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Physiology 3003 > Lecture 11--Metabolism of vitamins > Flashcards

Lecture 11--Metabolism of vitamins Flashcards

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1
Q

What are the lipid soluble vitamins

A

Vitamin A, D, E, K

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2
Q

How are the lipid soluble vitamins ABSORBED?

A

…by DIFFUSING through plasma membranes

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3
Q

How are the lipid soluble vitamins TRANSPORTED?

A

…in LIPOPROTEINS or complexed to SPECIFIC BINDING PROTEINS

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4
Q

How are lipid soluble vitamins stored?

A

Readily stored… predominantly stored in the liver

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5
Q

What are the water soluble vitamins?

A

B Vitamins

Vitamin C

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6
Q

How are the water soluble vitamins ABSORBED?

A

through specific CHANNELS

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7
Q

How are water soluble vitamins TRANSPORTED?

A

Dissolved in blood

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8
Q

What’s special about Vitamin B12?

A

Vitamin B12 does not have a specific channel/carrier protein on the surface of cells.
Needs to be actively transported COMPLEXED TO INTRINSIC FACTOR

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9
Q

How are water soluble vitamins stored?

A

Because they are HYDROPHILIC they are not readily stored .: a DAILY SUPPLY IS REQUIRED (in diet)

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10
Q

What are/is the precursor(s) for Vitamin A?

A

(1) PLANT form: B-CAROTENE

(2) ANIMAL form: RETINOL ESTER

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11
Q

What enzyme deficiency can lead to a vitamin A deficiency? This is specifically an issue for which group in the population?

A

A deficiency in the ENZYME that CONVERTS B-CAROTENE –> RETINOL can lead to a vitamin deficiency

Especially in VEGETARIANS (who aren’t getting Retinol ester (precursor for it A) in their diet.

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12
Q

Outline the processing of B-Carotene and retinol esters…

Gut:
Enterocyte:
Export into blood:

A

–B-CAROTENE:
Gut: B-carotene
Enterocyte: B-carotene–>retinAL –>RetinOL–>Retinol Ester –> CHYLOMICRON

–RETINOL ESTER:
Gut: Retinol ester –> Retinol
Enterocyte: Retinol –> Retinol Ester –> CHYLOMICRON

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13
Q

What are the modifications of vitamin A that occur in the liver? What function do they serve?

A

For EXPORT: Retinol ester==> RETINOL

For STORAGE: RETINOL ESTER

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14
Q

What is the STORAGE FORM of vitamin A? Where is it stored?

A

Retinol Ester

The liver

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15
Q

What is the ACTIVE FORM of vitamin A?

A

RETINOIC ACID

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16
Q

How is vitamin A transported in the blood?

A

Bound to RETINOL BINDING PROTEIN (RBP)

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17
Q

What is the MAIN ROLE of Vitamin A?

A

VISUAL PIGMENT

1) Retinol–converted–> Retinoic Acid (Active form) (in the retina
(2) Retinoid Acid + Opsin –> RHODOPSIN

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18
Q

What is RHODOPSIN? From what is Rhodopsin synthesised?

A

RHODOPSIN = the visual pigment. Used for PHOTO-TRANSDUCTION in the retina. Converts light –> biochemical messages enabling us to perceive light…

Opsin + Retinoid Acid (Active form of it A) = RHODOPSIN

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19
Q

What are the 3 general uses for Vitamin A?

A

(1) VISUAL PIGMENT (Retinoid acid + Opsin = Rhodopsin)
(2) TRANSCRIPTION COFACTOR (essential in embryonic development, excess/deficiency = TERATOGENIC)
(3) Form is used as a CHEMOTHERAPEUTIC (kills highly proliferative cells, causes cells to differentiate, big side effects)

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20
Q

What are the symptoms of a deficiency in vitamin A?

A

(1) Night blindness

(2) Follicular hyperkeratosis

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21
Q

What symptoms are there for toxicity of vitamin A?

A

(1) Vomiting
(2) Headache
(3) Impaired vision
(4) Weight loss
(5) Excessive bone growth (stimulates osteoblast metabolism)

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22
Q

What is the active form of Vitamin D?

A

CALICTRIOL (1,2,5-dihydroxy D3)

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23
Q

How is vitamin D transported in the blood?

A

Bound to VITAMIN D BINDING PROTEIN (VDBP)

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24
Q

Outline the processing/transport of vitamin D

A

SKIN: Cholesterol –> CHOLECALCIFEROL (vit D3)

LIVER: Cholecaliferol –> 2, 5 hydroxy D3

KIDNEY: 2, 5 hydroxy D3 –> CALITRIOL (1, 2, 5 dihydroxy-D3)

BLOOD: Calcitriol is bound to vitamin D binding protein (VDBP)

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25
What is the function of vitamin D?
Primarily by role in Ca2+ METABOLISM --maintain Ca2+ Balance - -> ++ Ca2+ absorption (small intestine) - -> ++ Ca2+ reabsorption (kidney) - -> ++ bone mineralisation
26
What is the effect of vitamin D on Ca2+ metabolism in the body?
- -> ++ Ca2+ absorption (small intestine) - -> ++ Ca2+ reabsorption (kidney) - -> ++ bone mineralisation
27
Deficiency in vitamin D
= problems with bone metabolism | => RICKETS (soft pliable bones, impaired ossification of osteoid)
28
How is Ca2+ absorbed?
TRANSCELLULAR ROUTE
29
What is the function of CALBINDIN?
>Found In the cytosol >Binds to Ca2+ >LOWERS THE ACTIVE CONCENTRATION OF Ca2+ within the cell .: maintaining the [gradient] required for passive diffusion >Also stops it from being biologically active
30
How does vitamin D regulate Ca2+ absorption?
Transcellular absorption of Ca2+ is vitamin D DEPENDENT... | ....Vitamin D activates the transcription of CAT 1 and Calbindin
31
In which family of vitamins does vitamin E belong? Which is the most biologically active form in this family?
TOCHOPHEROLS 4 members: alpha (a), beta (b), gamma (y), delta (d) a-TOCHOPHEROLS = most biologically active form
32
How is vitamin E transported from the; (1) GUT --> LIVER? (2) LIVER-->TARGET ORGANS?
(1) In CHYLOMICRONS | 2) bound to a-TOCHOPHEROL TRANSPORTER PROTEIN (a-TTP
33
What are the 2 main functions of vitamin E?
(1) ANTIOXIDANT (prevents free radical damage to PLASMA MEMBRANES by picking FRs and being Oxidised==can be RECHARGED by vitamin V and converted from OXIDISED form --> REDUCED form) (2) COFACTOR (synthesis of unsaturated FAs in mitochondria)
34
What is the result of vitamin E deficiencies?
(1) reduced fertility (in men) (2) Peripheral neuropathy (3) Anaemia
35
What mutation/metabolic issue might lead to a vitamin E deficiency?
(1) a-TPP MUTATION | 2) Fat absorption problem (Vit E= lipid soluble vitamin
36
Toxicity in vitamin E
RARE | causes ++ bleeding
37
Compare and contrast lipid and water soluble antioxidants
Vitamin E = lipid soluble antioxidant Vitamin C = Water soluble antioxidant They differ in that ... >Vitamin C typically prevents free radical damage (FRD) in the CYTOSOL of cells WHEREAS >Vitamin E typically prevents FRD to the outside of cells (plasma membranes, FFA etc.) These differences are due to their different solubilities
38
What is/are the precursor(s) for vitamin K?
1) PLANT form: K1 (PHYLLOQUINON) | 2) Animal form: K2 (MENAQUINON)
39
What is the FUNCTION of vitamin K
(1) Dominant role as COFACTOR IN BLOOD CLOTTING REACTIONS (='koagulations vitamin') (2) Bone metabolism (3) Cell growth (4) Bone mineralisation
40
Vitamin K plays a 'secondary role' in blood clotting reactions/bone metabolism. What does this mean?
Vitamin K is an important cofactor in BCR & bone metabolism because it CONVERTS PROTEINS involved in these processions from INACTIVE --> ACTIVE forms through POST-TRANSLATIONAL MODIFICATION.
41
What post-translational modifications to proteins are initiated by vitamin K?
Converting proteins involved in blood clotting reactions/bone metabolism from inactive-->active forms by CARBOXYLATION OF GLUTAMATE RESIDUES ON THE GLA DOMAINS OF PROTEINS
42
What is the toxicity to vitamin K?
No known toxicity
43
How is vitamin K used in a clinical setting?
Clinical application in newborns Babies are not good fat absorbers .: often vitamin K deficient (initially) which means they are prone to excessive bleeding if they 'spring a leak' .: injecting newborns with vitamin K promotes blood clotting when/if neccessary
44
What are the consequences of a DEFICIENCY in vitamin K?
(1) Blood clotting disorders | 2) Can lead to OSTEOPOROSIS (due to role in bone metabolism
45
What could cause a vitamin K deficiency?
RARE | Liver failure --> absence of bile secretion --> not absorbing fats
46
What are the general functions of the B vitamins?
(1) COFACTORS IN METABOLIC PROCESSES (protein, CHO & fat metabolism) .: essential in producing energy (2) COENZYMES are derived from Vitamin B
47
Name: Vitamin B1
B1= THIAMINE
48
Name: Vitamin B2
B2= RIBOFLAVIN
49
Name: Vitamin B3
B3= NIACIN
50
Name: Vitamin B5
B5= PANTOTHENIC ACID
51
Name: Vitamin B6
B6= PYRIDOXINE & PYRIDOXAMINE
52
Name: Vitamin B7
B7= BIOTIN
53
Name: Vitamin B9
B9= FOLIC ACID
54
Name: Vitamin B12
B12= COBALAMIN
55
Recite all the water soluble vitamins (with proper names) to the tune of twinkle twinkle
``` 1 is thiamine Riboflavin's 2 3 is niacin ...Hey B4 where are you? 5 is pantothenate Pyridoxine's 6 7 is biotin and 12's cobalamin Those are the B's then comes C and FOLATE (B9) ANDDD THOSE WERE ALL THE WATER SOLUBLE VITAMINS I ATE ```
56
What is the active coenzyme of B1
TPP (Thiamin pyrophosphate)
57
What is the active coenzyme of B2
FAD/FADH
58
What is the active coenzyme of B3
NADH/NADH & NADP
59
What is the active coenzyme of B5
Acetyl CoA
60
What is the active coenzyme of B6
PLP
61
What is the active coenzyme of B7
Biotin
62
What is the active coenzyme of B9
THF
63
What is the active coenzyme of B12
B12 (cobalamin)
64
What causes BERI-BERI? Symptoms?
Beri Beri is caused by severe THIAMINE (B1) deficiency - -severe muscle weakness - -Muscle wasting - -Delerium & memory loss
65
What causes Pellagra? Symptoms? Who is at an increased risk?
Severe NIACIN (B3) deficiency x4 D's: (1) Diarrhoea (2) Dermatitis (loss of rapidly proliferating cells) (3) Dementia (Neuronal activity requires a lot of energy) (4) Death Increased risk in (1) longterm ALCOHOLICS (due to reduced vitamin absorption, esp niacin) (2) POOR DIET (e.g. corn based diets are low in tryptophan)
66
B3 (niacin) is synthesised from _______ in the ______. | It's rate of synthesis is ____ and requires vitamin _______.
from TRYPTOPHAN (essential AA) in the LIVER rate of synthesis is SLOW requires vitamin B6 (pyridoxine)
67
Which vitamin is involved in nucleotide/nucleic acid synthesis?
``` Vitamin B9 (Folate) The backbone of folate is used to synthesise purines & pyrimidines (essential for NT/NA synthesis) ```
68
What is the biologically active form of vitamin C?
L-enantiomer = biologically active form
69
What are the functions of vitamin C?
(1) ANTIOXIDANT (preventing FRD in cytosol) (2) COFACTOR in some metabolic processes (synthesis of adrenaline/dopamine) (3) COLLAGEN SYNTHESIS (effects of vit C deficiency = symptomatic scurvy due to this function)
70
What function of vitamin C leads to symptomatic scurvy in Vit. C deficiency?
The role of vit. C in COLLAGEN SYNTHESIS
71
What lifestyle factors can increase risk for developing a vitamin B7 (biotin) deficiency?
eating a lot of raw egg whites over long period drags out B7!
72
What are the results of a moderate vitamin C deficiency?
1. fatigue 2. personality change 3. decline in psychomotor performance & motivation
73
What are the results of severe vitamin C deficiency?
SYMPTOMATIC SCURVY - spongy gums - liver spots on skin - bleeding from mucous membranes
74
What are the two states in which vitamin C exists? Why does it exist in multiple states?
(1) ASCORBATE (vit C) (reduced) (2) DEHYDROASCORBATE (oxidised form vit C) Exists in two states due to it's role as an antioxidant

Physiology 3003 (15 decks)

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