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BB1702 Biochemistry: Structure and Function > Vitamins > Flashcards

Vitamins Flashcards

1
Q

Define vitamin

A

Any of various organic compounds that are needed in the small amounts for notmal growth and activity of the body.

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2
Q

What series of vitamins act as coenzymes?

A

B group vitamins

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3
Q

List the B group vitamins [8]

A
  • Thiamine (B1)
  • Riboflavin (B2)
  • Niacin (nicotinic acid) (B3)
  • Panthothenic acid (B5)
  • Pyridoxine (B6)
  • Cobalamin (B12)
  • Biotin
  • Folic acid
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4
Q

Which vitamins are water-soluble?

A
  • B group vitamins
  • Ascorbic acid (C)
  • Lipoic acid
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5
Q

What do the B group vitamins function as?

A

Coenzymes

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6
Q

What vitamins are lipid-soluble?

A
  • Retinol (A)
  • Tocopherols (E family)
  • Cholecalciferol (D3)
  • Vitamin K
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7
Q

What are the noncoenzyme vitamins?

A
  • Retinol (A)
  • Ascorbic acid (C)
  • Cholecalciferol (D3)
  • Tocopherols (E family)
  • Vitamin K
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8
Q

What is the difference in storage for fat-soluble and water-soluble vitamins?

A

Water-soluble vitamins need to be constantly replenished as they are only stored for the short term. Any excess is secreted in the urine.

Fat-soluble vitamins are stored for the long term in the liver and in fatty tissue so are only needed in small amounts. An excess of this type of vitamin can be toxic as it can easily build up, but not be removed easily.

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9
Q

What are the functions of the derivatives of the vitamin retinol (A)?

A
  • a hormone
  • the visual pigment of the vertebrate eye
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10
Q

Where can retinol (vitamin A) be found?

A
  • yellow and dark green vegetables (beta-carotene)
  • liver
  • eggs
  • whole milk
  • butter
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11
Q

How is retinol (vitamin A) formed?

A

By the cleavage of beta-carotene two produce two retinol molecules

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12
Q

What is retinoic acid derived from and what is its function?

A

Retinoic acid is a derivitive of retinol (vitamin A) and it regulates gene expression in the development of epithelial tissue, including skin.

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13
Q

What is retinal derived from and what is its function?

A

Retinal is derived from retinol. It is the pigment that initiates the response of rod and cone cells of the retina to light, producing a neuronal signal to the brain.

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14
Q

What does 11-cis-retinal become when it associates with an opsin?

A

The visual pigment found in rod cells, rhodopsin

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15
Q

What happens to11-cis-retinal when it reacts with light?

A

It becomes all-trans-retinal

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16
Q

What does a retinol (vitamin A) deficiency cause?

A
  • Dryness of skin, eyes, and mucous membranes
  • retarded development and growth
  • night blindness
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17
Q

Where and how is cholecalciferol (vitamin D3) formed?

A

Cholecalciferol is normally formed in the skin from 7-dehydrocholesterol in a photochemical reaction driven by the UV component of sunlight.

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18
Q

Vitamin D3 (cholecalciferol) is not itself biologically active, but it is converted by _______ in the _____ and ______ to 1,25-_________cholecalciferol, a hormone that regulates _______ uptake in the intestine and _______ levels in the kidney and bone.

A

Vitamin D3 (cholecalciferol) is not itself biologically active, but it is converted by enzymes in the liver and kidney to 1,25-dihydroxycholecalciferol, a hormone that regulates calcuim uptake in the intestine and calcuim levels in the kidney and bone.

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19
Q

What does a cholecalciferol (vitamin D3) deficiency lead to?

A
  • Defective bone formation
  • Rickets
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20
Q

Where can cholecalciferol (vitamin D3) be found?

A
  • saltwater fish (salmon, sardines, herring)
  • liver
  • egg yolk
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21
Q

What are the steps [2] to get from 7-dehydrocholesterol to cholecalciferol (vitamin D3)?

A
  1. UV light causes an electron rearrangement in the second carbon ring
  2. isomerisation and electron rearrangement
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22
Q

What is another name for 1,25-dihydroxycholecalciferol?

A

Calcitriol

23
Q

What do tocopherols (vitamin E) do?

A

Act as a biological antioxidant

24
Q

How does the structure of tocopherols (vitamin E) help it carry out its function?

A

The aromatic ring reacts with and destroys the most reactive forms of oxygen radicals and other free radicals.

This protects unsaturated fatty acids from oxidation and preventing oxidative damage to membrane lipids, which can cause cell fragility.

25
Q

Where can tocopherols (vitamin E) be found?

A
  • eggs
  • vegetable oils
  • wheat germ
26
Q

What does a tocopherol (vitamin E) deficiency cause?

A

A tocopherol deficiency is very rare in humans, but the principal symptom is fragile erythrocytes.

27
Q

What is the function of vitamin K?

A

It plays an important role in blood cloting by undergoing a cycle of reduction and oxidation during the formation of prothrombin.

28
Q

What does a vitamin K deficiency cause?

A

It is very rare to have a vitamin K deficiency, but it would cause slowed blood clotting.

29
Q

Where can vitamin K be found?

A
  • Vitamin K1 (phylloquinone) is found in green plants and leaves
  • Vitamin K2 (menaquinone) is formed by bacteria living in the vertebrate intestine
30
Q

How does vitamin K help the synthesis of clotting factors?

A

It is required for the γ-carboxylation of glutamic acid in several clotting factors

31
Q

What does warfarin mimic and what is its function?

A

Warfarin mimics vitamin K and therefore inhibits blood clotting by inhibiting the formation of active prothrombin.

32
Q

What is dicoumarol?

A

A drug for treating people at risk of excessive blood clotting (coronary thrombosis)

33
Q

What is the coenzyme derivative of thiamine (B1) and what is its function?

A
  • thiamine pyrophosphate (TPP)
  • aldehyde transfer
34
Q

What does a thiamine (B1) deficiency cause?

A

Beriberi - weight loss, heart problems, neurological dysfuntion

35
Q

Where can thiamine (B1) be found?

A
  • grains
  • seeds
  • meat
36
Q

What is the coenzyme derivative of riboflavin (B2) and what is its function?

A
  • Flavin adenine dinucleotide (FAD)
  • oxidation-reduction reactions
37
Q

Where can riboflavin (B2) be found?

A
  • milk
  • leafy vegetables
  • fresh meat
  • egg yolk
38
Q

What is the coenzyme derivative of niacin (B3) and what is its function?

A
  • NAD/NADP
  • oxidation-reduction reactions
39
Q

Where can niacin (B3) be found?

A
  • meat
  • yeast
40
Q

What does a niacin (B3) deficiency cause?

A

Pellagra - dermatitis, depression, and diarrhoea

41
Q

What is the coenzyme derivative of pantothenic acid (B5) and what is its function?

A
  • Coenzyme A (CoA)
  • acyl-group transfer reactions
42
Q

What does a pantothenic (B5) deficiency cause?

A

Hypertension

43
Q

What is the coenzyme derivative of pyridoxine (B6) and what is its function?

A
  • Pyridoxal phosphate (PLP)
  • group transfer to or from amino acids
44
Q

Where is pyridoxine (B6) found?

A
  • meat
  • vegetables
  • whole-grain cereals
45
Q

What does a pyridoxine (B6) deficiency cause?

A

Depression, confusion, convulsions

46
Q

Where can biotin be found?

A
  • peanuts
  • chocolate
  • eggs
47
Q

What is the coenzyme derivative of biotin and what is its function?

A
  • biotin-lysine adducts (biocytin)
  • carboxyl-group transfers
48
Q

What is the coenzyme derivative of folic acid and what is its function?

A
  • Tetrahydrofolate
  • transfer of one-carbon components; thymine synthesis
49
Q

Where can folic acid be found?

A
  • green vegetables
  • fresh fruit
  • liver
50
Q

What does a folic acid deficiency cause?

A

Anaemia in adults, neural tube defects in foetuses

51
Q

What is the function of ascorbic acid (vitamin C)?

A

Ascorbic acid acts as an antioxidant and is required for the hydroxylation of collagen.

The hydroxylation of collagen (proline) is essential for triple helix formation.

52
Q

Where can ascorbic acid (vitamin C) be found?

A
  • citrus fruits
  • peppers
53
Q

Where does an ascorbic acid (vitamin C) deficiency cause?

A

Scurvy - skin lesions, fragile blood vessels, loose teeth, swollen and bleeding gums

BB1702 Biochemistry: Structure and Function (12 decks)

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