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PHA Vitamins > Fat Soluble Vitamins - A > Flashcards

Fat Soluble Vitamins - A Flashcards

1
Q

Hippocrates at about 500 B.C. cured night

blindness with…

A

…his prescription of ox liver in honey, now known to contain high Vitamin A content.

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2
Q

Vitamin A in animal food a.

animals

A

Pre-formed, such as Retinol

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3
Q

Vitamin A in plant food

A

Pro-formed such as carotenoids (the only

source for vegans)

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4
Q

Structure of Vitamin A

A

It contains a single 6-membered ring to which is attached an 11-carbon side chain.

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5
Q

Forms of retinol

A

Retinol (alcohol form of vitamin A)
Retinal (vitamin A aldehyde):
Retinoic acid (acid form of vitamin A):
Produced by retinal oxidation.

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6
Q

Retinal is obtained by…

A

…oxidation of retinol.

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7
Q

Which forms of retinol are interconvertible?

A

Retinal and retinol

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8
Q

Retinoic acid is produced by…

A

…oxidation of retinal

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9
Q

Beta-Carotene is referred to as…

A

provitamin A

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10
Q

What do pre-formed and pro-formed vitamins mean?

A

Pre-formed: Ready for activity

Pro-formed: Has to be converted first

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11
Q

Beta-Carotene: Pre-formed or pro-formed?

A

Pro-formed

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12
Q

Journey of beta-carotene in the body

A

It is sourced from plant foods and is cleaved in the intestine to produce two molecules of retinal, which is then reduced to retinol by retinaldehyde reductase in the intestines

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13
Q

Compare retinol to beta-carotene

A

It possesses only about one-sixth vitamin A activity when compared to retinol.

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14
Q

Plant sources of Vitamin A

A

Potatoes, Carrots, Dark green leafy vegetables, Palm oil, Pink Grapefruit, Fruits, Spinach

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15
Q

Animal sources of Vitamin A

A

Chicken liver, Cod liver oil, Fish oil, Eggs, Fish, Shellfish
Butter/Margarine/Cheese, Milk

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16
Q

Recommended daily intake of Vitamin A in Men

A

750 μg

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17
Q

Recommended daily intake of Vitamin A in Women

A

600 μg

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18
Q

Recommended daily intake of Vitamin A in Women during pregnancy and lactation

A

950 μg

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19
Q

Recommended daily intake of Vitamin A in infants

A

350 μg

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20
Q

Recommended daily intake of Vitamin A in children

A

600 μg

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21
Q

Physiological functions of Vitamin A

A
  • Vision
  • Growth
  • Reproduction
  • Resistance to infectious disease
  • Epithelial cell integrity
  • Bone remodeling
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22
Q

Role of Vitamin A in vision

A

Retinal is an important structural component of

rhodopsin, the light sensitive pigment within the rod and cone cells of the retina.

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23
Q

Difference between rod and cone cells of the eye

A

Rods are involved in dim light
vision while cones are responsible for
bright light & colour vision

24
Q

Role of Vitamin A in epithelial cell integrity

A
  • For proper differentiation and maintenance.
  • Lack of vitamin A leads keratinized and scaly skin because mucus secretion of secreting epithelial cells is
    suppressed
25
Q

Role of Vitamin A in reproduction

A

It is required for:

  • spermatogenesis in males
  • normal reproductive cycle in female
  • retinol and RA for embryonic development,
26
Q

Which Vitamin A form has been found to regulate gene expression for growth hormone?

A

Retinoic Acid

27
Q

Role of Vitamin A in bone remodelling

A

Normal functioning of osteoblasts and osteoclasts

28
Q

Role of Vitamin A in immunity

A

It decreases the frequency and severity of infectious disease, e.g. measles

29
Q

Role of Vitamin A in haematopoiesis

A 
- RA plays a central role in the
development and differentiation of
leukocytes
- Stem cell differentiation
- Mobilization of iron from storage
sites to the developing red blood cell
for haemoglobin production.
30
Q

Which Vitamin A form may be required for
differentiation of stem cells into red
blood cells?

A

Retinoids

31
Q

Most susceptible population to Vitamin A deficiency

A
  • Preschool children with decreased intake
  • Poor persons
  • Older adults
  • Alcoholism
  • Liver disease
  • Fat malabsorption
32
Q

How does liver disease lead to Vitamin A deficiency?

A

It limits storage

33
Q

Ocular Vitamin A symptoms

A
  • Night blindness
  • Conjunctival xerosis
  • Bitot’s spot
  • Corneal xerosis
  • Keratomalacia
34
Q

Extra-ocular Vitamin A symptoms

A
  • Retarded growth
  • Skin disorders
  • Adverse effects on reproduction
  • Effect on bone
35
Q

Night blindness or inability to see in dim light caused by Vitamin A deficiency is as a result of…

A

…inadequate pigment in the retina

36
Q

Symptoms of eyes with conjunctival xerosis

A

The conjunctiva becomes:

  • dry
  • lustreless
  • non-wettable
  • thickened
  • wrinkled
  • pigmented
37
Q

Bitot’s spots refer to…

A

…built up keratin located superficially in the
conjunctiva. They are raised, silvery white, oval, irregular or triangular patch of keratinized
epithelium.

38
Q

What happens in corneal xerosis?

A

The cornea appears dull with granular pebbly dryness, not wettable and eventually opaque. Severe cases may lead to corneal ulceration, which may heal to
leave scar that affects vision.

39
Q

Keratomalacia refers to…

A
  • Softening and necrosis of the cornea associated with
    vitamin A deficiency
  • Softening, drying and ulceration of the cornea
  • Circular, sharply demarcated steep margins
40
Q

How does Vitamin A deficiency affect the skin?

A

Phrynoderma; dry, keratinized scaly skin.

41
Q

Deficiency symptoms of Vitamin A in the reproductive system

A

Atrophy of germinal epithelium

42
Q

Deficiency symptoms of Vitamin A in the respiratory tract

A

Squamous metaplasia of respiratory

mucosa & ciliary damage

43
Q

Deficiency symptoms of Vitamin A in the gastrointestinal system

A

Reccurent diarrhea

44
Q

Deficiency symptoms of Vitamin A in growth

A

Retardation occurs

45
Q

Therapeutic uses of Vitamin A include…

A
  • Treatment of dry eye
  • Deficiency prophylaxis
  • Use of retinoic acid preparations in treatment of
    psoriasis, acne and several other skin diseases, because of its role in epithelial cell differentiation and integrity
46
Q

Vitamin A toxicity is referred to as…

A

Hypervitaminosis A

47
Q

Acute toxicity symptoms of Hypervitaminosis A

A
  • Headache & dizziness
  • Nausea
  • Vomiting
  • Abdominal pain
  • Pseudotumour cerebri (bulging anterior fontanel)
48
Q

Chronic toxicity symptoms of Hypervitaminosis A

A
  • Anorexia
  • Pruritis
  • Sparse hair
  • Benig n intracranialhypertension
  • Hepatosplenomegaly
49
Q

How does paraffin use affect Vitamin A in the body

A

Regular use of paraffin may cause deficiency because it carries Vitamin A away with it from the body.

50
Q

Which other fat soluble vitamin enhances the storage and functions of Vitamin A?

A

Vitamin E

51
Q

One drug that interferes with Vitamin A absorption?

A

Neomycin. Long term oral neomycin causes steatorrhea and interferes with Vitamin A absorption.

52
Q

How does zinc deficiency affect Vitamin A?

A
  • Reduction of retinol-binding protein synthesis
  • Decreased activity of the enzyme that releases retinol
    from its storage form, retinyl palmitate, in the liver
    -zinc is required by the enzyme that converts retinol into
    retinal
53
Q

What is the enzyme that releases retinol

from its storage form in the liver?

A

Retinyl palmitate

54
Q

Vitamin A deficiency may improve iron deficiency

anaemia. True or false?

A

False. It worsens it.

55
Q

What are the fat-soluble vitamins?

A

A, D, E, K

56
Q

Chemical name for Vit D

A

Cholecalciferol

PHA Vitamins (5 decks)

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