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Step 1 (Let's Do This)! > Biochem > Flashcards

Biochem Flashcards

1
Q

Function of Vit. A (retinol)?

A
  • Antioxidant
  • visual pigment component (retinal)
  • squamous epithelial cell differentiation into specialized cells (i.e. pancreas, mucus-secreting)
  • prevents squamous metaplasia
  • Tx: measles, & AML-M3
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2
Q

S/E of Vit A deficiency?

A
  • Night blindness

- Dry skin

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3
Q

What is is Vit A used for in treatment?

A

Wrinkles, acne
Measles
AML-M3 subtype

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4
Q

Excess Vitamin A can cause hat Sx?

A
  • Arthralgias
  • fatigue, headache, sore throat
  • skin changes
  • alopecia
  • Teratogenic
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5
Q

Why is Vit A based drugs not given to women? Give example of drug and requirements before admin

A
  • Teratogenic: cleft palate & cardiac abnormalities
  • Retinol an act on embryogenesis. Part of Hox gene. If excess, Hox gene becomes dys-Fx
  • before Isotretinoin (severe acne), requires neg pregnancy test and reliable contraception
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6
Q

What tissues are effected first by Thiamine deficiency? What Tx can worsen Sx?

A

Brain and CNS; heart (highly Aerobic)
Vitamin B1 needed for ATP production.
Glucose infusion worsens

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7
Q

What enzymes require Thiamine? In what form does it act?

A
  • Thiamine is a cofactor for enzymes as TPP: Thiamine pyrophosphate. Used for decarboxylation:
    1) Pyruvate Dehydrogenase (Glcolysis –> TCA)
    2) α-ketoglutarate dehydrogenase (TCA)
    3) Transketolase (HMP)
    4) Branched chain amino acid dehydrogenase
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8
Q

Deficiency of what enzyme can cause buildup branch chain amino acids? What is the disease and Sx?
Describe in detail

A

Maple Syrup Urine Disease [AR]
Decrease in α-ketoacid dehydrogenase. Deficiency causes buildup of α-ketoacids: Ile, Leu, Val.
Sx: Severe CNS defets, mental retardation, death.
“I Love Vermont maple syrup from maple trees w/ branches

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9
Q

What are causes of Homocystinuria?

A

Defect [AR] in

  • Cystathionine synthase,
  • N5-methyl THF homocysteine methyltransferase (NPTHM)
  • or decreased affinity of CS for Vit. B6 (cofactor)
  • B12 def another cause, needed for NPTHM
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10
Q

Homocysteinuria affects whih enzyme pathway?

A

Homocysteine –(NPTHM)-> Methionine

Homocysteine–(CS & B6)–> Cystathionine –(B6)->Cysteine

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11
Q

Explain Sx of Homocystinuria

A

Homocysteine toxic to
-vascular endothelium: CAD, ↑PLTadhesion→Thromboembolis, stroke, MI
-MR
-Interferes w/ collaen formation: osteoporosis, lens dislocation (ectopia lentis).
Tall height, Arachnodactyly, elongated limbs, scoliosis, aka “Marfanoid habitus”.
DON’T CONFUSE W/ MARFAN SYNDROME!

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12
Q

How to Tx Homocystinuria?

A
  • Decrease methionine in diet

- increase cysteine, folate, B12, & high dose Vit B6 in diet.

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13
Q

What causes Hartnup disease?

A

Mutation [AR] in neutral amino acid transporter in renal PT & small intestine epithelial cells.
Deficiency in neural AA, like Tryptophan

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14
Q

Sx of Hartnup disease

A

↓Tryptophan → Niacin deficiency.

  • Pellegra (3 Ds)
  • photosensitive dermatitis (face, neck, limbs),
  • Neuro: personality disturbance, cerebellar ataxia, MR
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15
Q

Tx of Hartnup disease?

A

Nicotinic acid supplements

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16
Q

Lab findings of Hartnup

A

Renal aminoaciduria in urine

17
Q

Lab findings of Homocystinuria

A

↑Methionine in serum

↑↑homocysteine in urine

18
Q

What causes Cystinuria?

Tx?

A

Defect [AR] in renal PCT and intestinal absorption of Cysteine, Ornithine, Lysine, &Arginine
“Kidneys don’t drink COLA”

Tx: drink water, & alkalize urine

19
Q

Sx and lab findings of Cystinuria

A
  • cysteine kidney stones (CT radiograph shows)
  • hematuria and cystine hexagonal crystals when urine cools
  • Staghorn calculi
  • Urine AA chromatography: COLA
20
Q

What diseases seen w/ Thiamine deficiency?

A

-Wernicke Korsakoff: classic triad of confusion, ophthalmoplegia, & ataxia.
+ confabulation, personality change, memory loss (permanent)
-Dry Beri Beri (CNS): polyneuritis, symmetrical muscle wasting
-Wet Beri Beri (heart):dilated cardiomyopathy, edema

21
Q

What CNS tissues affected by B1 deficiency?

A

Mamillary bodies

Medial Dorsal Nucleus of thalamus

22
Q

What is function for Vit B2?

A

Vit Riboflavin

-cofactor Redox (i.e. FADH2). FAD & FMN derived from riboFlavin (B2 = 2 ATP)

23
Q

Sx of Vitamin B2 deficiency

A

-Cheilosis (lip inflammation, scaling fissures at corners of mouth)
-Corneal vascularization
-Magenta colored tongue
“The 2 C’s of B2”

24
Q

Function of Vit B3?

Derived from what?

A

Part of NAD+, NADP+. Used in redox rxns.

Derived from tryptophan (tryptophan converted to Niacin w/ Vit B6)

25
Q

Vit B3 defiiency

A
  • Glossitis

- Pellagra: Diarrhea, Dementia, Dermatits

26
Q

What diseases and drugs can cause Vitamin B3 deficiency? Cause in elderly?

A
  • Malignant Carcinoid syndrome (↑tryptophan metabolism)
  • Isoniazid: ↓B6
  • Hartnup Disease
  • “tea and toast” diet in elderly
27
Q

Vitamin Niacin excess cause

A
  • Facial flushing (due to Rx for hyperlipidemia) by vasodilation
  • high doss Niacin can reduce LDL, VLDL, & ↑HDL
28
Q

What is Vitamin B5?

What is its function?

A

Pantothenate

Part of CoA (cofactor for acyl transferas), FA synthase (Acetyl CoA)

29
Q

What are Sx of B5 deficiency?

A
  • Dermatitis
  • Enteritis
  • Alopecia
  • Adrenal insufficiency
  • Paresthesias- pin’s & needles
  • Dysesthesias- act of touching a part of the body causes some unpleasant sensation, such as pain, burning, or tingling.
30
Q

Function of Vitamin B6?

A 
Converted to Pyridoxal phosphate, a cofactor for transamination (original AA → α-ketoacid), decarboxylation rxns, glycogen phosphorylase.
Synthesis of:
-Cystathionine
-Heme
-Niacin
-Histamine
-Neurotransmitters: Epi, NE, 5-HT, GABA
31
Q

MCC of B6 deficiency and Sx

A

Isoniazid Tx, oral contraceptive, and Alcoholism.

Sx: Convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemia

Step 1 (Let's Do This)! (10 decks)

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