Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

HUNT 241 > Lecture 3 - Vitamin B12 > Flashcards

Lecture 3 - Vitamin B12 Flashcards

(61 cards)

Start Studying
1
Q

what food group is a rich source of vitamin B12

A

animal products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why is vitamin B12 fortification very important for vegans

A

they do not consume animal products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why is marmite not a very good source of vitamin B12

A

although there is a lot of B12 in marmite per 100 grams, we don’t consume enough for this to be an adequate source of B12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is another issue with marmite and why it isnt a very good source of vitamin B12

A

very high in sodium, so if over consumed have negative health effects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

where does vitamin B12 actually come from

A

bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how does B12 get into the foods we eat

A

bacteria produce B12 in the cow (has to do with their rumen) this goes into our meat and milk

also fish and chicken have B12

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

commercial production of vitamin B12 happens how

A

large scale production via microbial fermentation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

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

A

three strains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Vitamin B12 is the term used for what

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

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

A

Big molecular weight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the chemical structure of vitamin B12

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what determines what type of corrinoid it is

A

whatever is bound to the colbalt in the centre of the corrin ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

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

A

cyanocobalamin

methylcobalamin

deoxyadenosylcobalamin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the active forms of B12

A

methylcobalamin

deoxyadenosylcobalamin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

cyanocobalamin

most common form used for supplements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is cobalamin very sensitive to

A

very sensitive to acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

cobalamin from the diet is bound to what

A

protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

as cobalamin is swallowed what is released at the same time

A

haptocorrin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
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)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what happens to cobalamin in the duodenum

A

proteases will split haptocorrin from the cobalamin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

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

A

more alkaline space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
what does your body need in order to absorb cobalamin
transporter that will enable it to bind to a receptor
26
what is the role of intrinsic factor regarding cobalamin
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
27
is B12 water soluble or water insoluble
water soluble
28
absorbed cobalamin is later what
later recycled after excreted in bile
29
what are two enzymes that are B12 dependent
methylmalonyl-CoA mutase methionine synthase
30
what is the role of methylmalonyl-CoA mutase enzyme
conversion of methylmalonyl CoA > succinyl CoA
31
what is the role of methionine synthase
transfer methyl group from 5MTHF to homocysteine, to form methionine
32
if you do not have enough vitamin B12, you will not have enough adenosylcobalamine and what does this mean
you will not have enough 1-Methylmalonyl-CoA mutase
33
if you have insufficient 1-Methylmalonyl-CoA mutase then what will you not be producing enough of and why is this important
succinyl-CoA = important in the citric acid cycle
34
if you have insufficient 1-Methylmalonyl-CoA mutase then you will have a build up of what and what will this produce more of
methylmalonyl-CoA, so more methylmalonic aicd will be produced
35
a build up of methylmalonyl-CoA also leads to a build up of propinoyl-CoA and what does this cause
propionic acid from gut flora odd chain fatty acids
36
what is the enzyme that converts a methyl group onto homocysteine to form methionine and when can this be inhibited
methionine synthase - when there is not enough B12 to support methionine synthase activity
37
in the methylfolate trap what will happen to the levels of 5MTHF and why
there will be higher levels, because can not go through the pathway due to methionine synthase problems
38
in the methylfolate trap what will happen to the levels of THF and why
there will be lower levels, the pathway is getting jammed up at 5MTHF, it can not get converted back to THF
39
in the methylfolate trap what will happen to the levels of 5,10-methylene THF and why
there will be lower levels, less THF so less being converted to 5,10-methylene THF
40
in the methylfolate trap what will happen to DNA synthesis
DNA synthesis will decrease
41
in history of viramin B12 in 1849 what were the complications described, was there treatment and was it fatal ?
clinical symptoms of pernicious (harmful in a gradual way) anaemia described - no treatment (vitamin B12 not discovered yet) - fatal
42
in history of viramin B12 in 1926 it was found eating what helped patients with pernicious anaemia
eating raw liver
43
when was vitamin B12 named
1948
44
what is pernicious anaemia
lack of intrinsic factor
45
lack of intrinsic factor is a what and what does this do
autoimmune disease = attacks parietal cells which limits or eliminates production of intrinsic factor
46
how is a vitamin B12 deficiency due to lack of intrinsic factor treated and why
treated with B12 intramuscular injection (because it will only be absorbed if there is intrinsic factor so have to inject B12)
47
how is B12 deficiency caused by lack of stomach acid (limited and absent) and what does this do
limited (hypochlorhydria) or absent (achlorhydria) production of HCL lessens B12 release from animal protein
48
lack of stomach acid related to vitamin B12 deficiency most commonly affects who
elderly
49
what are the two types of gastrointestinal damage that can lead to vitamin B12 deficiency
Crohn's disease Gastric bypass
50
what is crohn's disease
a type of inflammatory bowel disease which may inflame the small intestine and reduce B12 absorption
51
what is gastric bypass
procedures that reduce the stomach area secreting stomach acid which can lead to reduced B12 absorption
52
there are 12 inherited errors of metabolism that have been identified and these affect : (4) (are they manageable)
- intestinal absorption - transport in the blood - cellular uptake - intracellular metabolism some are manageable, some are incompatible with life
53
what infants are particularly susceptible to vitamin B12 deficiency
breastfed infants with vegan mothers
54
megaloblastic anaemia has to do with vitamin B12 because of whay
methylfolate trap
55
what is vitamin B12 neuropathy
"subacute combined degeneration of the cord" - demyelination of motor neurons
56
what are the symptoms of vitamin B12 neuropathy
- loss of position sense - spasms and weakness of lower limbs - cognitive changes - memory loss due to dementia - may be irreversible
57
what is the biochemistry to vitamin B12 neuropathy
impaired methylation of myelin basic protein due to deficient methionine synthase activity
58
what is the upper limit of vitamin B12
not possible to set - no evidence of harm from several hundred times the requirement
59
what is the EAR and RDI of vitamin B12 in adult men and women
EAR : 2.0μg/day RDI: 2.4μg/day
60
what is the eating and activity guidelines around plant based milk alternatives linked to B12, vitamin D and calcium
if choosing plant based milks choose products fortified with calcium, vitamin D and vitamin B12
61
what products are permitted to be fortified with B12 in NZ
- extracts of meat, vegetables or yeast - analogues of meat - legume protein containing foods

HUNT 241 (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions