Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

USMLE Biochemistry > B vitamins > Flashcards

B vitamins Flashcards

You may prefer our related Brainscape-certified flashcards:
USMLE® Step 1 flashcards
1
Q

What vitamins are water soluble?

A

B vitamins and vit C

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

What are common symptoms of B Vitamin defocencies?

A

Greatest effect on rapidly growing tissues

  • Dermatitis
  • Glossitis
  • Diarrhea
  • Cheilitis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Cheilitis?

A

Breakdown of skin surrounding lip

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

What is the active form of Thiamine?

A

Thiamine pyrophosphate (TPP)

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

What is thiamine a co-factor for? (4)

A
  • Pyruvate dehydrogenase
  • a-ketoglutarate dehydrogenase (TCA)
  • a-ketoacid dehydrogenase (branched chain amino acid)
  • Transketolase (HMP shunt)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does Thiamine require to become Thiamine pyrophosphate?

A

ATP converted to AMP (2 phosphate groups lost)

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

What 3 enzymes make up the pyruvate dehydrogenase complex?

A
  • Pyruvate dehydrogenase (E1)

-

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

What are the 5 co-factors for the pyruvate dehydrogenase complex?

A
  • Thiamine (B1)
  • NAD+ (B2)
  • FAD+ (B3)
  • Coenzyme A (B5)
  • Lipoic acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does alpha-KG dehydrogenase create?

A

Succinyl-CoA (+ CO2 and NADH)

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

Deficiency of what enzyme causes Maple syrup urine disease?

A

Alpha ketoacid dehydrogenase

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

Transketolase transfers a carbon unit to create what?

A

Fructose-6-phosphate

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

Abnormality of transketolase can result in what disease?

A

Wernicke-Korsakoff syndrome

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

Describe Dry Beriberi syndrome?

A

Neurological and muscular

  • Polyneuritis
  • Muscle weakness

No edema (dry)

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

Describe Wet Beriberi syndrome?

A

Cardio related

  • Tachycardia
  • High output HF
  • Edema
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe Wernicke-Korsakoff syndrome?

A
  • Confusion, confabulation
  • Ataxia
  • Opthalmoplegia (blurry vision)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What patients typically get Beriberi syndrome?

A

Malnourished

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

Why do malnourished patients often require thiamine first before glucose?

A

If without thiamine

  • Glucose cannot be metabolised as thaimine is required for pyruvate dehydrogenase
  • Can then worsen Wernicke-Korsakoff
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does Riboflavin metabolise?

A

FAD

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

Riboflavin + Adenosine creates what?

A

FAD+

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

FAD+ accepts 2 electrons what does it become?

A

FADH2

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

What enzymes is FAD+ required by

A

Dehydrogenases

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

What metabolic process is FAD+ essential to?

A

ETC

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

What complex in the ETC riboflavin essential for synthesising?

A

Flavin mononucelotide (FMN)

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

What are the symptoms of riboflavin deficiency? (rare)

A
  • Dermatitis
  • Glossitis
  • cheilitis (inflammation of lips, cracks in corners of mouth)
  • Corneal vascularisation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Niacin used to synthesise what?

A

NADH NADPH

- ETC

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

NAD+ is required by what enzymes?

A

Dehydrogenases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Niacin can be synthesised from what amino acid?

A

Tryptophan

28
Q

Tryptophan to Niacin requires what vitamin as a cofactor?

A

B6

29
Q

What is Niacin found in?

What patients may get a deficiency?

A
  • Grains
  • Milk, meat, liver

Corn based diets -> deficiency

30
Q

What are the symptoms of Niacin deficiency (Pellagra)?

A
  • Diarrhea
  • Dermatitis
  • Dementia
  • Death
    4 Ds
31
Q

What are the skin findings in those with Pellagra?

A
  • Sun-exposed areas
  • Initially like bad sunburn
  • Blisters, scaling
  • Dorsal surfaces of hands
  • Face, neck, arms and feet
32
Q

What diseases/treatments can lead to Niacin deficiency?

A
  • INH therapy (TB)
  • Hartnup disease
  • Carcinoid syndrome
33
Q

How may INH therapy (isoniazid) (TB) cause niacin

A
  • Isoniazid -> decreased B6 activity

- B6 required to synthesise niacin from tryptophan

34
Q

What is Hartnup disease?

A

Absence of AA transporter in PCT

  • Loss of tryptophan in urine
  • > Niacin deficiency
35
Q

How is hartnup disease inherited?

A

AR

36
Q

How may carcinoid syndrome cause niacin deficiency?

A
  • Up to 70% of Tryptophan is converted to serotonin in carcinoid
  • Normally only ~ 1%
  • Tryptophan deficiency (pellagra) reported
37
Q

What vitamin may be given to treat hyperlipidemia?

A

Niacin

- Effects lipolysis directly (unrelated NAD/NADP)

38
Q

Excess niacin results in what symptom?

A

Facial flushing

- Stimulates release of prostaglandins in skin

39
Q

How may facial flushing be treated as a result of niacin treatment?

A
  • Aspirin (inhibits prostaglandin) prior to niacin

- Fades with time

40
Q

What is pantothenic acid essential in the synthesis of?

A

Coenzyme A

41
Q

What is coenzyme A (created by pantothenic acid) required by?

A
  • Dehydrogenase enzymes

- Acetyl-CoA

42
Q

Beta oxidation reaction (Fatty acids to fatty acyl CoA) in fatty acid metabolism requires what coenzyme and therefore what vitmain?

A

Coenzyme A

- Pantothenic acid

43
Q

B5 deficiency has what symptoms (v. rare)?

A
  • GI: N/V, cramps
  • Numbness, paresthesias (burning feet)
  • Necrosis of adrenal glands (animal studies)
44
Q

What are the different types of vit B6 and what are they all converted to?

A
  • Pyridoxine (plants)
  • Pyridoxal, pyridoxamine (animals)
  • All converted to pyridoxal phosphate
45
Q

B6 can be used as a cofactor for what reactions?

A
  • Aminotransferase reactions (amino acids)
  • Cysteine creation (Homocysteine -> Cystathionine thru Cystathionine Synthase)
  • Histamine synthesis
  • Glycogen breakdown
  • Niacin
  • Heme synthesis
46
Q

B6 plays a role in the pathways for

A

Neurotransmitters

47
Q

What is Histamine created from?

A

Histidine

48
Q

Histidine is converted to Histamine by what enzyme?

What does it require as a cofactor?

A

Histidine Decarboxylase (removes CO2)

Vitamin B6 as cofactor

49
Q

What enzyme in glycogen breakdown does B6 act as a cofactor for?

A

Glycogen phosphorylase

50
Q

B6 is required for the synthesis of what substance in heme synthesis?

A

y-aminolevulinic acid (ALA)

51
Q

Deficiency of B6 can cause what anemia?

A

Sideroblastic

- Iron cannot be incorporated into heme -> accumulates in cytoplasm

52
Q

How can Isoniazid cause B6 deficiency?

A

Similar to B6 structure so forms inactive pyridoxal phosphate

53
Q

What drug outside of isoniazid may cause B6 deficiency?

A

Oral contraceptives

54
Q

What are the symptoms of a pure B6 deficiency? (v. rare)

A

CNS symptoms

  • Seizures
  • Confusion
  • Neuropathy

Glossitis, oral ulcers

55
Q

What B-vitamin has a potential toxicity?

A

B6

56
Q

What are the symptoms of B6 toxicity?

A
  • Pain/numbness in legs

- Sometimes difficulty walking

57
Q

Biotin acts as a cofactor for what enzymes?

A

Carboxylation enzymes

- All add 1 carbon group via CO2

58
Q

What carboxylation enzymes does biotin act as a cofactoe for?

A
  • Pyruvate carboxylase
  • Acetyl-CoA carboxylase
  • Propionyl-CoA carboxylase
59
Q

All carboxylase enzymes require what?

A

ABC

  • ATP
  • Biotin
  • CO2
60
Q

Acetyl-CoA Carboxylase converts Acetyl CoA into what?

A

Malonyl-CoA

61
Q

What substances can be converted to Propionyl-CoA and subsequently into the TCA cycle?

A

Amino acids

  • Valine
  • Methionine
  • Isoleucine
  • Threonine

Odd chain fatty acids

VOMIT mnemonic

62
Q

Propionyl-CoA Carboxylase converts Propionyl into what?

A

Methylmalonyl-CoA

This is then converted to Succinyl-CoA

63
Q

How may one get Biotin deficiency? (v. rare)

A

Mass consumption of raw egg whites (avidin)

64
Q

What are the symptoms of Biotin deficiency?

A
  • Dermatitis
  • Glossitis
  • Loss of appetite
  • Nausea
65
Q

Where are B vitamins absorbed (except B12)?

A

Jejunum

USMLE Biochemistry (44 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions