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Flashcards in Biochemistry: Nutrition Deck (20):
1

Fat Soluble Vitamins

A, D, E, K

Absorption dependant on gut and pancreas.

  • Malabosorption syndromes (steatorrhea) such as cystic fibrosis and sprue or mineral oil intake can cause fat-souble vitamin deficiency
  • Toxicity is more common than in water soluble vitamins

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Water soluble vitamins

B1,B2,B3, B5,B6,B7,B9,B12

Vitamin C

  • All wash out easily from body except B12 and folate (stored in liver)
  • Deficiencies result in dermatitis, glossitis, diarrhea

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Vitamin A

  • Anti-oxidant
  • constituent of visual pigments (retinal)
  • Prevents squamous metaplasia
  • Used to treat measles, AML and subtype M3
  • Found in liver and leafy vegetables
  • Deficiency
    • Night blindness
    • dry, scaly skin, alopecia
    • corenal degeneration
    • immune suppression
  • Toxicity
    • Arthralgia
    • Skin changes, alopecia
    • cerebral edema
    • pseudotumor cerebi
    • osteoporosis
    • hepatic abnormalities
    • Teratogenic (cleft palate)

4

Vitamin B1

Thiamine

  • Thiamine pyrophosphate (TPP) is a co-factor for dehydrogenases
    • Pyruvate dehydrogenase
    • Alpha ketoglutarate dehydrogenase (TCA)
    • Transketolase (HMP shunt)
    • Branched chain ketoacid dehydrogenase
  • Deficiency
    • impaired glucose breakdown--> ATP depletion
    • highly aerobic tissues are affected first
    • Wernicke-Korsakhoff: confusion, opthalmoplegia, ataxia, personality change, memory loss
    • Dry Beriberi: polyneuritis, symmetrical muscle wasting
    • Wet Beriberi: high-output cardiac failure (dilated cardiomyopathy), edema

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Vitamin B2

Riboflavin

  • FAD & FMN
  • used as co-factors in redox reactions
    • succinate dehydrogenase in TCA
  • Deficiency
    • Cheilosis
    • Corneal vascularization

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Vitamin B3

Niacin

  • NAD, NADP
  • Used in redox reactions
  • derived from tryptophan
  • Used to treat dyslipidemia ( lowers VLDL and raises HDL)
  • Deficiency
    • Glossitis
    • Pellagra ( Diarrhea, Dementia, Dermatitis)
  • Excess
    • Facial flushing (induced by prostaglandins), hyperglycemia, hyperuricemia

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Vitamin B5

Pantothenate Acid

  • Component of CoA
    • ​co-factor for acyl transfers and fatty acid synthase
  • Deficiency
    • Dermatitis, enteritis, alopecia, adrenal insufficiency

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Vitamin B6

Pyridoxine

  • Pyridoxal Phosphate (PLP)
    • transamination reactions (ALT & AST)
    • decarboxylation reactions
    • glycogen phosphorylase
    • Synthesis of cystathionine, heme, niacin, histamine, neurotransmitters (epinephrine, noreepinephrine, dopamine, GABA)
  • Deficiency
    • Convulsions, hyperirritabiity, peripheral neuropathy, sideroblatic anemia due to impaired hemoglobin synthesis and iron excess
    • Deficiency inducible by isoniazid and oral contraceptives

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Vitamin B7

Biotin

  • Cofactor for carboxylation enzymes ( add 1 carbon group)
    • Pyruvate carboxylase
    • acetyl-coA carboxylase
    • propionyl-coA carboxylase
  • Deficiency rare
    • dermatitis, alopecia, enteritis
    • caused by antibiotic use or excessive ingestion of raw egg whites

10

Vitamin B9

Folic Acid

  • Converted to tetrahydrofolate (THF)
  • co-factor for 1 carbon transfer/methylation reactions
  • important for synthesis of nitrogenous bases in DNA and RNA
  • Found in leafy green vegetables
  • absorbed in jejunum
  • small reserve pool stored in liver

11

Vitamin B12

Cobalamin

  • Cofactor for homocysteine methyltransferase and methylmalonyl Co-A
  • Found in animal products
  • Very large reserve pool stored in liver
  • Deficiency caused by insufficient intake (vegan, malabsorption, lack of intrinsic factor, gastric bypass or absence of terminal ileum)
  • Deficiency
    • macrocytic, megaloblastic anemia
    • Hypersegmented PMN
    • paresthesia and subacute combined degeneration due to abnormal myelin
    • associated with increased in serum homocysteine and methylmalonic acid levels

12

Vitamin C

  • Anti-oxidant
  • facilitate iron absorption by reducing it to Fe2+ state
  • Necessary for hydroxylation of proline & lysine in collagen synthesis
  • necessary for dopamine B-hydroxylase ( Dopamine--> NE)
  • Found in fruits and vegetables
  • Ancillary treatment for methemoglobinemia by reducing Fe3+ to Fe2+
  • Deficiency
    • Scurvy: swollen gums, Brusing, hemarthrosis, anemia, poor would healing, perifollicular and subperiosteal hemorrhages, corkscrew hair
    • Weakened immune response

13

Vitamin D

D2: Ergocalciferol (plants)

D3: cholecalciferol (milk)

  • formed in sun exposed skin
  • 25 OH D3= storage
  • 1,25 OH D3: active form
  • Function:
    • increase intestinal absorption of calcium and phosphate
    • Increase bone mineralization
  • Deficiency
    • Rickets (child) bone pain and deforminity
    • Osteomalacia in adults
    • Breast fed children should receive oral vitamin D
  • Excess
    • Hypercalcemia
    • Hypercalciuria
    • loss of appetite, stupor
    • seen in sarcoidosis (increase in activation of vitamin D by epithelioid macrophages)

14

Vitamin E

Tocopherol

  • Antioxidant
  • protects erythrocytes and membranes from free radical damage
  • can enhace anti-coagulant effect of warfarin
  • Deficiency
    • Hemolytic anemia
    • acanthocytosis
    • muscle weakness
    • posterior column and spinocerebellar tract demyelination

15

Vitamin K

  • Co-factor for gamm-carboxylation of glutamic acid on proteins required for clotting
    • Factors II, VII, IX, X
    • Protein C & S
    • Wafarin: vitamin K antagonist
  • Deficiency
    • Neonatal hemorrage with increase PT and PTT
    • Can occur after prolonged use of antibiotics
    • Not in breast milk ( neonates are given vitamin K injection at birth)

16

Zinc

  • Essential for activity of many enzymes
    • Zinc finger proteins (transcription factor motifs)
  • Deficiency
    • Delayed wound healing
    • hypogonadism
    • decreased adult hair
    • may predispose to alcoholic cirrhosis

17

Ethanol Metabolism

  • Ethanol --> Acetaldehyde
    • Alcohol Dehydrogenase
    • NAD+
  • Acetaldehyde --> Acetate
    • Acetaldehyde dehydrogenase
    • NAD+
  • NAD+ is the limiting reagent
  • alcohol dehydrogenase= zero order kinetics

Increases NADH/NAD+ levels in liver

  • Pyruvate--> lactate
    • lactic acidosis
  • Oxaloacetate --> malate
    • prevents gluconeogensis 
  • Glyceraldehyde 3 P --> Glycerol-3-P
    • combines with fatty acids to made triglycerides => hepatosteatosis

Increased NADH/NAD+ decreases TCA production of NADH--> increase use of acetyl-coA for ketogenesis

  • Ketoacidosis
  • Lipogeneisis (hepatosteatosis)

Fomepizole: inhibits alcohol dehydrogenase

  • antidote for methanol or ethylene glycol poisoning)

Disulfiram: inhibits acetaldehyde dehydrogenase

  • acetaldehyde accumuates contributing to hangover symptioms

 

 

18

Kwashiorkor

Protein malnutrition

  • results in skin lesions, edema, liver malfuction (fatty change due to decreased apolipoprotein synthesis)

19

Marasmus

Total calorie malnutrition

  • resulting in tissue and muscle wasting
  • loss of subQ fat
  • variable edema

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