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Preventative Med. & Nutrition > Exam #1: Water Soluble Vitamins > Flashcards

Exam #1: Water Soluble Vitamins Flashcards

1
Q

What are the two major types of vitamins?

A

Water-soluble

Fat soluble

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2
Q

What form of vitamins has a higher risk for toxicity? Why?

A
  • Fat soluble b/c they are stored unlike water-soluble vitamins

**Note that water soluble vitamins wash-out from the body EXCEPT B12 & Folate, which are stored in the liver

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3
Q

What is the DRI?

A

Dietary Reference Intake

- Set of reference values to plan and assess nutrient intake of healthy people

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4
Q

What is the RDA?

A

Recommended Dietary Allowance

- Average daily level of intake for nearly all healthy people

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5
Q

What is the AI?

A

Adequate Intake

- Established when insufficient evidence for RDA- assumed to ensure nutritional adequacy

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6
Q

What is the EAR?

A

Estimated Average Requirement

- Expected to satisfy the needs of 50% of people in that age group

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7
Q

How does the DRI vary with age and gender?

A

General increase with age & gender

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8
Q

What is the TUL?

A

Tolerable Upper Limit

- Max daily intake unlikely to have harmful consequences

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9
Q

What are the two major classes of water soluble vitamins?

A

Vitamin C

Vitamin B

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10
Q

List the major functions of Vitamin C.

A

1) Antioxidant
2) Reduces iron AND necessary for absorption of non-heme iron
3) Hydroxylates proline and lysine= COLLAGEN SYNTHESIS
4) Dopamine Beta-Hydroxylase

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11
Q

What is unique about Vitamin C?

A

Not a coenzyme

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12
Q

How are B Vitamins involved in energy production?

A
  • Involved in metabolism of energy-yielding nutrients
  • Coenzymes

**NOT involved in rate-limiting steps

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13
Q

List the hematopoietic B Vitamins.

A
  • B6, PLP
  • B9, Folic acid
  • B12, Cobalamin
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14
Q

What is the function of Vitamin B6 (PLP)?

A

1) Transamination
2) Decarboxylation
3) Cystathione Synthase
4) Heme synthesis
5) Niacin synthesis from Tryptophan (W)

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15
Q

What is the function of B1 (Thamine)?

A

Thiamine is a cofactor for dehydrogenase enzyme reactions that produce ATP:

1) Branched chain amino acid dehydrogenase
2) Pyruvate dehydrogenase
3) A-ketoglutarate dehydrogenase
4) Transketolase

Deficiency leads to severe ATP depletion that affects aerobic tissues first, i.e. brain and heart.
- Worsened by glucose infusion.

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16
Q

What is the function of folic acid?

A
  • Folate is converted to THF, a coenzyme for 1-C transfer/methylation rxn

Important for DNA & RNA synthesis

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17
Q

What are the four general functions of B12? What are the two specific enzymes it is a cofactor for?

A

1) DNA synthesis
2) FA synthesis
3) Energy production
4) Myelin sheath production

  • Cofactor for methionine synthase (homocystine to methionine) and methylmalonyl-CoA mutase (methylmalonyl CoA to succinyl-CoA
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18
Q

What is the function of Niacin?

A
  • Niacin is a constituent of NAD+ and NADP+ that are used in redox reactions
  • Therapeutically, Niacin is used to treat dyslipidemia
19
Q

What is the function of the Folate/B12 one carbon metabolism pathway?

A

Generally, Folate and B12 generate and transfer one carbon groups necessary for the methylation of DNA

Specifically, B12:

  • Regenerates THF from MTHF
  • Methyl-B12 donates it’s methyl group to homocysteine, forming methionine
  • Is important for odd chain FA synthesis (crucial to myelin production)
20
Q

What does a B12 deficiency lead to?

A

1) Macrocytic megaloblastic anemia
2) Hypersegmented neutrophils
3) Neurologic deficits
- Posterior columns
- Lateral corticospinal tracts
- Spinocerebellar tracts
4) “Methyl trap” in methylation pathway i.e. methyl trapped as MTHF

21
Q

What does a folate deficiency result in?

A
  • Macrocytic megaloblastic anemia

- Neural tube defects

22
Q

Draw the Folate/ B12 methylation pathway.

A

N/A

23
Q

List the important structural features of B12 (Cobalamin).

A
  • Cobalt ion complexed in ring structure

- R group attaches to methyl group to yield “methylcobalamin”

24
Q

Where does B12 come from?

A

Animal sources ONLY

25
Q

Outline the six major steps of B12 metabolism.

A

1) Oral= R proteins needed for absorption
2) Gastric
- Low pH releases B12 from dietary protein to bind R proteins
- Parietal cells release intrinsic factor (IF)
3) Luminal= pancreatic proteases degrade R proteins so B12 can bind IF
4) Mucosal= B12-IF complex binds receptor in terminal ileum
5) Transport= transported in blood bound to “transcobalamin”
6) Excretion=
- Excreted into bile
- Most rebinds IF for recycling

26
Q

What are the causes of B12 deficiency?

A

1) Pernicious anemia
2) Gastrectomy/ bariatric surgery
3) Malabsorption syndrome
4) Celiac sprue
5) Enteritis
6) Chron’s Disease
7) Diphylobothrium Latum

27
Q

What is the Schilling test? What is the purpose of this test?

A

Measures B12 & IF deficiency

28
Q

What is the difference between the presentation of folate and cobalamin deficiency?

A

B12 is associated with cognitive impairment and neurologic deficits

29
Q

What does folate deficiency in the 1st trimester lead to an increased risk of?

A

NTDs

30
Q

What is Dry Beriberi? What are the symptoms?

A

Thiamine deficiency typically in older adults from low carb & energy intake that is characterized by:

1) Muscle wasting
2) Symmetric polyneuritis w/
- Wrist/ foot drop
- Loss of tendon reflexes
- Paresthesias

31
Q

What is Wet Beriberi? What are the symptoms?

A

Thamine deficiency associated with higher carb intake & physical activity that is characterized by:

  • Dilated cardiomyopathy
  • Edema
32
Q

What is Infantile Beriberi

A

Thiamine deficiency in infant from breastfeeding mother with low thiamine intake that causes:

  • Dyspnea
  • Cyanosis
  • Heart failure
33
Q

What is Wernicke - Korsakoff Syndrome?

A

Thiamine (B1) deficiency associated with alcoholism.

Wernike=

1) Confusion
2) Opthalmoplegia
3) Ataxia

Korsakoff=

1) Confabulation
2) Personality change
3) Memory loss

BOTH have damage to the medial dorsal nucleus and mammillary bodies of the hypothalamus

34
Q

What patient populations are at risk for scurvy today?

A

Surgical and burn patients

35
Q

What is Scurvy? What are the four H’s of scurvy?

A

Scurvy is a Vitamin C deficiency that leads to:

1) Bleeding/ swollen gums
2) Bruising
3) Impaired wound healing
4) Hemarthrosis
5) Perifollicular hemorrhages

The so called, “4-H’s of Scurvy” include:

1) Hemorrhage
2) Hyperkeratosis
3) Hypochondriasis
4) Hematologic abnormalities

36
Q

What are the two major causes of Biotin deficiency?

A

1) Raw egg ingestion
2) Chronic antibiotic therapy

*Remember “AVIDin in egg whites AVIDly binds biotin”

37
Q

What are the symptoms of biotin deficiency?

A
  • Dermatitis
  • Alopecia
  • Enteritis
38
Q

A deficiency in what vitamin leads to “Burning Feet Syndrome?”

A

Pantothenic Acid (B5)

39
Q

What does Riboflavin deficiency mimic?

A

Pellagra

*****Also remember, deficiency= 2x C’s of B2
o Cheilosis
o Corneal vascularization

40
Q

What are the three common causes of Niacin deficiency?

A

o Hartnup Disease (decreased tryptophan absorption)
o Malignant carcinoid syndrome (increased tryptophan metabolism)
o Isoniazid admin. (decreased B6)

*****Recall, Niacin is derived from tryptophan & requires B2 & B6 for synthesis

41
Q

What disease is caused by a Niacin deficiency?

A

Pellagra

42
Q

What are the four D’s of Pellagra?

A

Dermatitis
Dementia
Diarrhea
Death

43
Q

What are the two common causes of B6 deficiency?

A

1) Isoniazid

2) Oral contraceptives

44
Q

What are the symptoms of B6 deficiency?

A

1) Seizures
2) Hyper-irritability
3) Peripheral neuropathy
4) Sideroblastic anemia

Preventative Med. & Nutrition (30 decks)

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