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Biochemistry MBBS > Vitamins > Flashcards

Vitamins Flashcards

1
Q

Vitamin present only in animal diet

A

B12

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2
Q

Marker of vitamin B2 def

A

Glutathione reductase activity

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3
Q

Vitamin syn by bacteria

A

B2,B5 , B7 ,K

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4
Q

Functions of PLP

A
  1. Transamination
  2. Decarboxylations
  3. Heme metabolism
  4. Sulphur metabolism(2 steps)
  5. Glycogenolysis ( phosphorylase)
  6. Niacin synthesis( kynureninase)
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5
Q

Vitamin B6 marker

A

Transaminase
Simple decarboxylation
Protein metabolism
Glycogen phosphorylase

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6
Q

Deficiency manifestations of B6 deficiency

A
  1. Reversible peripheral neuritis ( decarboxylation )
  2. Pellagra ( niacin deficiency)
  3. Hypochromic microcytic anaemia
  4. Homocystinuria
  5. Xanthurenic aciduria
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7
Q

B6 RDA

A

Adults 1 - 2 mg/day

Pregnancy and lactation 2.5

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8
Q

Two atypical vitamin

A

Niacin B3 and D3

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9
Q

Why is zinc important for retinol metabolism

A

Zinc is a part of alcohol dehydrogenase to convert retinal to retinol

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10
Q

Other functions of vitamin A (carotenoids)

A
  1. Like a hormone in tissue differentiation
  2. Reproduction ( retinol )
  3. Antioxidant
  4. Skin health ( against psoriasis)
  5. Against heart diseases
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11
Q

Deficiency manifestations of vitamin A

A
  1. Bitots spots in conjunctiva
  2. Keratomalacia (corneal ulcer)
  3. Preventable blindness
  4. Skin and mucous membrane lesions
  5. Night blindness and xerophthalmia

Most common vitamin deficiency

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12
Q

Daily dosage of vitamin A

A

Children 400- 600 microgram/day
Women 750
Men 750 - 1000
Pregnancy 1000

Richest sources are halibut liver oil, fish oil

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13
Q

Vitamin D requirement

A

Children 10 microgram/day or 400 IU
Adults 5 - 10
Pregnancy, lactation 10
Old age 15

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14
Q

Functions of vitamin E

A
  1. Antioxidant
  2. Against hemolysis
  3. Anti aging
  4. Against atherosclerosis
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15
Q

Vitamin E and selenium

A

Glutathione peroxidase and Vitamin E are synergistic in preventing lipid peroxidation.

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16
Q

RDA of vitamin E

A

Males 10mg/day
Females 8
Pregnancy 10
Lactation 12

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17
Q

Clotting factors activated by vitamin K

A 
2 prothrombin 
7 SPCA
9 Christmas factor
10 Stuart prower factor 
Via gamma carboxylation of glutamic acid residues
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18
Q

RDA of vitamin K

A

50 - 100 mg/day

Deficiency rare , except in preterm babies

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19
Q

Earliest manifestation of vitamin B1 or thiamine

RDA of thiamine

A

Decreased Erythrocyte transketolase activity

1 - 1.5 mg/day (depends on calorie intake)

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20
Q

Functions of FMN

A
  1. Amino acid oxidation O2 to H2O2

2. In respiratory chain in between NAD+ & CoQ

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21
Q

FAD dependent enzymes

A
  1. Succinate to fumarate by succinate dehydrogenase
  2. Acyl Co-A dehydrogenase on acyl Co-A
  3. Xanthine to uric acid by xanthine oxidase
  4. Pyruvate dehydrogenase & alpha keto glutarate dehydrogenase
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22
Q

NADPH generating reactions

A
  1. G-6-PD in HMP
  2. 6-Phosphogluconate dehydrogenase in HMP
  3. Cytoplasmic isocitrate dehydrogenase
  4. Malic enzyme
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23
Q

NADPH utilising reactions

A
  1. Beta keto acyl ACP dehydrogenase
  2. Alpha, BetaUnsaturated acyl AC to. acyl ACP
  3. HMG CoA-Reductase
  4. Folate reductase
  5. Phenylalanine hydroxylase ( to tyrosine)
  6. Meth Hb to Hb
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24
Q

Pellagra is found more in ______gender

It’s features

A

Females due to inhibitory influence of estrogen on tryptophan metabolism

  1. Dermatitis (cassals necklace)
  2. Diarrhoea
  3. Dementia
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25
Daily requirement of niacin
20mg | 5mg higher during lactation
26
Panthothenic acid(pan =>everywhere )
Co-A Deficiency (rare) => Gopalan burning foot syndrome RDA 10mg/day
27
Biotin requiring carbon fixation reactions
1. Acetyl Co-A carboxylase in FA biosynthesis 2. Propionyl Co-A carboxylase 3. Pyruvate carboxylase for OAA synthesis(TCA) and for gluconeogenesis
28
Carboxylation reactions where biotin is NOT required
1. CPS 1 and 2 for urea and pyrimidine synthesis 2. C6 of purine 3. Malic enzyme
29
Biotin cycle
Holocarboxylase synthetase + biotinidase Deficiency Multiple carboxylase Deficiency CNS involvements Tomcat urine odour Hair and skin disorder
30
Raw eggs and biotin
Has Avidin which binds to B7 Pyruvate carboxylase decreases Hypoglycaemia Rx B7
31
RDA of biotin B7
200-300mg/day
32
Folic acid is absorbed in _____
Upper parts of jejunum ,transported through blood via beta globulins
33
Causes of folate deficiency (one of the most common )
1. Pregnancy 2. Drugs 3. Defective absorption 4. Haemolytic anaemia (demand increases) 5. Dietary deficiency 6. Folate trap(B12 deficiency)
34
Holocarboxylase
Bit B7(biotin ) + carboxylase
35
Manifestations of folate deficiency
1. DNA synthesis Decreases (thymine synthesis decreases ) 2. Macrocytic anaemia (not megaloblastic and without neurological symptoms ) 3. Hyperhomocysteinuria which leads to 4. Birth defects 5. Cancer
36
Assessment of folate deficiency
1. Blood level 2. Histidine load test( FIGLU test) 3. AICAR excretion test( pyrimidine synthesis decreases ) 4. Peripheral blood press
37
RDA of folate
Adults 200 mg/day Pregnancy 400 mg/day Lactation 300 mg/day
38
Eg of anti vitamins
Dicoumarol Methotrexate (folic acid) Isoniazid (pyridoxine)
39
Forms of B12
``` Oral(lab) :cyano Injections :hydroxy Functional forms are Storage: DeoxyAdenosyl (liver , somatic) Transport(blood) :Methyl ```
40
Second factor of B12 or cobalophilin is secreted from
Saliva
41
Functions of vitamin B12
1. Methyl Malonate Co-A isomerase of odd chain fatty acids 2. Methionine synthase or homocysteine methyl transferase 3. Demethylation of methyl THFA
42
Causes of vitamin B12 deficiency
1. Diet 2. Decreased absorption 3. Addisonian pernicious anaemia 4. Gastric atrophy 5. Pregnancy 6. Fish tapeworm
43
Deficiency manifestations of vitamin B12
1. Folate trap 2. Megaloblastic anaemia 3. Homocysteinuria 4. Demyelination due to SAM 5. Subacute combined degeneration 6. Achlorhydria
44
Assessment of vitamin B12 deficiency
1. Serum B12 levels 2. Schilling test 3. Methyl malonic acid 4. Blood smear 5. Homocysteinuria 6. FIGLU test
45
RDA of B12
1-2 microgram/day | 2 microgram/day for pregnancy and lactation
46
Functions of vitamin C
1. Redox and antioxidant 2. Hydroxylation of proline and lysine for collagen 3. Hydroxylation of tryptophan for serotonin 4. Tyrosine metabolism 5. Iron absorption via reduction 6. MetHb reduction 7. Helping folate reductase( thus RBC maturation ) 8. Steroidogenesis 9. Stimulates phagocytosis 10. Cataract
47
Barlow disease
Infantile scurvy | Vitamin C supplementation required between 6 & 12 months ( Breast milk)
48
Vitamin C deficiency and anaemia ?
Microcytic hypochromic anaemia due to 1. Loss of blood via haemorrhage 2. Decreased Iron absorption 3. Decreased THFA 4. Increased MethHb
49
RDA of vitamin C
75mg/day Pregnancy and lactation 100mg/day For smokers and those on contraceptive pills > 100 mg/day
50
Toxic water soluble vitamins are
Vitamin B6 and niacin
51
Retinoids are found in __ sources
Animal
52
Eg of carotenoids
Lutein, zeaxanthin(Rx of macular degeneration ) Lycopene (Rx of prostate cancer) Beta carotene ( antioxidant )
53
Different forms of retinoids acid
All trans 9 cis 13 cis In regulation of gene expression (growth and development , Tissue differentiation)
54
Retinol structure
Beta ionone ring + isoprenoid chain
55
Absorption and storage of vitamin A
Retinol ester is split and retinol is absorbed Deoxygenase of intestinal cells split absorbed carotenoid These are esterified in these cells The retinal esters are carried by chylomicron In the liver they are stored in the peri sinusoidal cells (Ito cells)
56
Vitamin A is transported in the form of a
Ternary complex | Retinol + RBP + Transthyretin
57
Metarhodopsin II
It activates the signal cascade pathway ``` GPCR-transducin is activated Phosphodiesterase activated cGMP to 5’GMP closes Na+ channel Hyperpolarisation ```
58
RAR
Retinoids acid receptor | All trans retinoids acid ligand
59
RXR. Why vitamin D or thyroid deficiency causes vitamin A deficiency
Retinoic acid X receptor 9 cis retinoic acid It dimerises with vitamin D receptor complex,(thyroid hormone complex,...) Heterodimer Then binds
60
Earliest sign (not symptom)of Vitamin A deficiency
Loss of sensitivity to green light Earliest symptom is nyctalopia
61
Skin effects of vitamin A deficiency
``` Follicular hyperkeratosis (phrynoderma or toad skin) Also caused by EFA deficiency ``` Squamous metaplasia( UTI & RTI) Blockage of adnexal glands
62
Toxicity of vitamin A
Rare Seen in arctic explorers due to polar bear liver Affects lysosomes Acute 1 pseudotumor cerebri (head ache, vomitting,blurry vision) 2 exfoliating dermatitis Chronic Weight loss ,nausea, bony exostosis, Joint pain, increases osteoclastic activity(hip fractures)
63
Therapeutic application of vitamin A
``` Beta carotene( cutaneous photosensitivity) 2. All trans retinoic acid( tretinoin)- mild acne, acute promylocytic leukaemia ( differentiation therapy) ```
64
13cis retinoic acid
Isotretinoin Teratogenic Used in cystic acne(severe) , childhood neuroblastoma
65
Vitamin D eg
Vitamin D2 ergocalciferol (plant origin) | Vitamin D3 cholecalciferol (calciol)
66
Dietary source of vitamin D is
Fish (Halibut liver oil) Vitamin D fortified Rest is negligible
67
Transport protein of D3 and the first hydroxylation
D Binding Protein(DBP) which goes to the liver where it is hydroxylated by 25 Hydroxylase (part of cytochrome p450) to calcidiol or 25 OH D3
68
Hydroxylation in the kidney of calcidiol
By 1 alpha hydroxylase (favoured by PTH) it is converted to 1,25 dihydroxy cholecalciferol or calcitriol This is the RDS
69
UV. light responsible for isomerisatiom of 7 dehydrocholesterol to cholecalciferol
UV -B | 290-315 nm
70
Inactivation of calcidiol and calcitriol is by
24 hydroxylation to | 24 calcidiol and calcitetrol
71
Functions of vitamin D
1. Regulation of Ca and P 2. Immunomodulatory 3. Antiproliferative 4. Bone mineralization during bone development
72
Phosphorus level in serum increasing substances
Vitamin D
73
Regulation of Ca in intestine
Vitamin D increases 1. Calcium transport channel TRPV6 2. calbindin 9K
74
Regulation of Ca in kidneys
PTH increases hydroxylation of calcidiol in DCT Vitamin D then increases 1. TRPV 5 2. Calbindin 28K Thus increases both Ca and P reabsorption But PTH increases excretion of P while increasing Ca reabsorption
75
Regulation of Ca in bones by vitamin D and PTH
Increases action of RANK ligand (receptor activator NFKB Ligand) located on osteoblasts Whose receptor is located on proosteoclasts Thus increases maturation of osteoclasts
76
Vitamin D and tuberculosis
Few I alpha hydrxylation occurs in the macrophages by cytochrome p27B Toll like receptor binds to the bacteria which increases cytochrome p27B Calcitriol increases which increases cathelicidin which kills the bacteria
77
Holy grail of cancer medicine is vitamin D
If vitamin D level is less than 20 no/ml it is associated with increased colon,breast and prostate cancers It is also protective against prediabetes and metabolic syndrome
78
Contrary to normal state vitamin D during bone development increases
1. Osteoclastic activity 2. Mineralisation of bone 3. Osteocalcin (mineralization) Thus vitamin D deficiency during infant causes poor mineralization of osteoid leading to rickets
79
Rickets
Rachitic rosary Wind swept deformity Harrison’s sulcus
80
Nutritional rickets
``` Nutritional deficiency or decreased sunlight exposure Serum Ca decreases But, Secondary hyperparathyroidism 1 alpha hydroxylation increases Then vitamin D3 is normalised Then serum Ca is normalised But serum phosphate level will be reduced ```
81
Toxicity of vitamin D
4000 IU in infants > 50 mg/day Deposition of Ca in soft tissues and blood vessels (contraction of blood vessels and hypertension) Metastatic calcification Calcinosis
82
Assay of vitamin D
25 hydroxy cholecalciferol Ideal level 20-100 ng/mL Serum osteocalcin
83
Vitamin E most potent active form is
Alpha tocopherol | Vitamin E has chromate ring with isoprenoid unit (seen in A,E,K)
84
Antioxidant Functions of vitamin E
1. Chain breaking antioxidant 2. Prevents oxidation of PUFA in the membrane 3. Prevents oxidation of LDL
85
Deficiency manifestations of Vitamin E
1. Axonal degeneration (posterior column affected and hence decreased position and vibration sense) 2. Spinocerebellar symptoms (ataxia) 3. Peripheral neuropathy 4. Skeletal myopathy 5. Pigmented retinopathy 6. Ophthalmoplegia
86
Features of the least toxic fat soluble vitamin
Vitamin E 1. Decreases platelet aggregation 2. Interferes with vitamin K
87
Sources of vitamin E
Wheat germ oil Cotton seed oil Sunflower oil
88
High doses of vitamin E is used for
1. Retrolentil fibroplasia 2. Bronchopulmonary dysplasia 3. Intraventricular haemorrhage 4. Intermittent claudication
89
Structure of vitamin K
Naphthoquinone derivative + isoprenoid chain
90
Forms of vitamin K
K1 phylloquinone plant sources K2 Menaquinone intestinal flora K3 menadione synthetic - water soluble form of a fat soluble vitamin
91
Action of vitamin K on clotting factors
Vitamin K gamma carboxylase 2,7,9,10 for Ca binding and itself is converted to vitamin K epoxide. It is converted back by vitamin K epoxide reductase ( inhibited by warfarin, dicoumarol)
92
Proteins that are affected by vitamin K (gamma carboxylation)
1. Protein C, protein S 2. Osteocalcin and nephrocalcin 3. Product of gas 6 gene (gene arrest specific) 4. Matrix gla protein
93
ABC enzymes
ATP dependent Biotin Carboxylation
94
Deficiency of vitamin K
Increases 1. Bleeding time 2. Prothrombin time
95
Reasons why vitamin K deficiency occurs in premature infants
1. Immaturity of liver 2. Sterile gut 3. Breast milk poor in vitamin K 4. Poor placental transport 5. Low body stores
96
Increased vitamin K causes
Hemolysis ( deficiency of vitamin E causes the same) Jaundice Hyperbilirubinemia Kernicterus and brain damage

Biochemistry MBBS (10 decks)

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