fat soluble vitamins

Question 1

what are the 4 fat soluble vitamins

Answer 1

ADEK

Question 2

what are vitamins?

Answer 2

organic compounds with great variability as they can no chemical resemblance to each other,

Question 3

characteristics of a fat soluble vitamins

Answer 3

1.absorped as a dietary lipid
2.stored in lipid part of body and liver
3.not readily excreted

Question 4

the steps of absorption

Answer 4

there is anlipid emission that breaks them into bile salt micelles which enters an intestinal mucosal cell exiting as chomolycron

Question 5

vit A explain

Answer 5

Generic term to describe a group of compounds that exhibit the biological activity of retinol
ACTIVITY:
retinol and related compounds
some caritinoids

Question 6

what is retinol

Answer 6

the precursor of biologically active retinoids
CH2OH
a major transport form of vit A
produced by enterocytes

Question 7

retinyl ester

Answer 7

storage form of vit a

Question 8

retinalaldehyde

Answer 8

intermediate for the conversion of retinol to retenoic acid

Question 9

retinoid acid

Answer 9

the active form in all tissues except the retina

Question 10

percentages of absorption of retinol

Answer 10

90% is absorbed
50% stored primarily in the liver
20% in faeces less polar retinoids
17% in urine charged acidic retinoids
3% releases as co2

Question 11

what are carotenoids

Answer 11

Fat-soluble pigments synthesised by plants
➢ 2 categories
* Pro-vitamin A carotenoids
* Non pro-vitamin A
➢ Structure – highly unsaturated
➢ Carotenoid most efficiently processed to
Retinol is all-trans-b-carotene
➢ Carotenoid absorption – passive diffusion, requires dietary fat

Question 12

what are the roles of retinoid binding proteins

Answer 12

.
1.Transport retinol through the aqueous extra/intracellular environment

2.Protect retinol from unwanted processing and damage
3.Deliver retinol to appropriate enzymes

4.Limit the level of free retinol in membrane

Question 13

explain the transport and metabolism of retinoids

Answer 13

involves a series of hydrolysis and esterification reactions
dietary pre formed retinol esters are hydrolysed in the I testing lumen to produce free retinol
most vit a is in liver

Question 14

vit a functions

Answer 14

➢Vision: Production of Rhodopsin
➢ Growth, Reproduction, Lactation
➢Cell differentiation
➢ Embryogenesis
➢Immune response
➢ Maintenance of epithelial cells
➢ Bone & Tooth growth
➢Antioxidant role
➢ Retinoids: well established chemotherapeutic agents

Question 15

explain vit A in regards to vision

Answer 15

The retina transforms light energy into nerve impulses using special pigment molecules in the retinal cells, cones & rods
➢ Each retinal cell contains ~30million molecules of a retinaldehyde containing visual pigment called rhodopsin
➢ Rhodopsin consists of: ➢A protein called opsin
➢A molecule of 11-cis retinaldehyde covalently bound

Question 16

deficiency ans toxic of vit a

Answer 16

Xerophthalmia (night blindness) ➢ Hyperkeratosis
➢Poor growth
➢ Reduced immunocompetence
Deficiency
➢ Acute toxicity (>200mg adults) – vomiting, abdominal pain, headaches, anorexia, blurred vision
➢ Chronic toxicity (10mg consumed over periods of month) – headache, ataxia, alopecia, skin disorders, liver toxicity, hyperlipidaemia, muscle/bone pain

Question 17

explain Vit D

Answer 17

Generic term used to describe antirachtic compounds derived from sterols
➢ Ergocalciferol (D2)
➢ Cholecalciferol (D3)
➢Formed by UV irradiation of their provitamins (ergosterol
& 7-dehydrocholesterol)
➢ Dietary source – liver, fatty fish, egg yolks, fortified milk
➢The hormonally active form of vitamin D is not widely distributed in nature
normal dietary form calciol and chaliciferol
active form calcitrol

Question 18

what are the biological actions of vit d

Answer 18

Regulation of Calcium & bone homeostasis ➢Blood glucose regulation - 1,25(OH)2D3 may play a
role in insulin secretion
➢ Immunomodulation – may enhance innate immunity
➢Cell growth & differentiation - 1,25(OH)2D3 inhibits proliferation & stimulates differentiation (Uncontrolled proliferation??)
➢ Blood pressure regulation

Question 19

explain vit D in regards to metabolism

Answer 19

vit Must be metabolised in its active form, sites of transformation include liver and kidney,