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Biochemistry > Nutrition > Flashcards

Nutrition Flashcards

1
Q

Vitamin A: function

A

Antioxidant
Constituent of visual pigments (retinal)
Essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells)
Prevents squamous metaplasia
Used to treat measles and AML subtype M3
Found in: leafy vegetables and liver
Uses: oral isotretinoin to treat severe cystic acne; all-trans retinoic acid to treat acute promyelocytic leukemia

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2
Q

Vitamin A: deficiency

A 
Night blindness (nyctalopia)
Dry, scaly skin (xerosis cutis)
Corneal degeneration (keratomalacia)
Bitot spots on conjuctiva
immunosuppression
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3
Q

Vitamin A: excess/Toxicity

A

Acute toxicity: nausea, vomiting, vertigo and blurred vision
Chronic toxicity: slope is, dry skin, hepatic toxicity and enlargement, arthralgias, and pseudotumor cerebri
Teratogenic (isotretinoin) contraindicated in pregnancy

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4
Q

Vitamin D: function

A

D2=ergocalciferol (ingested from plants)
D3=cholecalciferol (consumed in milk, formed in sun-exposed skin - stratum basale)
25-OH D3=storage form
1,25-(OH)2 D3=calcitriol; active form
Function: increase intestinal absorption of calcium and phosphate, increase bone mineralization at low levels and increase bone resorption at higher levels

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5
Q

Vitamin D: Deficiency

A

Rickets in children (bone pain and deformity)
Osteomalacia in adults (bone pain and muscle weakness)
Hypokalemia tetany
Breastfed infants should receive oral vitamin D
Exacerbated by low sun exposure, pigmented skin, prematurity

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6
Q

Vitamin D: Excess/Toxicity

A

Hyper alexia, hypercalcuira, loss of appetite, stupor

Seen in granuloumatous disease (increased activation of VitD by epitheliod macrophages)

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7
Q

Vitamin E: Function

A

Function: antioxidant (protects RBCs and membranes from free radical damage)
Can enhance anticoagulant effects in warfarin

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8
Q

Vitamin E: Deficiency

A

Hemolytic anemia
Acanthocytosis
Muscle weakness
Posterior column and spins cerebellum tract demyelination
Neurological presentation may appear similar to VitB12 deficiency but without megaloblastic anemia, hyper segmented neutrophils or increased serum methylmalonic acid levels

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9
Q

Vitamin K: Function

A

Cofactor for the gamma-Carboxylation of glutamic acid residues on various proteins required for blood clotting
K is for Koagulation: necessary for the maturation of clotting factors II, VII, IX, X and proteins C & S
Warfarin - VitK antagonist

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10
Q

Vitamin K: Deficiency

A

Neonatal hemorrhage with increased PT and aPTT but normal bleeding time (have sterile intestines and are unable to synthesize VitK)
Can also occur after prolonged use of broad-spectrum antibiotics
Not in breast milk, neonates given vitamin K injection at birth to prevent hemorrhagic disease

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11
Q

Vitamins: Fat soluble

A

Vitamins A, D, E, K
Absorption dependent on gut and pancreas. Toxicity is more common than for water-soluble vitamins since they accumulate in the fat
Malabsorption syndromes with steatorrhea, such as cystic fibrosis or sprue, or mineral oil intake can cause deficiencies

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12
Q

Vitamins: water soluble

A 
All wash out easily from the body except B12&B9 (stored in liver)
B-complex deficiencies often result in dermatitis, glossitis and diarrhea
Can be co-enzymes (VitC) or precursors to organic cofactors (FAD, NAD+)
B1 (Thiamine: TTP)
B2 (riboflavin: FAD, FMN)
B3 (niacin: NAD+)
B5 (pantothenic acid: CoA)
B6 (pyridoxine: PLP)
B7 (biotin)
B9 (folate)
B12 (cobalamin)
C (ascorbic acid)
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13
Q

VitB1 (thiamine): function

A

In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions:
Pyruvate dehydrogenase (links glycolysis to TCA cycle)
Alpha-ketoglutarate dehydrogenase (TCA cycle)
Transketolase (HMP shunt)
Branched-chain ketoacid dehydrogenase
(Think ATP acronym)

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14
Q

VitB1 (thiamine): Deficiency

A

Impaired glucose break down - ATP depletion worsened by glucose infusion
Highly aerobic tissues (e.g brain & heart) are affected first
Wernicke-Korsakoff and beriberi
Seen in malnutrition and alcoholism
Diagnosis: increased RBC transketolase activity following VitB1 administration

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15
Q

Wernicke-Korsakoff syndrome

A 
VitB1 deficiency (alcoholism)
Classic triad: Confusion, opthalmoplegia, ataxia 
\+ confabulation, personality change, memory loss (permanent) 
Damage to medial dorsal nucleus of thalamus, mammillary bodies
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16
Q

Dry Beriberi

A

VitB1 deficiency

Polyneuritis, symmetrical muscle wasting

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17
Q

Wet Beriberi

A

VitB1 deficiency

High output cardiac failure (dilated cardiomyopathy), edema

18
Q

Vitamin B2 (riboflavin): Function

A

Component of flavins FAD & FMN, used as cofactors in redox reactions, e.g. The succinctness dehydrogenase reaction in the TCA cycle
FAD & FMN derived from riboFlavin (B2=2ATP)

19
Q

Vitamin B2 (riboflavin): deficiency

A

Cheilosis (inflammation of the lips, scaling and fissures at the corners of the mouth), Corneal vascularization
(2Cs of B2)

20
Q

Vitamin B3 (niacin): function

A

Constituent of NAD+, NADP+ (used in redox reactions)
Derived from tryptophan - synthesis requires B2 (riboflavin) and B6 (pyridoxine)
Used to treat dyslipidemia (lowers levels of VLDL and raises levels of HDL)
NAD derived from Niacin (B3=3ATP)

21
Q

Vitamin B3 (niacin): deficiency

A

Glossitis
Severe deficiency lead to pellagra which can be caused by Hartnup disease, malignant carcinoid syndrome (increased tryptophan metabolism), and isoniazid (decrease VitB6)
Symptoms of Pellagra (*3Ds of B3): Diarrhea, Dementia (or hallucinations), Dermatitis (C3/C4 dermatologist circumferential “broad collar” rash - Casal necklace), hyperpigmentation of sun exposed limbs

22
Q

Vitamin B3 (niacin): excess

A

Facial flushing (induced by PG, not histamine, can avoid by taking aspirin with niacin), hyperglycemia, hyperuricemia

23
Q

Hartnup Disease

A

AR
Deficiency of neutral amino acid (e.g tryptophan) transporters in proximal renal tubular cells and on enterocytes - neutral amino acidosis and decreased absorption from the gut - decreased tryptophan for conversion to niacin - pellagra like symptoms
Tx: high protein diet and nicotinic acid

24
Q

Vitamin B5 (pantothenic acid): function

A

Essential component of coenzyme A (CoA, a cofactor for acyl transfers) and fatty acid synthase
B5 is the “pento”thenic acid

25
Q

Vitamin B5 (pantothenic acid): deficiency

A

Dermatitis, enteritis, alopecia, adrenal insufficiency

26
Q

Vitamin B6 (pyridoxine): function

A

Converted to pyridoxal phosphate (PLP), a cofactor used in transamination (e.g. ALT and AST), decarboxylation reactions, glycogen phosphorylase
Synthesis of cystathionine, heme, niacin, histamine, and neurotransmitters including 5HT, Epi, NE, DA, & GABA

27
Q

Vitamin B6 (pyridoxine): deficiency

A

Convulsions, hyper irritability, peripheral neuropathy (deficiency inducible by isoniazid and oral contraceptives), sideroblastic anemias due to impair hemoglobin synthesis and iron excess

28
Q

Vitamin B7 (biotin): function

A

Cofactor for carboxylation enzymes (add one carbon group):

  1. Pyruvate carboxylase: pyruvate (3C) to oxaloacetate (4C)
  2. Acetyl-CoA carboxylase: acetyl-CoA (2C) to malonyl CoA (3C)
  3. Propionyl-CoA carboxylase: propionyl-CoA (3C) to methylmalonyl-CoA (4C)
29
Q

Vitamin B7 (biotin): deficiency

A

Relatively rare.
Dermatitis, alopecia, enteritis
Caused by antibiotic use or excessive ingestion of raw egg whites
Avidin in egg whites avidly binds biotin

30
Q

Vitamin B9 (folate): function

A

Converted into tetrahydrofolic acid (THF), a coenzyme for 1-carbon transfer/methylation reactions
Important in synthesis of nitrogenous bases in DNA and RNA
Found in leafy green vegetables (Folate from Foliage)
Absorbed in jejunum, small reserve pool stored in liver

31
Q

Vitamin B9 (folate): deficiency

A

Macrocyclic, megaloblastic anemia
Hypersegmented polymorphonuclear cells (PMNs)
No neurologic symptoms (as opposed to VitB12 deficiencies)
Labs: increased homocysteine, normal methylmalonic acid levels
Most common deficiency in US

32
Q

Vitamin B9 (folate): causes of deficiency

A 
Drugs
-phenytoin, sulfonamides, methotrexate
Alcoholism
Pregnancy
Supplemental maternal folic acid in early pregnancy decreases the risk of neural tube defects
33
Q

Vitamin B12 (cobalamin): function

A

Cofactor for methionine synthase (transfers CH3 groups as methylcobalamin) and methylmalonyl-CoA mutase
Synthesized only by microorganisms and found in animal products
Very large reserve pool (liver - years)

34
Q

Vitamin B12 (cobalamin): deficiency

A

Macrocytic, megaloblastic anemia; hypersegmented PMNs
Parasthesias and subacute combined degeneration (degeneration of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts) due to abnormal myelin
Associated with increased serum homocysteine and methylmalonic acid
Prolonged - irreversible nerve damage

35
Q

Vitamin B12 (cobalamin): causes of deficiency

A

Causes:
-malabsorption (sprue, enteritis, Diphyllobothrium lactum), lack of intrinsic factor (pernicious anemia - anti-IF Ab diagnostic), absence of terminal ileum (surgical resection for eg Crohn) or insufficient intake (veganism)

36
Q

Vitamin C (ascorbic acid): function

A

Antioxidant; also facilitates iron absorption by reducing it to Fe2+ state
Necessary for hydroxylation of proline and lysine in collagen synthesis
Necessary for DA beta-hydroxylase (converts DA to NE)
Found in fruits and vegetables
pronounce Absorb-ic acid
Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+

37
Q

Vitamin C (ascorbic acid): deficiency

A

Scurvy (VitC deficiency causes sCurvey due to a Collagen synthesis defect)
Swollen gums, bruising, petechiae, hemarthrosis, anemia, poor wound healing, perifollicular and subperiosteal hemorrhages, “corkscrew” hair
Weakened immune response

38
Q

Zinc: function

A

Mineral essential for the activity of 100+ enzymes, important in the formation of zinc fingers (transcription factor motif)

39
Q

Zinc: deficiency

A

Delayed wound healing, hypogonadism, decreased adult hair (axiallary, facial, pubic), dysgeusia, anosmia, acrodermatitis enteropathica
May predispose to alcoholic cirrhosis

40
Q

Malnutrition: Kwashiorkor

A

Protein malnutrition resulting in skin lesions, edema due to decreased plasma oncotic pressure, liver malfunction (fatty change due to decreased apolipoprotein synthesis)
Clinical picture: small child with swollen abdomen
results from a protein deficient MEAL - Malnutrion, Edema, Anemia, Liver

41
Q

Malnutrition: Marsmus

A

Total calorie malnutrition resulting in emancipation (tissue and muscle wasting, loss of subQ fat) +/- edema
Marsmus results in Muscle wasting

Biochemistry (6 decks)

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