Biochemistry Flashcards Preview

Step 1 > Biochemistry > Flashcards

Flashcards in Biochemistry Deck (255)
Loading flashcards...
181

What aa's found in histones?

Positively charged (basic) Arginine and lysine.

182

Glucogenic aa's v. Ketogenic aa's?

Met, Val, His v. Leu, Lys; Ile, Phe, Thr, Trp are both.
VeHeMetly sugary. Kato went to LaLa land.
PITT - best of both worlds.

183

Rate limiting enzyme of urea cycle?

Carbomyl phosphate synthetase I. In mitochondria. CO2 + NH3 + 2ATP -> Carbomyl phosphate. Activated by N-acetylglutamate (formed by enzyme N-acetylglutamate synthetase from acetyl-CoA and glutamate).

184

Urea Cycle?

Carbomyl phosphate + ornithine -(ornithine transcarbamylase)-> citrulline + Asp + ATP -(argininosuccinate synthetase)-> argininosuccinate -(argininosuccinase)-> arginine + (fumarate) -(Arginase)-> Urea + ornithine
Point is to remove ammonia. (Urea gets N from ammonia and aspartate).

185

How does ammonia from muscle get to the liver?

Turned into alanine before transported to liver for transamination into pyruvate + glutamate (->-> urea)

186

AST and ALT do what?

ASP + alpha-ketoglutarate -> oxaloacetate + glutamine; Alanine + alpha-ketoglutarate -> pyruvate + glutamine.

187

Hyperammonemia

Acquired (liver disease) or secondary (urea cycle pblem) - excess free NH4, depleting alpha-ketoglutarate, which stops TCA. Tx = limit protein. Benzoate or phenylbutyrate, which bind aa to excrete. Lactulose to acidify GI and trap NH4+ for excretion. Asterixis, slurring, somnolence.

188

Hereditary hyperammonemias

Ornithine transcarbamylase deficiency - X-linked rec. Mitochondria. Excess carbonyl phosphate -> orotic acid. Inc. orotic acid, dec. BUN, hyperammonemia symptoms. NO megaloblastic anemia unlike orotic acuduria.
CPS-1 deficiency

189

Phenylalanine, Tryptophan, and Histidine make what important compounds?

Phe - Thyroxine, Melanin (tyrosinase), Dopamine (DOPA decarboxylase), NE, Epi; Try - Niacin, NAD, Serotonin, Melatonin; His - Histamine

190

Glycine, Glutamate, Arginine make what important compounds?

Gly - Porphyrin, heme; Glut - GABA, glutathione; Arginine - Creatine, Urea, Nitric oxide

191

Overview of Phenylalanine/Tyrosine catabolism?

Phe -(phenylalanine hydroxylase, BH4)-> Tyr; PKU |_|Tyr -(tyr hydroxylase,BH4)-> DOPA -(DOPA decarboxylase, B6)-> dopamine-(r. VitC)-> NE -(r. SAM)-> Epi -> Metanephrine |_|
Dopamine -> homovanillic acid |_| NE -> Normetanephrine -> vanillylmandelic acid |_| DOPA -(tyrosinase)-> melanin; ALBINISM |_| Tyr ->-> homogentisic acid -(Homogentisate oxidase)-> Maleylacetoacetic acid -> TCA; Alkaptonuria

192

Alkaptonuria

AR. Benign. Deficiency of homogentisate oxidase (tyr -> fumarate pathway). Dark CT, brown sclerae, urine turns black in air. Arthralgias (2/2 cartilage tox of homogentisic acid)

193

Homocystinuria

Homocysteine in urine, ID, osteo, marfinoid, kyphosis, dislocated lens, atherosclerosis -> THROMBOEMBOLISM. Etios include cystathionine synthase deficiency (Cysteine becomes essential AA), homocysteine methyltransferase deficiency, dec. pyridoxal phosphate binding to cystationine synthase. Treatment with B6 helps a lot.

194

Cystinuria

Defect of aa transport (COLA) in renal proximal convoluted tubule leading to hexagonal cystine (=cysteine x2) stones. AR. Dx = cyanide-nitroprusside test. Tx = urinary alkalinization and chelating.

195

Maple Syrup Disease

Normally branched chained aa's (Ile, Leu, Val) converted to alpha-keto acids peripherally via alpha-ketoacid dehydrogenase (B1). Urine smells like syrup. FTT, CNS defects, ID. Tx = restrict ILV (I Love Vermont), and thiamine +keto acid supplementation

196

Glycogen regulation by insulin and glucagon/epi?

Glucagon and epi both eventually act on glycogen phosphorylase kinase, which phosphorylates glycogen phosphorylase. Adenylate cyclase pathway vs. Ca2+; Insulin inhibits glycogen phosphorylase via a phosphatase. And pushes glycogen synthase.

197

Glycogenolysis?

Glycogen phosphorylase removes branch down to 4 residues (Dextrins). 4-alpha-D-glucanotransferase moves 3 glucose-1P's, then alpha-1,6 glucosidase cleaves last one
Cleaves off glucose-1P -(glucose-6-phosphatase)-> Glucose-6-P

198

Glycogenesis?

Glucose 1-P -(UDP-glucose pyrophosphorylase)-> UDP-glucose -(glycogen synthase)-> glycogen;
Links are alpha-1,4 while branches are alpha-1,6

199

Glycogen storage disease (four of them)

Very Poor Carbohydrate Metabolism: Von Gierke (most common), Pompe, Cori, McArdle (V)

200

Von Gierke disease (type I)

Glucose-6-phosphatase; Severe fasting hypoglycemia. Lactate high, glycogen high, hepatomegaly. Cells can't remove phosphate off of glucose-6P; AR. Tx = freq. oral glucose; avoid fructose and galactose.

201

Pompe disease (II)

LYSOSOMAL alpha-1,4-glucosidase (small amount of glycogen degraded via this method). Cardiomyopathy. AR. LYSE his head, he's so pompous.

202

Cori disease (III)

Alpha-1,6,glucosidase (last debranch). AR. Gluconeogenesis okay. Mild von Gierke.

203

McArdle disease (IV)

Skeletal muscle glycogen phosphorylase. AR. Increased Glycogen in MUSCLE but CAN'T break down-> cramps, MYOglobinuria with exercise, arrhythmias, weakness.

204

Fabry Disease

alpha-galactosidase A. Ceramide trihexoside. XR. Peripheral neuropathy, angiokeratomas, cardio/renal. AGA - American GI association, cuz Dr. Fabry was a dermatologist.

205

Gaucher disease

Glucocerebrosidase (B-glucosidase). Glucocerebroside. AR. Hepatosplenomegaly, pancytopenia, GAUCHER cells (lipid-laden macrophages!). Recombinant glucocerebrosidase available tx. Gaucher is a Cerebral!

206

Tay-Sachs disease

Hexosaminidase A. GM2 ganglioside. AR. CHERRY-Red spot on macula. No hepatosplenomegaly. A HEX on the people.

207

Krabbe disease

Galactocerebrosidase. Most Cerebral of the Galactosy. AR. Peripheral neuropathy, dvpt delay.

208

Metachromatic leukodystrophy

Arylsulfatase. Central and peripheral demyelination with ataxia, dementia. Many-colored Arya faces sulfur pits.

209

Hurler syndrome

alpha-L-iduronidase. AR. Heparan sulfate. Dvpt delay, gargoylism, airway, corneal. iDuron duran is a hurler.

210

Hunter syndrome

iduronate sulfatase. X-linked recessive. Mild hurler + aggressive. Hunter sounds more sophisticated than hurler right?