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FA BCH > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Benign appearance of fructose in blood and urine. Name enzyme deficiency and disease?

A

Essential Fructosuria

Fructokinase

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2
Q

Symptoms after consuming fruit, juice, honey. Hypoglycemia, jaundice, cirrhosis + vomiting

A

Fructose Intolerance
Def Aldolase B
-Fructose-1 phosphate accumulates, decreases phosphate available for gluconeogensis + glycogenolysis

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3
Q

Infantile cataracts, possible failure to track objects or to develop a smile. Disease, enzyme, what accumulates

A

Galactokinase deficiency

Galactitol accumulates - relatively mild

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4
Q

FTT, jaundice, HM, infantile cataracts, intellectual disability, possible E coli sepsis in neonates. Disease, enzyme, treatment

A

Classic Galactosemia
Absent galactose-1-phosphate uridyltransferase – galactitol accumulates (esp in lens of eye)
Tx: exclude galactose and lactose (glucose + galactose)

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5
Q

Enzyme that converts glucose to sorbitol

Location with primarily this enzyme

A

Aldose reductase

The lens

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6
Q

Enzyme that converts sorbitol to fructose

A

Sorbitol dehydrogenase

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7
Q

Dx lactase deficiency

A

Decrease stool pH

Inc breath Hydrogen content

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8
Q

Hyperammonemia in neonate, poorly regulated respiration and body temp. Poor feeding, dev delay, intellectual disability. Def? Cofactor for what?

A

N-acetylglutamate synthase deficiency

Required cofactor for CPS-1 (mitochondria, urea cycle)

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9
Q

Elevated orotic acid in blood and urine, dec BUN, syx of hyperammonemia. First few days of life, or can be later. No megaloblastic anemia. Enzyme, inheritance, and ddx

A

Ornithine transcarbamylase deficiency (most common urea cycle disorder)
X-linked recessive
Body can’t eliminate NH4, converts excess carbamoyl phosphate to orotic acid
Ddx: Orotic Aciduria (pyrimidine synthesis, has megaloblastic anemia)

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10
Q

Intellectual disability, growth retardation, seizures, fair skin, eczema, musty body odor. Enzyme (2), what becomes essential, dx, tx

A

PKU
Def in phenylalanine hydroxylase OR its cofactor BH4 (tetrahydrobiopterin)
Tyrosine becomes essential
Dx w/ clinical picture + excess phenylalanine leads to increase phenylketones in urine (phenylacetate, phenyllacetate, phenylpyruvate)
Tx: avoid phenylalanine (in aspartame), increase tyrosine + BH4 supplementation

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11
Q

Severe CNS defects, intellectual disability, and death. Urine with maply syrup/burnt sugar smell. Enzyme + dx + tx

A

Maple Syrup Urine Disease
Dec alpha-ketoacid dehydrogenase (B1) – cant break down branched amino acids (Isoleucine, Leucine, Valine)
Inc alpha-ketoacids in blood (esp leucine)
Tx: restrict these AA in diet, give thiamine

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12
Q

Dark connective tissue, brown pigmented sclera, urine turns black w/ prolonged air exposure to air. Name, enzyme, pathway, possible complication

A

Alkaptonuria (Ohchronosis)
Homogentisate Oxidase (degrades tyrosine to fumarate)
Accumulate homogentisic acid in tissues (pigment forming)
Can have debilitating arthralgias - homogentisic acid toxic to cartilage

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13
Q

Ethanol Metabolism
______ to ______ to ______
2 enzymes

A

Ethanol → Acetylaldehyde → Acetate

  1. Alcohol Dehydrogenase (cytosol)
  2. Acetylaldehyde Dehydrogense (mito)
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14
Q

Fomepizole MOA, Use

A

Blocks alcohol dehydrogenase

Use w/ ethelyene glycocol or methanol poisoning

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15
Q

Disulfram MOA, Use

A

Blocks acetylaldehyde dehydrogenase (accumulate acetylaldehyde)
To discourage alcoholics from relapsing

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16
Q

Ethanol metabolism kinetics?

A

Zero-order (constant amount per unit time)

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17
Q

Limiting reagant for EtOH metabolism?

A

NAD+

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18
Q

Ethanol metabolism effects on other pathways (3)

A
  1. pyruvate → lactate (lactic acidosis)
  2. oxaloacetate → malate (can’t do gluconeogenesis → fasting hypoglycemia)
  3. dihydroxyacetone → glycerol-3-phosphate (combines w/ fatty acids and makes TGs – fatty liver, hepatosteatosis)
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19
Q

Chronic EtOH disfavors what type of metabolism, and favors what?

A

High NADPH/NAD+ ratio disfavors TCA (and production of NADPH)
-favors use of acetyl-CoA for ketogenesis + lipogenesis

20
Q

Function of Pyruvate Dehydrogenase Complex? What stimulates it?

A 
Mitochondrial enzymes complex, links glycolysis + TCA 
Stimulated by exercise 
1. Inc NAD+/NADH ratio
2. inc ADP
3. inc Ca2+
21
Q

Required Enzymes and cofactors for PD complex?

A

TLC for No Body

  1. thiamine (B1) + pyrophosphate
  2. Lipoic acid
  3. CoA (B5 - pantothenic acid)
  4. NAD+ (niacin, B3)
  5. FAD+ (riboflavin, B2)
22
Q

Formula of PD complex

A

Pyruvate + NAD+ + CoA → acetyl-CoA + CO2 + NADH

23
Q

What other complex requires TLC for No Body?

A

alpha-ketoglutarate dehydrogenase

- converts alpha ketoglutarate to succinyl-CoA (TCA cycle)

24
Q

MOA of arsenic? Clinical presentation

A

Arsenic inhibits lipic acid

s/s: vomiting, rice water stools + garlic breath

25
Q

Neuro defects, lactic acidosis, increased serum alanine in infancy? Disease, mechanism, tx

A

Pyruvate Dehydrogenase Deficiency
Build up of pyruvate, shunted to lactate (LDH) and alanine (ALT)
Tx: inc ketogenic nutrients (high fat + onLy pureLy ketogenic amino acids → Lysine + Leucine)

26
Q

4 fates of pyruvate

A
  1. alanine (via ALT + B6): amino acids from muscle to liver
  2. acetyl-CoA (via pyruvate dehydrogenase w/ TLC,NB): glycolysis to TCA
  3. oxaloacetate (via pyruvate carboxylase w/ Biotin): can replenish TCA or be used in gluconeogenesis
  4. lactic acid (via lactic acid dehydrogenase w/ B3) - end of anaerobic glycolysis (+ Cori Cycle)
27
Q

What does the urea cycle do?

A

converts excess nitrogen (NH3) from amino acid catabolism to urea → excretion by kidneys

28
Q

What other pathways are affected by hyperammoniunemia?

A

excess NH4+ depletes alpha-ketoglutarate

inhibits TCA cycle

29
Q

4 ways to treat hyperammonemia

A
  1. Dec protein in diet
  2. Lactulose: acidifies GI tract, traps NH4+
  3. Rifaximin: dec NH4+ making bacteria in gut
  4. Benzoate or Phenylbutyrate: bind amino acids and increase excretion
30
Q

When to screen for PKU and why

A

2-3 days after birth, bc will be normal first few days due to mom’s enzymes

31
Q

Maternal PKU findings in infant

A

microcephaly, intellectual delay, congenital heart defects, and growth retardation

32
Q

Intellectual disability, osteoporosis, marfanoid habitus and inc homocysteine in urine

A

Homocystinuria

33
Q

Complications of homocystinuria

A 
osteoporosis
kyphosis
marfanoid habitus
down and in lens subluxation
thrombosis
atherosclerosis
34
Q

3 causes of homocysteinuria

A
  1. cystathione synthase deficiency
  2. decreased affinity of cystathione synthase for cofactor (B6- pryidoxal phosphate)
  3. homocysteine methyltransferase def (aka methionine synthase)
35
Q

Tx Cystathionine Def

A
  1. Dec methionine
  2. Inc Cysteine and B12 and folate in diet
    * *push pathway away from deficienct enzyme
36
Q

Tx affinity problem w/ cystathione + B6

A

Lots of B6 and cysteine in diet

37
Q

Tx methionine synthase def (and other name for enzyme)

A

methionine synthase aka homocysteine methyltransferase

tx: inc methionine in diet

38
Q

What’s defective in cystinuria?

What occurs?

A

defective amino acid transporter in distal PCT and intestine

Excess cystine in urine → preciptates urinary cystine stones (hexagonal)

39
Q

amino acids missing in cystinuria

A 
COLA - can't reabsorb
Cysteine
Ornithine
Lysine
Arginine
40
Q

How to dx cystinuria

A

urinary cyanide-nitroprusside test

41
Q

what is cystine?

A

2 cysteines connected w/ di-sulfide bond

42
Q

How to tx cystinuria (big picture and 2 ways)

A

Dec solubility of stones, good hydration

  1. alkinize urine (potassium CITRATE or Acetazolamide)
  2. Chelating agents (penicillamine)
43
Q

hypochromic megaloblastic anemia, neuro syx, growth retardation, high levels of orotic acid in urine

A

Orotic Aciduria

44
Q

Cause of orotic aciduria?

A

problem with pyrimidine synthesis

1. orotate phosphoribosyl transferase and OMP decarboxylase

45
Q

Tx oritic aciduria

A

Uridine supplementation

-converted to UMP and inhibits CPS-II

FA BCH (5 decks)

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