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Biochem 2 > Seminar 2. Vit B12 deficiency and methylmalonyl acidemia > Flashcards

Seminar 2. Vit B12 deficiency and methylmalonyl acidemia Flashcards

1
Q

What is anaemia?

A

where you have fewer red blood cells than normal or you have an abnormally low amount of a substance called haemoglobin in each red blood cell.

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2
Q

General symptoms of anaemia

A
  1. extreme tiredness (fatigue)
  2. lack of energy (lethargy) 3. breathlessness
  3. feeling faint
  4. headaches
  5. pale skin
  6. noticeable heartbeats (palpitations)
  7. hearing sounds coming from inside the body, rather than from an outside source (tinnitus)
  8. loss of appetite and weight loss
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3
Q

Symptoms of vitamin B12 deficiency

A
  1. a pale yellow tinge to your skin
  2. a sore and red tongue (glossitis)
  3. mouth ulcers
  4. pins and needles (paraesthesia)
  5. changes in the way that you walk and move around
  6. disturbed vision
  7. irritability
  8. depression
  9. changes in the way you think, feel and behave
  10. a decline in your mental abilities, such as memory, understanding and judgement (dementia)
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4
Q

Which chemical group does Vitamin B12 (cobalamin) belong to?

A

one of a group of complex molecules with a cobalt‐containing corrin ring synthesized only by microorganisms.

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5
Q

Vitamin B12 (cobalamin) is one of a group of complex molecules with a cobalt‐containing corrin ring synthesized only by _____

A

microorganisms.

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6
Q

The usual dietary source of vitamin B12 for omnivores is ___

A

flesh of other animal

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7
Q

An example that contains large amounts of vitamin B12

A

Faeces
-> waste matter remaining after food has been digested, discharged from the bowels; excrement.

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8
Q

What is the natural source of vitamin B12 for human?

A
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9
Q

What is the natural source of vitamin B12 for human?

A

animal‐origin food is the only natural food source of vitamin B12.

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10
Q

Does plant food provide B12 source?

A

NO!

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11
Q

Plant foods do not provide it unless the plant was exposed to ___

A

vitamin B12–producing bacteria

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12
Q

Plant foods do not provide it unless the plant was contaminated with ___

A

vitamin B12–containing substances (soil, insect parts, etc)

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13
Q

Plant foods do not provide it unless the plant was fortified with ___

A

vitamin B12 (e.g. fortified ready‐to‐eat breakfast cereals).

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14
Q

Example of foods high in vitamin B12

A

dairy products, meat, liver, fish, eggs, and shellfish

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15
Q

Vitamin B12 is bound to ____

A

proteins (enzymes) in food

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16
Q

Vitamin B12 must be released from ____ in the stomach by the action of HCl and pepsin.

A

dietary protein

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17
Q

Vitamin B12 must be released from dietary protein in the ____ by the action of HCl and pepsin.

A

stomach

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18
Q

Vitamin B12 must be released from ____ in the stomach by the action of ____ (2 things)

A

HCl and pepsin (gastric enzymes)

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19
Q

What are the 2 most common causes of vitamin B12 deficiency?

A

dietary deficiency and malabsorption

20
Q

What are the 2 pathways for absorption of vitamin B12?

A
  1. intrinsic factor associated
  2. passive diffusion.
21
Q

There are two pathways for absorption of vitaminB12, intrinsic factor associated and passive diffusion
-> Which pathway is the active process?

A

intrinsic factor associated

22
Q

Absorption of vitamin B12
-> What does the intrinsic factor associated pathway required?

A

It requires
- an intact stomach
- intrinsic factor
- pancreatic enzymes
- normally functioning terminal ileum

23
Q

There are two pathways for absorption of vitaminB12, intrinsic factor associated and passive diffusion
-> Which pathway is the active process?

A

intrinsic factor associated

24
Q

Vitamin B12 must be released from dietary protein in the stomach by the action of HCl and pepsin
-> The released free vitamin B12 then binds to ____

A

R protein

25
Q

What is R protein?

A

a haptocorrin produced by the salivary glands (free cobalamin has a very low solubility in water phase).

26
Q

The released free vitamin B12 then binds to R protein, a haptocorrin produced by the salivary glands (free cobalamin has a very low solubility in water phase).
-> R protein is degraded by ____

A

pancreatic enzymes in the alkaline environment of the small intestine

27
Q

The released free vitamin B12 then binds to R protein, a haptocorrin produced by the salivary glands (free cobalamin has a very low solubility in water phase).
-> R protein is degraded by pancreatic enzymes in the ____ (alkaline/acidic) environment of the small intestine

A

alkaline

28
Q

R protein is degraded by pancreatic enzymes in the alkaline environment of the small intestine
-> thus releasing vitamin B12 from R protein to form ____

A

the vitamin B12–intrinsic factor complex.

29
Q

What is Intrinsic factor?

A

a 60‐kDa glycoprotein that is secreted by gastric parietal cells after stimulation by food.

30
Q

Intrinsic factor is a 60‐kDa glycoprotein that is secreted by ____ after stimulation by food

A

gastric parietal cells

31
Q

Is the vitamin B12–intrinsic factor complex stable?

A

YES

32
Q

the vitamin B12–intrinsic factor complex is stable and proceeds to ____

A

the ileum

33
Q

Once formed, the vitamin B12–intrinsic factor complex is stable and proceeds to the ileum
-> What will happen to this complex?

A

The vitamin B12–intrinsic factor complex is attached to specific membrane receptors of the ileum
-> then it is absorbed by endocytosis.

34
Q

Can the intrinsic factor–related process has high capacity for absorbing vitamin B12?

A

this intrinsic factor–related process has a limited capacity for absorbing vitamin B12, with a maximum of 3 μg at one meal.
(large amount can be achieved by passive diffusion)

35
Q

Which Vit B12 absorption pathway is necessary for large quantities of vit B12?

A

Passive diffusion

36
Q

The rate of absorption by the passive process is less than ___ (percentage) of the ingested amount of vitamin B12.

A

1%

37
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and ______, the intrinsic factor is degraded by the lysosomal proteases and cobalamin is bound by transcobalamin‐II (TC‐II)

A

fusion of the endosomes and lysosomes

38
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and fusion of the endosomes and lysosomes, the intrinsic factor is degraded by _____

A

the lysosomal proteases

39
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and ______, the intrinsic factor is degraded by the lysosomal proteases and cobalamin is bound by transcobalamin‐II (TC‐II)

A

fusion of the endosomes and lysosomes

40
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and fusion of the endosomes and lysosomes
-> the intrinsic factor is degraded by the lysosomal proteases
-> cobalamin is bound by ____

A

transcobalamin‐II (TC‐II)

41
Q

What is transcobalamin‐II (TC‐II)?

A

a protein structurally related to the intrinsic factor, but produced by the intestinal epithelial cells

42
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and fusion of the endosomes and lysosomes, the intrinsic factor is degraded by the lysosomal proteases and cobalamin is bound by transcobalamin‐II (TC‐II)
-> The TC‐II‐B12 complex is secreted in ____

A

the circulation

43
Q

Following the endocytosis of the vitamin B12–intrinsic factor complex and fusion of the endosomes and lysosomes, the intrinsic factor is degraded by the lysosomal proteases and cobalamin is bound by transcobalamin‐II (TC‐II)
-> The TC‐II‐B12 complex is secreted in the circulation
-> This complex is then taken up by ___

A

TC‐II‐receptor mediated endocytosis in the tissues

44
Q

The TC‐II‐B12 complex is secreted in the circulation and taken up by TC‐II‐receptor mediated endocytosis in the tissues
-> What happen to cobalamin at this point?

A

cobalamin is converted to its methyl and adenosyl derivatives that serve as enzyme cofactors.

45
Q

ranscobalamin‐II (TC‐II), a protein structurally related to ____, but produced by the intestinal epithelial cells

A

the intrinsic factor

46
Q

Perturbation of cobalamin absorption
-> What is pernicious anemia associated with gastric atrophy?

A

Pernicious anemia is the end stage of autoimmune gastritis (type A chronic atrophic gastritis or gastric atrophy) in which both the fundus and body of the stomach are involved.

47
Q

Pernicious anemia is the end stage of autoimmune gastritis (type A chronic atrophic gastritis or gastric atrophy) in which both ___ and ___ are involved

A

the fundus and body of the stomach

Biochem 2 (38 decks)

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