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HUNT241 > Lecture 3- Vitamin B12 > Flashcards

Lecture 3- Vitamin B12 Flashcards

Vitamin B12

1
Q

what food group is a rich source of vitamin B12

A

animal products

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2
Q

why is vitamin B12 fortification very important for vegans

A

they do not consume animal products

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3
Q

why is marmite not a very good source of vitamin B12

A

If you are consuming marmite you would need large amounts of it which will have bad affects of sodium

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4
Q

where does vitamin B12 actually come from

A

bacteria

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5
Q

commercial production of vitamin B12 happens how

A

large scale production via microbial fermentation

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6
Q

commercial production of vitamin B12 predominantly uses how many strains of bacteria

A

three strains

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7
Q

Vitamin B12 is the term used for what

A

the term used for all corrinoids that have biological activity of “cyancobalamin”

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8
Q

what is the molecular weight if B12 like compared to other vitamins

A

Big molecular weight

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9
Q

what is the chemical structure of vitamin B12

A

corrin ring (4 pyrrole rings) with a colbalt in centre and dimethylbezimidazole nucleotide

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10
Q

what are three examples of corrinoids and what can be bound to the colbalt

A

These three are found in food
cyanocobalamin

methylcobalamin

deoxyadenosylcobalamin

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11
Q

what are the active forms of B12

A

methylcobalamin

deoxyadenosylcobalamin

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12
Q

what is the stable form of B12 and what is this used for

A

cyanocobalamin

most common form used for supplements

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13
Q

what is cobalamin very sensitive to

A

very sensitive to acid

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14
Q

what must happen to cobalamin and protein before it can be digested

A

cobalamin must be removed from protein for the body to use it

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15
Q

why is the removal of cobalamin from a protein problematic

A

because this is done by an acid and cobalamin is very sensitive to acid

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16
Q

cobalamin from the diet is bound to what

A

protein

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17
Q

as cobalamin is swallowed what is released at the same time

A

haptocorrin

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18
Q

what happens in the stomach to cobalamin and why is it volunerable

A

HCL is released and this breaks off the protein from cobalamin (vulnerable to attack by the acid)

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19
Q

what will haptocorrin do and what does this mean

A

will bind to B12

binding to the cobalamin as soon as it released from the protein, protects it from acid attack

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20
Q

what happens to cobalamin in the duodenum

A

proteases will split haptocorrin from the cobalamin

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21
Q

why is it fine for cobalamin to be unbound in the duodenum

A

more alkaline space

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22
Q

what does your body need in order to absorb cobalamin

A

transporter that will enable it to bind to a receptor

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23
Q

what is the role of intrinsic factor regarding cobalamin

A

intrinsic factor is released from the stomach, will bind to cobalamin in the duodenum and can transport it into the ileal cell through the receptor

24
Q

is B12 water soluble or water insoluble

A

water soluble

25
Q

absorbed cobalamin is later what

A

later recycled after excreted in bile

26
Q

what are two enzymes that are B12 dependent

A

methylmalonyl-CoA mutase

methionine synthase

27
Q

what is the role of methylmalonyl-CoA mutase enzyme

A

conversion of methylmalonyl CoA > succinyl CoA

28
Q

what is the role of methionine synthase

A

transfer methyl group from 5MTHF to homocysteine, to form methionine

29
Q

if you do not have enough vitamin B12, you will not have enough adenosylcobalamine (ADSB) and what does this mean

A

you will not have enough 1-Methylmalonyl-CoA mutase

30
Q

if you have insufficient 1-Methylmalonyl-CoA mutase then what will you not be producing enough of and why is this important

A

succinyl-CoA = important in the citric acid cycle

31
Q

if you have insufficient 1-Methylmalonyl-CoA mutase then you will have a build up of what and what will this produce more of

A

methylmalonyl-CoA, so more methylmalonic aicd will be produced

32
Q

a build up of methylmalonyl-CoA also leads to a build up of propinoyl-CoA and what does this cause

A

propionic acid from gut flora

odd chain fatty acids

33
Q

what is the enzyme that converts a methyl group onto homocysteine to form methionine and when can this be inhibited

A

methionine synthase - when there is not enough B12 to support methionine synthase activity

34
Q

in the methylfolate trap what will happen to the levels of 5MTHF and why

A

there will be higher levels, because can not go through the pathway due to methionine synthase problems

35
Q

in the methylfolate trap what will happen to the levels of THF and why

A

there will be lower levels, the pathway is getting jammed up at 5MTHF, it can not get converted back to THF

36
Q

in the methylfolate trap what will happen to the levels of 5,10-methylene THF and why

A

there will be lower levels, less THF so less being converted to 5,10-methylene THF

37
Q

in the methylfolate trap what will happen to DNA synthesis

A

DNA synthesis will decrease

38
Q

Q
in history of viramin B12 in 1849 what were the complications described, was there treatment and was it fatal ?

A

clinical symptoms of pernicious (harmful in a gradual way) anaemia described
- no treatment (vitamin B12 not discovered yet)
- fatal

39
Q

in history of viramin B12 in 1926 it was found eating what helped patients with pernicious anaemia

A

eating raw liver

40
Q

when was vitamin B12 named

A

1948

41
Q

what is pernicious anaemia

A

lack of intrinsic factor

42
Q

lack of intrinsic factor is a what and what does this do

A

autoimmune disease = attacks parietal cells which limits or eliminates production of intrinsic factor

43
Q

how is a vitamin B12 deficiency due to lack of intrinsic factor treated

A

treated with B12 intramuscular injection

44
Q

how is B12 deficiency caused by lack of stomach acid (limited and absent) and what does this do

A

limited (hypochlorhydria) or absent (achlorhydria) production of HCL

lessens B12 release from animal protein

45
Q

lack of stomach acid related to vitamin B12 deficiency most commonly affects who

A

elderly

46
Q

what are the two types of gastrointestinal damage that can lead to vitamin B12 deficiency

A

A
Crohn’s disease

Gastric bypass

47
Q

what is crohn’s disease

A

a type of inflammatory bowel disease which may inflame the small intestine and reduce B12 absorption

48
Q

what is gastric bypass

A

procedures that reduce the stomach area secreting stomach acid which can lead to reduced B12 absorption

49
Q

there are 12 inherited errors of metabolism that have been identified and these affect : (4) (are they manageable)

A
  • intestinal absorption
  • transport in the blood
  • cellular uptake
  • intracellular metabolism

some are manageable, some are incompatible with life

50
Q

what infants are particularly susceptible to vitamin B12 deficiency

A

breastfed infants with vegan mothers

51
Q

megaloblastic anaemia has to do with vitamin B12 because of why

A

methylfolate trap

52
Q

what is vitamin B12 neuropathy

A

“subacute combined degeneration of the cord”

demyelination of motor neurons

53
Q

what are the symptoms of vitamin B12 neuropathy

A
  • A loss of position sense
  • spasms and weakness of lower limbs
  • cognitive changes - memory loss due to dementia
  • may be irreversible
54
Q

what is the upper limit of vitamin B12

A

not possible to set

no evidence of harm from several hundred times the requirement

55
Q

what is the EAR and RDI of vitamin B12 in adult men and women

A

EAR : 2.0μg/day
RDI: 2.4μg/day

56
Q

what is the eating and activity guidelines around plant based milk alternatives linked to B12, vitamin D and calcium

A

if choosing plant based milks choose products fortified with calcium, vitamin D and vitamin B12

57
Q

what products are permitted to be fortified with B12 in NZ

A

extracts of meat, vegetables or yeast

analogues of meat

legume protein containing foods

HUNT241 (19 decks)

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