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BIOL21361 Haematology > 6. Vit B12 and folate > Flashcards

6. Vit B12 and folate Flashcards

1
Q

why do we need B12

A
  • maintain function of brain and nervous system
  • formation of blood cells
  • involvde in metabolism of most cells
  • key role in DNA synthesis/regulation
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2
Q

how is gastric acid important for B12 absorption

A

allows b12 to be released from food
can be accessible for absorption

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3
Q

what is haptocorrin

A

(type of transcobalamin) binds B12 to form haptocorrin-B12 complex
acts as carrier protein
= serves to protect it from degradation by stomach acid

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4
Q

where is intrinsic factor released from

A

gastric parietal cells

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5
Q

where does B12/IF complex move to

A

ileum

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6
Q

is IF recycled

A

no
constantly need to produce more

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7
Q

how would B12 get to target cell

A

is carried in circulation by transcobalamin
- lysosomal degradation of TC
- release of B12

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8
Q

vitamin B6 other name

A

pyridoxine

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9
Q

what does B6 do

A

convert succinyl coA and glycine into ALA (aminolevulinic acid)

(ALA then turns into haem)

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9
Q

what does B12 do in process of making haem

A

convert methymalonyl- coA into succinyl coA

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10
Q

what other metabolic process does B12 act as a cofactor for

A

converts homocysteine to methionine

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11
Q

how much B12 needed a day

A

1-3 micrograms

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12
Q

where is B12 sotred

A

liver
3-5mg stored
(takes a while to get deficient)

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13
Q

loss of B12

A

urine and faeces
desquamation of epithelial cells
(normal excretion)

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14
Q

vitamin B9

A

folate

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14
Q

how do we get folate

A

incapable of synthesizing it
so must come from diet

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15
Q

bakers yeast?

A

study doen in 30s
- giving bakers yeast= corrected anaemia in pregnant women
- wasnt known what exaclty it was
- but knew it was necassary for healthy blood cell production

16
Q

what does be reduced to for it to be used

A

tetrahydrofolate
(the acitve form)

17
Q

what does tetrahydrofolate get converted to

A

methyltetrahydrofolate
which is then used in nucleic acid synthesis

18
Q

which precursors of DNA is folate responsible for

A

purine and pyrimidine precursors

19
Q

how can veganism cause B12 def

A

no B12 in plants

20
Q

what is pernicious anaemia

A

impaired absorption of B12, not because of a lack of b12, but a lack of functioning intrinsic factor

21
Q

causes of folate deficiency

A
  • poor dietry habits = chronic alcoholics or drugs can affect folate metabolism
  • Crohns disease, or other diseases that impacts absorption in GI tract
  • increased demand = e.g. MAINLY pregnancy, growth
  • anticonvulsants (need to consider if pregnant woman taking them )
21
Q

when does neural tube close

A

~ 28th day of pregnancy
nervous system develops

(because is so early, suggest supplements be taken before conception where possibile)

22
Q

folate or B12 deficiency in early pregancy causes:

A

spina bifida ( neural tube defects) due to need for folate and B12 when cells rapidly proliferating

23
Q

neurological complications from folate and B12 deficiency

A

preogressive demyleination of nerve cells
(POSSIBLY from increase in methylmalonyl- coA)

24
Q

clinical features/symptoms of folate and B12 deficiency

A
  • neuropathhy
  • tingling in feet = difficulty in gait
  • glossitis
25
Q

what 2 haematological disorders do B12/folate deficiency cause

A
  • megaloblastic anaemia (folate)
  • pernicious anaemia (b12 def)
26
Q

why are cells megaloblastic

A

low folate reduces dUMP to dTMP conversion
so DNA synthesis is delayed
= protein synthesis continues cuz RNA not affected as much = cell division delayed, but cell grows regardless

27
Q

are megaloblasts fully fucntioning

A

no, not same amouont of O2 carried

28
Q

MCV in megaloblastic anaemia

A

> 90fL

29
Q

what is seen in blood film in meglaoblastic anaemia

A
  • less cell divisions
  • oval macrocytes
  • increased lobe number in neutrophils
30
Q

causes of pernicious anaemia

A
  • autoimmune attack on gastric mucosa
  • or genetic
31
Q

how can we test if pernicious anaemia is autimmune

A
  • antibody test
  • antibodies against gastric parietal cells are found in serum in 85% of patients
32
Q

what would you test for for pernicious anaemia

A

MCV increased
then test for methymalonyl- coA
(historically used Schilling method)

33
Q

pernicious anaemia treatment

A

vitamin B12 intramuscular injection
hydroxycobalamin

34
Q

how to treat meglaoblastic anaemia folate deficiency

A

oral dose of folic acid

35
Q

what must be ruled out before treating with folate and why

A

vit b12 deficiency must be ruled out
- anaemia can alleviate but neurologic deficits will not

36
Q

serum folate levels that suggest deficiency

A

<3micrograms /L

37
Q

B12 levels that suggest deficiency

A

< 200 pg/mL

38
Q
A

BIOL21361 Haematology (20 decks)

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