• Functions
• Required to convert procollagen to collagen
• Required for bone formation
• Help in iron, hemoglobin, tryptophan, tyrosine, and folic acid metabolism
• Required for hydroxylation of glycine
• Required for synthesis of steroid hormones
• Act as a strong antioxidant
• Enhance the synthesis of immunoglobulin

Daily requirements – 60-70 mg:

Deficiency manifestation – scurvy:

• Spongy and sore gums
• Loose teeth
• Anaemia
• Swollen joints
• Fragile blood vessels
• Decreased immunocompetence
• Delayed wound healing
• The impaired hormonal function of the adrenal cortex and gonads
• Hemorrhage
• Osteoporosis

Question 7. Biological functions of Vitamin A 
Answer:

• Retinol, retinal & retinoic acid are forms of vitamin A
• These forms perform various functions

1. Role in vision
   • Vitamin A is required for vision
   • The retinal, form of vitamin A is linked to the amino group of lysine of opsin
   • This forms Rhodopsin
   • Rhodopsin is used in the visual cycle
2. Hormonal functions
   • Retinol & retinoic acid acts as steroid hormones
   • These regulate protein synthesis
   • They are involved in cellular growth & differentiation
3. It maintains healthy epithelial tissue
   1. Synthetic functions
      • Certain glycoproteins
      • Retinol synthesizes retinyl phosphate
      • This is required for glycoproteins synthesis
   2. Transferrin
      • Retinol & retinoic acid are involved in its synthesis
   3. Cholesterol
      • Vitamin A is required for its synthesis
4. Immunological functions
   • Vitamin A maintains a proper immune system
5. Antioxidant
   • Carotenoids function as an antioxidant & reduce the risk of cancer

Question 8. Visual cycle 
Answer:

Synonyms:

• Rhodopsin cycle or Wald’s visual cycle

Visual Cycle:

• In this cycle, initially on exposure to lip, high isomerization of 11 cis-retinal lo all Irans-regional occurs
• All Irans-retinal is immediately isomerized lo 11-cis-retinal
• This combines with opsin & forms Rhodopsin
• Most of all Irans-retinal is transported to liver
• It is converted to all Irans-retinol by alcohol dehydrogenase
• All trans-retinol is isomerized lo 1 l-cis-retinol
• This is oxidized lo 11-cis-retinal by alcohol dehydrogenase
• Now this re-enters into the visual cycle

Question 9. How does vitamin K take part in the coagulation of blood?
Answer:

• Vitamin K causes post-translational
• It acts as a coenzyme for the carboxylation of glutamic acid residues present in proteins by the carboxylase enzyme
• This converts glutamate to gamma carboxyglutamate
• Gamma carboxyglutamate is negatively charged
• It combines with positively charged calcium ions to form a complex
• This complex binds to the phospholipids on the surface membrane of platelets
• This increases the conversion of prothrombin to thrombin
• This helps in blood clotting

Question 10. Vitamin K
Answer:

• It is a fat-soluble vitamin

Sources:

Vitamin K

1. Animals sources
   • Egg yolk, meat, liver, cheese & dairy products
2. Plant sources
   • Cabbage, cauliflower, tomatoes, alfa, spinach

Functions:

• It helps in blood coagulation

Daily requirements:

• 70-140 microgram/ day Deficiency symptoms:
• Diminished blood clotting
• Increased prothrombin time

Question 11. Coenzymes forms & deficiency of niacin
Answer:

Coenzymes forms of niacin:

• Nicotinamide adenine dinucleotide, NAD+
• Nicotinamide adenine dinucleotide phosphate, NADP+

Deficiency symptoms of niacin:

1. A deficiency of niacin causes pellagra
2. Its symptoms are referred to as 3Ds
3. D- Dermatitis
   • It is inflammation of the skin
   • It is found in the areas of the skin that are exposed to sunlight
4. D- Diarrhea
   • It is in the form of loose stools
   • Prolonged diarrhea leads to weight loss
5. D- Dementia
   • Associated with degeneration of nervous tissue
   • It includes:
6. Anxiety
7. Irritability
8. Poor memory
9. Insomnia

Question 12. Niacin.
Answer:

• It is vitamin B3
• It is pyridine derivative Coenzymes forms of niacin:
• Nicotinamide adenine dinucleotide, NAD+
• Nicotinamide adenine dinucleotide phosphate, NADP+

Functions:

• Coenzymes of niacin are involved in oxidation-reduction reactions
• They participate in almost all the metabolism Deficiency symptoms of niacin:
• A deficiency of niacin causes pellagra

Question 13. Name Coenzymes of niacin, Riboflavin, Pyridoxine & thiamine 
Answer:

Coenzymes of:

1. Niacin
   • Nicotinamide adenine dinucleotide, NAD+
   • Nicotinamide adenine dinucleotide phosphate, NADP+
2. Riboflavin
   • Flavin mononucleotide, FMN
   • Flavin adenine dinucleotide, FAD
3. Pyridoxine
   • Pyridoxal phosphate, PLP
4. Thiamine
   • Thiamine pyrophosphate, TPP

Question 14. Biological functions of pyridoxine
Answer:

1. The Coenzyme of Pyridoxine, Pyridoxal phosphate, PLP, is attached to the delta amino group of lysine
2. It participates in reactions like
   1. Transamination
      • It converts amino acids to keto acids – These keto acids enter the TCA cycle & generates energy
      • PLP interacts with amino acids to form Schiff base
   2. Decarboxylation
      • Many amines are synthesized by PLP Decarboxylation
      • They are:
      • Serotonin
      • Histamine
      • Gamma amino butyric acid
      • Catecholamines
   3. Deamination
      • The Hydroxyl group-containing amino acids require PLP
   4. Transsulfuration
      • It involves the transfer of sulfur from homocysteine to serine
      • It requires PLP-dependent cystathionine synthase
3. Synthetic functions
   • Synthesis of niacin Coenzymes from tryptophan
   • Synthesis of serine from glycine
4. Glycogen phosphorylase contains PLP
5. It is needed for the intestinal absorption of amino acids
6. 6. It prevents urinary stone formation

Question 15. Vitamin B12.
Answer:

It is cyanocobalamine

Coenzyme forms:

• 5′- Deoxyadenosyl cobalamin
• Methylcobalamin

Functions:

1. Synthesis of methionine from homocysteine
   • Vitamin B12 is used as Methylcobalamin in this reaction
2. Isomerization of methylmalonic CoA to succinyl CoA
   • It occurs in the presence of vitamin B12 Coenzyme, deoxyadenosine cobalamin

Dietary requirements:

• Adults- 3 micrograms/ day
• Children-0.5-1.5 microgram/day
• During pregnancy & lactation- 4 micrograms/ day

Deficiency symptoms:

• A deficiency of vitamin B12 leads to
• Pernicious anemia
• characterized by low hemoglobin levels, decreased number of erythrocytes & neurological manifestations
• Neuronal degeneration
• Demyelination of the nervous system

Question 16. Riboflavin deficiency 
Answer:

1. Riboflavin deficiency symptoms include
   1. Cheilosis
      • Presence of fissures at the comer of the mouth
   2. Glossitis
      • Tongue appears smooth & purplish
   3. Dermatitis

Question 17. Synthesis of thyroxine 
Answer: 

• Thyroxine is a thyroid hormone
• It is synthesized from the tyrosine residues of the protein thyroglobulin & activated iodine
• The tyrosine of thyroglobulin is first iodinated at position 3 to form monoiodotyrosine
• Next, it is iodinated at position 5 to form diiodotyrosine
• Later two molecules of diiodotyrosine couple to form thyroxine T4
• As the process of iodination is completed, each molecule of thyroglobulin contains about 6-8 molecules of thyroxine

Question 18. Mechanism of action of vit D 
Answer:

1. Action on the intestine

In intestinal cells, calcitriol binds with cytosolic receptors
↓
Forms calcitriol – receptor complex
↓
Complex enters the nucleus of the cell
↓
Interacts with DNA
↓
This leads to the synthesis of calcium-binding protein
↓
This protein increases calcium uptake by the intestine

2. Action on bones

• Increases calcium deposition in osteoblasts

3. Action on kidneys

• Minimizes excretion of calcium and phosphorous

Question 19. Give an account of the chemistry, sources, and dietary functions of folic acid.
Answer:

Folic acid:

Chemistry

• Consists of
• Pteridine ring
• p-amino benzoic ring (PABA)
• Glutamic acid
• Has one glutamic acid residue known as pleural-glutamic acid
• The active form is tetrahydrofolate
• Dihydrofolate reductase → folic acid → tetrahydrofolate
• H+ atoms are present at position 5,6,7 & 8 of tetrahydrofolate

Sources

• Found in abundant in leafy vegetables

Dietary functions

• Involved in the synthesis of 1 C metabolism like
• Purine
• Pyrimidine nucleotide
• Glycine, serine, ethanolamine, choline
• N – formylmethionine

Question 20. Write coenzyme form, one function, and one deficiency disorder of the following

1. Thiamine
2. Niacin
3. Ascorbic acid
4. Folic acid
5. Riboflavin 

Answer:

Question 21. Describe the functions of thiamine
Answer:

Functions of Thiamine:

• Thiamine pyrophosphatase, TPP, a Coenzyme of Thiamine is required in the transmission of nerve impulse
• It is required for following enzyme activity
  • Pyruvate dehydrogenase to convert pyruvate to acetyl CoA
  • Alpha-ketoglutarate dehydrogenase
    • Used in the TCA cycle
• Transketolase
  • Utilized in hexose monophosphate shunt
• Branches chain alpha-keto acid dehydrogenase
  • Used to catalyze the oxidative decarboxylation of branched-chain amino acids

Question 22. Fat-soluble vitamins
Answer:

Vitamins A, D, E & K are fat-soluble vitamins

Properties:

• Their availability in diet, absorption & transport is associated with fat
• They are soluble in fats & oils & in fat solvents
• They are stored in the liver & adipose tissues
• They are not readily excreted in urine
• They are isoprenoid compounds
• They have a variety of functions

Question 23. List four features of vitamin A deficiency
Answer:

• Features of vitamin A deficiency are

1. Night blindness
2. Xerophthalmia
3. Keratomalacia
4. Retarded growth

Question 24. Vitamin D 
Answer:

1. It is a fat-soluble vitamin
2. It resembles sterols in structure
3. Its best source is sunlight
4. Its active form is calcitriol
5. It is involved in calcium metabolism
6. Required in bone formation
7. Its daily requirement is 400IU
8. Its deficiency leads to rickets in children & osteomalacia in adults

Question 25. Pellagra 
Answer:

1. A deficiency of niacin causes pellagra
2. It is referred to as 3D disease
3. D- Dermatitis
   • It is inflammation of the skin
   • It is found in the areas of the skin that are exposed to sunlight
4. D- Diarrhea
   • It is in the form of loose stools
   • Prolonged diarrhea leads to weight loss
5. D- Dementia
   • Associated with degeneration of nervous tissue
   • It includes:
     • Anxiety
     • Irritability
     • Poor memory
     • Insomnia

Question 26. Vitamin C 
Answer:

• It is water soluble vitamin
• It plays an important role in human health & disease
• It is readily absorbed by the intestines & excreted in urine
• About 60-70 mg of vitamin C is required per day
• Citrus fruits are main sources of vitamin C
• Its deficiency leads to scurvy

Question 27. Coenzymes of Riboflavin & niacin 
Answer:

Question 28. What are the diseases caused by deficiency of Niacin & Vitamin B12 
Answer:

Question 29. Importance of folic acid in the diet
Answer:

• Folic acid is important in one-carbon metabolism
• The Coenzyme of it, tetrahydrofolate( THF), serves as an acceptor or donor of one carbon units
• It is involved in the synthesis of important compounds like

Question 30. Source & functions of vitamin B12
Answer:

Sources:

• Liver, kidney, milk, curd, eggs, fish, pork & chicken

Functions:

1. Synthesis of methionine from homocysteine
   • Vitamin B12 is used as Methylcobalamin in this reaction
2. Isomerization of methylmalonic CoA to succinyl CoA
   • It occurs in the presence of vitamin B12 Coenzyme, deoxyadenosine cobalamin

Question 31. Name the vitamins necessary for neurological functions 
Answer:

• Vitamins necessary for neurological fun lions are

1. Thiamine, Vitamin HI
2. Pyridoxine, Vitamin H6

Question 32. Name the Coenzymes of vitamin Bl, B6 
Answer:

Question 33. Name hemopoietic vitamins 
Answer:

• Hemopoietic vitamins are

1. Folic acid
2. Vitamin B12

Question 34. Functions of cyanocobalamine 
Answer:

• Synthesis of methionine from homocysteine
  • Cyanocobalamine is used as methylcobalamin in this reaction\
• Isomerization of methylmalonic CoA to succinyl Co A
  • It occurs in the presence of the coenzyme deovyadenosyl cobiaum

Question 35. Ascorbic acid deficiency / Scurvy
Answer:

• A deficiency of ascorbic acid leads to scurvy

Features:

• Spongy and sore gums Loose teeth
• Anaemia
• Swollen joints
• Fragile blood vessels
• Decreased immunocompetence
• Delayed wound healing
• Impaired hormonal functions of adrenal cortex and gonads
• Hemorrhage
• Osteoporosis

Question 36. Provitamins 
Answer: It is a substance that may be converted within the body into a vitamin

It is a substance with little or no vitamin activity but can be converted to an active form by normal metabolic processes

Example:

• Provitamin B5 is panthenol which may be converted in the body to vitamin B5
• Provitamin A is (3 carotenes, the body uses an enzyme to convert it to retinol

Question 37. Name the vitamin which has antioxidant properties.
Answer:

Vitamins having antioxidant properties are:

• Vitamin E
• Vitamin C

Question 38. What are the different types and features of beriberi?
Answer:

Question 39. Name a vitamin that acts as an antioxidant (or) Name a vitamin that acts as a steroid hormone 
Answer:

• Vitamin as an antioxidant – vitamin E and vitamin C
• Vitamin as steroid hormone – vitamin D

Question 40. Rickets 
Answer:

• Vitamin D deficiency causes Rickets in children
• Features:
• Bone deformities
• Incomplete bone mineralization
• Bones become soft
• Teeth formation is delayed
• Bowed legs
• Decreased plasma level of calcitriol
• Elevated alkaline phosphatase activity