metabolism

Question 1

homogentisate oxidase deficiency

Answer 1

alkaptonuria

benign disorder of tyrosine metabolism (blocks metabolism of phenylalanine and tyrosine at the level of homogentisic acid–> prevents conversion of tyrosine to fumarate)

pigment forming homogentisic acid accumulates in tissue

Question 2

what is diminished in hyperammonemia of hepatic encephalopathy or urea cycle enzyme deficiencies?

Answer 2

alpha ketoglutarate and glutamate (glutamine is high)

Question 3

B12 deficiency

Answer 3

can lead to a folate trap–> impaired synthesis of methionine and sometimes homocysteinuria (because reaction pushed in the other direction)

Question 4

G6PD deficiency

Answer 4

cant complete HMP shunt, so decreased NADPH concentration; decreased NADPH in RBCs–> decreased glutathione reduction–> less detoxification of free radicals and peroxides–> hemolytic anemia

Question 5

galactose-1-phosphate uridyltransferase deficiency

Answer 5

classic galactosemia; damaged caused by accumulation of toxic substances (not just galacitol)

Question 6

HGPRT deficiency?

Answer 6

defective purine salvage

Question 7

medium chain acyl-CoA dehydrogenase deficiency

Answer 7

disorder of fatty acid oxidation –> cant break down fatty acids into acetyl-CoA–> accumulation of 8-10 carbon fatty acyl carnitines in the blood and hypoketotic hypoglycemia

Question 8

fructokinase deficiency

Answer 8

essential fructosuria

ALTERNATE METABOLIC PATHWAY: increase of fructose-6-phosphate (via hexokinase activity)–> metabolized in glycolytic pathway or converted to G6P

Question 9

lipoprotein lipase deficiency

Answer 9

familial dyslipidemia type I- hyperchylomicronemia

increased chylomicrons, triglycerides, cholesterol

Question 10

LDL receptor deficiency or defect

Answer 10

familial dyslipidemia type IIa- family hypercholesterolemia

increased LDL, cholesterol

Question 11

hepatic overproduction of VLDL

Answer 11

familial dyslipidemia type IV- hypetriglyceridemia

increasedV LDL, triglycerides

Question 12

aldolase B deficiency

Answer 12

fructose intolerance

increased concentration of fructose-1-phosphate–> decreased available phosphate and inhibition of glycogenolysis and gluconeogenesis; sxs after consuming fruit, juice or honey

Question 13

galactokinase deficiency

Answer 13

galacitol accumulates in the blood if galactose is present; mild condition

Question 14

cystathione synthase deficiency

Answer 14

homocystinuria

Question 15

decreased cystathionine synthase affinity for pyridoxal phosphate

Answer 15

homocystinuria

Question 16

homocysteine methyltransferase deficiency

Answer 16

homocystinuria

Question 17

systemic primary carnitine deficiency

Answer 17

inherited defect in transport of long-chain fatty acids into the mitochondria–> toxic accumulation

Question 18

alpha-ketoacid dehydrogenase

Answer 18

MSUD

blocked degradation of branched amino acids (isoleucine, leucine, valine)

Question 19

deficiency

Answer 19

pathophys

Question 20

phenylalanine hydroxylase deficiency

Answer 20

PKU

excess phenylalanine–> excess phenylketones in urine

Question 21

PDH complex deficiency?

Answer 21

pyruvate can’t enter glycolysis/TCA cycle so is converted to lactate and alanine instead

Question 22

n-acetylglutamate synthase deficiency

Answer 22

required cofactor for carbamoyl phosphate synthetase I–> can’t do urea cycle–> hyperammonemia