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Nutrition and Metabolism > Vitamins > Flashcards

Vitamins Flashcards

1
Q

Define a vitamin.

A

Complex organic substance required in the diet. Absense/insufficient amount causes deficiency.

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2
Q

Which vitamins are fat soluble?

A

Vitamin A, D, E and K

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3
Q

Which vitamins are water soluble?

A

B group and vitamin C

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4
Q

Which type of vitamins are stored in the body easily? Fat/water soluble?

A

Fat soluble

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5
Q

Which type of vitamins are usually toxic in excess? Fat/water soluble?

A

Fat soluble

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6
Q

What is the main significance of B-group vitamins?

A

All B vitamins act as co-enzymes in metabolic pathways.

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7
Q

What are sources of Thiamin (vitamin B1)?

A 
Whole grain
Pork
Fish
Vegetables
Dairy
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8
Q

What foods are deficient in thiamin (B1)?

A

Polished rice, sugar, fat, refined/processed foods

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9
Q

What is the daily reference value for thiamin?

A
  1. 4mg/day male

1. 0mg/day female

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10
Q

How does a high carbohydrate diet effect B1 requirement?

A

Increases the requirement for B1 (thiamin)

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11
Q

What is the biochemical role of vitamin B1 (thiamin)?

A

As thiamin pyrophosphate co-enzyme in conversion of pyruvate > acetyl CoA
Deficiency results in accumulation of lactate in muscles.

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12
Q

Name the two conditions associated with thiamin deficiency.

A

Beri-beri

Wernicke-Korsakoff syndrome

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13
Q

What are the different types of beri-beri and how do they present?

A
  1. Infantile beri-beri = sudden onset, cardiovascular symptoms
  2. Acute cardiac beri-beri (Wet Beri-beri) - heart failure, enlarged heart and liver. Can result from excess chronic alcohol intake.
  3. Chronic dry beri-beri - symettrical ascending peripheral neuropathy. Weakness, numbness, ataxic gait, paingul extremeties.
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14
Q

What is Wernicke-Korsakoff’s syndrome?

A

Also known as cerebral beri-beri.
Mainly seen in alcoholics due to B1 deficiency.
Alcohol inhibits active transport of thiamin from intestine and inhibits the enzyme which converts thiamin to TPP.
Confusion, ataxia, disorientation in space and time.
Progresses to Korsakoff’s Psychosis if untreated.

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15
Q

Why do alcoholics tend to suffer from many B vitamin deficiencies?

A

Alcoholics tend to have adequate energy intake but as empty calories.
GI tract malfunctions are commons.
Cirrhotic liver - affects storage, transport and metabolism of many vitamins.

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16
Q

What vitamin is Riboflavin?

A

Vitamin B2

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17
Q

What are sources of riboflavin (B2)?

A

Mainly found in milk - associated with protein.

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18
Q

What is the function of B2 in the body?

A

As FAD and FMN in redox reactions.

- Oxidising agents.

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19
Q

What is riboflavin (B2) deficiency?

A

Very rare - except in alcoholics.

Mild symptoms: Cheilosis, cataracts, anglular stomatistis.

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20
Q

What vitamin is Niacin?

A

B3

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21
Q

Name two vitamers of niacin.

A

Nicotinic acid

Nicotinamide

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22
Q

What is the function of niacin (B3) in the body?

A

As NAD and NADP in redox reaction.

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23
Q

What are sources of niacin (B3)?

A

In cereals in small amounts.

Mainly synthesised by the body from tryptophan.

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24
Q

What deficiency is caused by insufficient Niacin intake? (B3 deficiency)

A

Pellagra

4 Ds: Diarrhoea, Dermatitis, Dementia, Death

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25
Q

Name 2 vitamers of pyridoxine (vitamin B6).

A

Pyridoxamine

Pryridoxal

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26
Q

What is the function of Pyridoxine (B6) in the body?

A

Active form = pyridoxal phosphate

Essential for amino acid metabolis, and haem synthesis.

27
Q

What are sources of pyridoxine?

A

Fish, beef, vegetables, potatoes, yams, eggs, non-citrus fruits

28
Q

How is B6 deficiency presented?

A

Secondary deficiency - caused by antagonists: ionazid (TB treatment) combines with pyridoxal phosphate and disables it.

29
Q

Is pyridoxine toxic in excess?

A

Yes - severe peripheral neuropathy.
Hyperaesthia, paraesthesia, muscle weakness, numbness.
Occurs in women self medicating for PMS (500-5000mg/day)

30
Q

What is the function of vitamin B12 in the body?

A

Carrier of methyl groups in metabolism.

31
Q

What is the function of Folate (B9) in the body?

A

Carrier of 1-carbon units.

Its active form is tetrahydrofolate - this is maintained by dihydrofolate reductase.

32
Q

How is B12 absorbed?

A

Only found in animal tissues.
Bind to intrinsic factor secreted by gastric cells.
Lack of intrinsic factor is the commonest cause of B12 deficiency.

33
Q

What are sources of folate?

A

Mainly found in green vegetables, liver and whole grains.

34
Q

What are the metabolic functions of folate and B12? How do they connect?

A

Folate - 1-C transfer reaction in purine and pyrimidine synthesis and amino acid metabolism.
B12 - conversion of homocysteine to methionine and methylation of myelin.
B12 takes methyl group from MeTHF and regenerates THF hence B12 is required for folate use.

35
Q

What is caused by a deficiency of B12 or Folate?

A

Deficiency of either will cause elevated levels of homocysteine.
Leads to megaloblastotic anaemia - many large nucleated, immature red blood cells.
Can also result in inadequate myelin synthesis - neural problems.

36
Q

What are causes of B12 and Folate deficiencies?

A 
B12:
 - absent/defective intrinsic factor
 - gastric atrophy
 - coeliac disease
 - crohn's disease
Folate:
 - malabsorption
 - tropical sprue
 - drugs (barbituates and anti-convuslants)
37
Q

What vitamin is pantothenic acid?

A

Vitamin B5

38
Q

What is the function of pantothenic acid (B5)?

A

Component of Co-enzyme A in metabolism and transfer of carbon chains.

39
Q

What vitamin is biotin?

A

Vitamin B7

40
Q

What are sources of biotin (B7)?

A

Peanuts, chocolate, egg yolk.

Sufficient amounts are synthesised by intestinal bacteria.

41
Q

What is the function of biotin (B7)

A

Prosthetic group for carboxylation.
pyruvate > oxaloacetate
acetyl CoA > malonyl CoA

42
Q

How can B7 deficiency be cause?

A

Long term antibiotic therapy - kills intestinal bacteria so not enough biotin can be synthesised.

43
Q

Where is vitamin C found?

A

Citrus fruits, tomatoes, berries

44
Q

What is the function of vitamin C in the body?

A

Anti-oxidation nutrient.
Enables hydroxylation of proline and lysine in collagen formation as it maintains Fe2+ oxidation state for hydralase activity to function.

45
Q

What is vitamin C deficiency?

A

Scurvy - wounds don’t heal, haemorrhages, anaemia

46
Q

How much vitamin C does the body store?

A

6 month store.

Signs of scurvy start to show after 3 months without vitamin C.

47
Q

How does smoking affect vitamin C requirement?

A

Smokers require twice the normal intake of vitamin C.

48
Q

What are the risks of megadoses of vitamin C?

A

Oxalate kidney stones
Diarrhoea
Systematic conditioning - babies born with higher requirements.

49
Q

What are sources of vitamin A?

A 
As retinol - animla liver, fish liver oil, whole milk, egg yolk
Plant carotenoids (beta-carotene)
50
Q

How are carotenoids absorbed? (vitamin A)

A

Carotenoids are cleave to 2 retinol molecules but conversion is inefficient.
6 carotenoids produce 1 molecule of retinol.

51
Q

What are the functions of vitamin A in the body?

A

Retinoic acid - controls protein synthesis. Binds to receptors in cytosol and binds to chromatin affecting synthesis of proteins involved in cell growth and differentiation.

52
Q

How is vitamin A transported and stored?

A

Transported in chylomicrons.

Transport from liver to tissues bounds to retinol binding proteins and pre-albumin.

53
Q

What is vitamin A deficiency?

A

Very rarely seen in developed countries.

Night blindness, progressive keritinisation of the cornea (xerophthalamia) - ketomalacia and irrevesible blindness.

54
Q

Is excess vitamin A toxic?

A

Yes - causes dermatitis, hair loss, hepatic disfunction, thinning/fraction of long bones.

55
Q

What are sources of vitamin E?

A

Vegetable oils (wheat germ oil, nuts and green veg)

56
Q

What is the safe level of vitamin E?

A

up to 1g/day

57
Q

What is the function of vitamin E ?

A

Prevents oxidation of unsaturated fatty acids - normally susceptible to attack by free radicals - would disrupt cell membrane etc.
Instead vitamin E becomes radical but is stable.

58
Q

What is vitamin E deficiency?

A

Only known in premature babies as:
- vitamin E does not easily cross the placenta.
- human milk s not a good source of vitamin E.
Causes haemolytic anaemia due to fragility of red blood cells membranes.

59
Q

What are the two type of vitamin D and where are they found?

A

D3(cholecalciferol) - occurs in animals. Acts as a steroid hormone and interacts with DNA. Can be made by UV stimualtion.
D2 (ergocalciferol) - derived from ergosterol from fungi and plants. Used as a foof additive.

60
Q

What is the function of vitamin D?

A

Maintains correct level of calcium and phosphate in the blood.

61
Q

What is vitamin D deficiency? Children and adults

A

Rickets in children:
- mineral:matrix ratio decreases in bones
- bending of long bones and hyphosis.
Osteomalacia in adults:
- muscle weakness, bone pain, decalcification of long bones.
- borderline case in elderly in UK

62
Q

Is vitamin D toxic in excess?

A

Yes.
Hypercalcaemia, GI tract disturbances, calcification of soft tissues.
Can be fatal if severe.
10x normal intake = toxic

63
Q

What are sources of vitamin K?

A

Green leafy vegetables, small amounts in milk, eggs and cereals.
Considerable amount synthesised by intestinal bacteria.

64
Q

What is vitamin K deficiency? Seriousness?

A

VERY SERIOUS
- Defective blood clotting as it depends on protein cascade which is interfered in vitamin K deficiency.
- Can occur in long term antibiotic therapy.
Haemorrhagic disease of the new born - can develop intracranial haemorrhages. Either die or a born with severe neurological malfunctions.

Nutrition and Metabolism (11 decks)

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