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BB1702 Biochemistry: Structure and Function > Vitamins > Flashcards

Flashcards in Vitamins Deck (53)
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Define vitamin

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


What series of vitamins act as coenzymes?

B group vitamins


List the B group vitamins [8]

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


Which vitamins are water-soluble?

  • B group vitamins
  • Ascorbic acid (C)
  • Lipoic acid


What do the B group vitamins function as?



What vitamins are lipid-soluble?

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


What are the noncoenzyme vitamins?

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


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

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.


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

  • a hormone
  • the visual pigment of the vertebrate eye


Where can retinol (vitamin A) be found?

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


How is retinol (vitamin A) formed?

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


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

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


What is retinal derived from and what is its function?

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.


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

The visual pigment found in rod cells, rhodopsin


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

It becomes all-trans-retinal


What does a retinol (vitamin A) deficiency cause?

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


Where and how is cholecalciferol (vitamin D3) formed?

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


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.

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.


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

  • Defective bone formation
  • Rickets


Where can cholecalciferol (vitamin D3) be found?

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


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

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


What is another name for 1,25-dihydroxycholecalciferol?



What do tocopherols (vitamin E) do?

Act as a biological antioxidant


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

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.


Where can tocopherols (vitamin E) be found?

  • eggs
  • vegetable oils
  • wheat germ


What does a tocopherol (vitamin E) deficiency cause?

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


What is the function of vitamin K?

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


What does a vitamin K deficiency cause?

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


Where can vitamin K be found?

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


How does vitamin K help the synthesis of clotting factors?

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