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Metabolism Random Flashcards

1
Q

Disulfiram

A

inhibits ALDH (acetaldehyde dehydrogenase): this will cause buildup of acetaldehyde which causes the Sx of EtOH hangovers

used to discourage drinking

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2
Q

Fomepizole

A

inhibits ADH (alcohol dehydrogenase)

used as antidote For Overdoses of Methanol or Ethylene glycol

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3
Q

Ethanol metabolism pathway

A

Ethanol -> acetaldehyde (ADH) in cytosol -> acetate (ALDH) in mitochondria

Uses up a lot of NAD+ so you end up with a lot of NADH around

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4
Q

CYP2E1

A

used as overflow pathway when the regular ethanol metabolism system is overloaded in the MICROSOME

this enzyme also metabolizes a lot of other drugs (ex. Tylenol)

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5
Q

Consequences of ethanol metabolism

A
  1. increased NADH/NAD+ ratio
  2. energy depletion: TCA cycle is blocked, increased lactic acidosis
  3. Hypoglycemia: gluconeo. and glycolysis are blocked
  4. increased acetyl coA: FA synthesis accelerated, ketoacidosis
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6
Q

Rate limiting enzyme in glycolysis

A

PFK-1

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7
Q

Hexokinase vs. Glucokinase: location, Km, Vmax

A

Glucokinase: located in liver and beta cells of pancreas, has HIGH Km aka LOW affinity, has a HIGH Vmax aka works quickly

Hexokinase: located in most tissues except liver and beta cells of pancreas, has LOW Km aka HIGH affinity, has a LOW Vmax aka slower

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8
Q

End products of glycolysis

A

2 Pyruvate, 2 NADH, 2 ATP (4 total but 2 consumed)

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9
Q

Rate limiting enzyme for gluconeogenesis

A

Fructose 1,6 bisphosphatase

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10
Q

Pyruvate dehydrogenase complex function and cofactors

A

Links glycolysis and the TCA cycle

Requires TLC for Nancy:
Thiamine (B1)
Lipoic acid
CoA (B5)
FAD (B2)
NAD (B3)

Is activated when it is dephosphorylated by PDH phosphatase (ie during exercise)

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11
Q

Pyruvate dehydrogenase deficiency

A

Buildup of pyruvate that is shunted to lactate (via LDH) and alanine (via ALT)
X linked disorder
Lactic acidosis
Increase in serum alanine starting in infancy

Tx: increase ketogenic nutrients (fat, lysine, leucine)

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12
Q

HMP shunt purpose

A

provides a source of NADPH from glucose-6P
NADPH is required for glutathione reduction inside RBCs, fatty acid and cholesterol biosynth
Provides source of ribose (nucleotide synthesis; glycolytic intermediates
No ATP used OR produced

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13
Q

HMP reactions (oxidative and nonoxidative)

A

Oxidative is irreversible, uses G6PD, and produces NADPH

Non oxidative is reversible, uses transkelotases and phosphopentose isomerase, requires B1, and produces G3P and ribose

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14
Q

G6PD deficiency

A

X linked recessive
NADPH needed for glutathione reduction
Glutathione detoxifies free radicals in RBCs
Hemolytic anemia bc of poor RBC defense against oxidizing agents

Oxidizing agents: fava beans, sulfonamides, primaquine, antiTB drugs
Infection can ppt hemolysis bc inflamm response produces free radicals–>oxidative damage

Peripheral smear: heinz bodies (denatured Hb ppts within RBC), bite cells (phagocytic removal of heinz bodies by splenic macrophages)

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15
Q

Fructose metabolism pathway

A

Fructose–(fructokinase–>fructose 1 P–(adolase B)–>…met continues…

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16
Q

Essential fructosuria

A

Autosomal recessive
Defect in fructokinase
Benign, asymptomatic bc fructose is not trapped in cells
Fructose in blood and urine

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17
Q

Fructose intolerance

A

Autosomal recessive
Deficiency in adolase B
Fructose 1 P accumulates–>decrease in available phosphate–>inhibition of glycolysis and gluconeogenesis
Symptoms after consumption of fruit, juice, honey
Negative urine dipstick (tests for glucose only)
Reducing sugar can be detected in urine

Symptoms: hypoglycemia, jaundice, cirrhosis, vomiting

Tx: decrease fructose and sucrose intake

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18
Q

Galactose metabolism pathway

A

Galactose can either go:
Galactose–(galactokinase)–>galactose 1 P–(uridyltransferase)–>glucose 1 P–>glycolysis

OR

galactose –(aldose reductase)–>galactitol

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19
Q

Galactokinase deficiency

A

Galacitol accumulates if galactose is present in diet
Mild
Symptoms begin when infant breast/formula feeds
Galactosemia, galactosuria, infantile cataracts

Infant may have failure to track objects or to develop a social smile

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20
Q

Classic galactosemia

A

Severe
Absence of galactose-1-phosphate uridyltransferase
Aut recess
Damage due to accumulation of galacitol, which accum in the lens of the eye, and P depletion
Failure to thrive, jaundice, hepatomeg, cataracts, intellect disability
Can –> e coli sepsis in neonates

Tx: exclude galactose and lactose from diet

FAB GUT pneumonic:
fructose adolase B, galactose to uridyltransferase

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21
Q

Sorbitol

A

Alcohol counterpart of glucose

glucose–(aldose reductase)–>sorbitol–(sorbitol dehydrogenase)–>fructose

Traps glucose in the cell; tissues that do not have sorbitol dehydrogenase get intracell sorbitol accumulation
Schwann cells, retina, kidney, and lens (mostly) only have aldose reductase
–>cataracts, retinopathy, peripheral neuropathy
problem in chronic hyperglycemia DM pts

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22
Q

Lactase function and deficiency

A

–>dietary lactose intolerance
lactase functions on brush border to digest lactose–>glucose + galactose

Primary due to age dependent decline after childhood
Secondary due to losh of brush border (gastrienteritis from rotavirus, autoimmune)

Congenital deficiency is rare

Findings: bloating, cramps, flatulence, osmotic diarrhea

23
Q

Urea cycle function and important players

A

Nitrogen excretion; occurs in liver

Part in mitochondria, part in cytoplasm

Carbamoyl phosphate synthetase I is RLS; it requires N-acetylglutamate as an allosteric activator

Ornithine transcarbamylase converts ornithine–>citruline

Disorders–>hyperammonemia (confusion, vomiting, tachypnea)

24
Q

Cahill and Cori cycle

A

Transport ammonia between muscle and liver; uses alanine and glutamate
Uses alphaketoglutarate

25
Hyperammonemia
Acquired (liver disease) or inherted Excess NH3-->depletes alphaketoglutarate-->inhibition of TCA cycle Tx with limited protein diet Tremor, slurring of speech, vomiting, cerebral edema, blurred vision Meds that lower ammonia levels: lactulose (acidifies GI tract-->NH4 excreted) Rifaximin (decreases ammoniagenic bacteria) Benzoate, phenylacetate, phenylbutyrate (binds to NH4-->excretion)
26
N-acetylglutamate synthase deficiency
Autosomal recessive Required cofactor for CPS1 Hyperammonemia Neonates: poorly regulated resp and body temp, poor feeding, developmental delay, intellect disability (same as CPS1 deficiency)
27
Ornithine transcarbamylase deficiency
X linked recessive most common urea cycle disorder excess carbamoyl phosphate is converted to orotic acid (part of pyrimidine synthesis pathway) Findings: increased orotic acid in blood and urine, low BUN, hyperammonemia, No megaloblastic anemia (vs orotic aciduria, which is when there is low pyrimidine synthesis bc of megaloblastic anemia-->orotic acid accumulation)
28
Phenylketonuria - what's the etiology?
deficient phenylalanine hydroxylase or BH4 cofactor
29
Phenylketonuria - what is the treatment?
Avoid phenylalanine (found in aspartame) and supplement tyrosine (becomes essential) and/or BH4 supplementation (depends on etiology)
30
Phenylketonuria - symptoms/presentation
Musty Crusty: musty body odor, eczema intellectual disability, growth delay, seizures fair skin & eczema *musty body odor (specifically sweat and urine)* albinism (tyrosine needed to make melanin) excretion of phenylketones in urine (causes smell) Babies are all screened on day 2/3 of life
31
What can happen to a pregnant woman with PKU?
If she is not keeping her PKU under control (following diet), the excess phenylalanine is teratogenic specifically to CNS development --> microcephaly, intellectual disability, growth retardation, congenital heart defects
32
Phenylketonuria - inheritance
Autosomal recessive (enzyme deficiency)
33
Maple syrup urine disease - etiology/pathogenesis
Deficient branched chain alpha ketoacid dehydrogenase (uses B1 as cofactor) - can't degrade branched AA (Iso, Leu, Val)
34
Maple syrup urine disease - inheritance
Autosomal recessive (enzyme deficiency)
35
Maple syrup urine disease - sx/presentation
Urine that smells like maple syrup (duh!), vomiting, poor feeding - present in days 4-7 of life Eventually --> CNS defects, intellectual disability, death (*Leucine crosses BBB and is responsible for the CNS effects)
36
Maple syrup urine disease - treatment
Avoid branched AAs in diet (Iso, Leu, Val) and supplement thiamine
37
Alkaptonuria - etiology/pathogenesis
Deficiency of homogentisate oxidase (tyrosine --> fumarate)
38
Alkaptonuria - inheritance
autosomal recessive (enzyme deficiency)
39
Alkaptonuria - symptoms/presentation
Blue-black coloration of cartilage (called ochronosis): connective tissue, ears, sclerae (brown pigment) Urine will turn black when left out for a bit Debilitating arthralgias, ankylosis, arthritis (toxic to cartilage) *All due to effects of homogentisate build-up
40
Cofactors of branched-chain alpha-ketoacid dehydrogenase
5: TPP, lipoic acid, CoA, NADH, FADH2
41
Homocystinuria - etiology
3 types: cystathione synthase deficiency decreased affinity of cys synthase for B6 cofactor methionine synthase deficiency *All 3 lead to homocysteine build-up.
42
Homocystinuria - inheritance
All 3 types are autosomal recessive (enzyme deficiencies).
43
What reactions do cystathione synthase and methionine synthase catalyze?
CS: homocysteine + Ser --> Cystathione (*requires B6) MS: Homocysteine --> Methionine (*req B9 + B12)
44
Homocystinuria - treatment(s)
CS deficiency: Cys, B9, B6, B12 supplementation + reduced methionine consumption CS decreased affinity for B6: Cys + B6 supplementation MS deficiency: supplement Methionine
45
Homocystinuria - sx/presentation
Marfanoid habitus but with down and in lens dislocation (Marfan's is up and out) Intellectual disability
46
Cystinuria - etiology
Autosomal recessive deficiency of renal transporter (in PCT) for COLA: cysteine, ornithine, lysine, arginine
47
Cystinuria - diagnostic test
Positive sodium cyanice-nitroprusside test: | Cyanide converts cystine to cysteine, cysteine binds nitroprusside, turning the solution purple.
48
Cystinuria - sx/presentation
Typically presents as renal kidney stones in a child, possibly as staghorn calculi. Stones are radiolucent on XR Crystals are hexagonal
49
Cystinuria - treatment
To prevent kidney stones: alkalinization of urine (acetazolamide) and hydration/low salt diet are 1st line chelation (penicillamine) if necessary
50
Rate limiting enzyme glycogenesis
glycogen synthase
51
Rate limiting enzyme glycogenolysis
glycogen phosphorylase
52
Arsenic poisoning: how does it present? why is it important for metabolism?
Inhibits lipoic acid in pyruvate dehydrogenase complex Presents as garlic breath with GI Sx (vomiting, rice water stools), QT prolongation
53
End products of TCA cycle
3 NADH, 1 FADH2, 2 CO2, 1 GTP per acetyl CoA mc 10 ATP per acetyl CoA 20 ATP per glucose mc

STEP1 (11 decks)

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