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Flashcards in Biochemistry Deck (293)
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211

Pyruvate dehydrogenase complex: what are the 5 cofactors needed for the 3 enzymes in the complex?

"Tender Loving Care For No one"
1) Thiamine/TPP/B1/Pyrophosphate
2) Liopoic acid
3) CoA (B5;Pantothenate)
4) FAD (B2, riboflavin)
5) NAD (B3, niacin)

***note: same cofactors are used in the alpha-ketoglutarate dehydrogenase complex, in the TCA cycle (alpha-ketoglutarate --> succinyl CoA)

212

Pyruvate dehydrogenase deficiency: what's the treatment?

get lactic acidosis, d/t backup of substrate (pyruvate and alanine)
-treat by intake of ketogenic nutrients: high fat content or lysine and leucine (the only purely ketogenic AA's)

213

What are the 4 fates of pyruvate?

1) Acetyl CoA (enters TCA cycle)
2) Oxaloacetate (replenish TCA cycle, or converted to PEP and used in gluconeogenesis)
3) Lactate (end of anaerobic glycolys: pthwy for RBCs, leukocytes, kidney medulla, lens, testes, cornea)
4) Alanine (carries amino groups to liver from muscle)

214

5 cofactors required for the alpha-ketoglutarate dehydrogenase complex (in the TCA cycle)?

same as for the Pyruvated Dehydrogenase complex!:
-B1
-B2
-B3
-B5
-Lipoic acid

(or, "Tender Loving Care For No one": Thiamine=B1, Lipoic Acid, CoA =B5, FAD =B2, NAD=B3)

215

Electron transport chain: NADH and FADH2 yield how many ATP?

1 NADH --> 3 ATP
1 FADH2 --> 2 ATP

216

In what organ does gluconeogenesis mainly occur?

mostly in liver (also in kidney, intestinal epithelium)

217

Heinz bodies

oxidized hemoglobin precipitated within RBCs; seen in G6PD deficiency

218

Bite cells

result from phagocytic removal of Heinz bodies by splenic macrophages; seen in G6PD deficiency

219

defect in fructokinase

-essential fructosuria
-autosomal recessive
-mild/asymptomatic disease, because fructose doesn't enter cells
-fructose in blood and urine

220

Aldolase B deficiency

-Fructose intolerance
-autosomal recessive
-get accumulation of Fructose-1-Phosphate, so decreased Phosphate availability --> inhibits glycogenolysis and gluconeogenesis
-symptoms: hypoglycemia, jaundice, cirrhosis, vomiting
- treat by decreasing intake of fructose and sucrose

221

Galactokinase deficiency

-mild autosomal recessive disease; get galactose in blood and urine
-infants may have infantile cataracts, and may fail to track objects or develop a social smile

222

absence of Galactose-1-phosphate uridyltransferase

-classic galactosemia
-autosomal recessive
-galactitol accumulates, and may deposit in lens of eyes
-symptoms: FTT, jaundice, hepatomegaly, infantile cataracts; MR; also: pts can't tolerate milk early in life! (b/c lactose = galactose + glucose)
-treat by excluding galactose and lactose from diet

223

infantile cataracts? think:

galactokinase deficiency or classic galactosemia

224

Aldolase reductase

converts glucose to sorbitol.
*some tissues can go on to convert the sorbitol to fructose, via sorbitol dehydrogenase (in liver, ovaries, seminal vesicles)
*other tissues (schwann cells, lens, retina, kidneys) only have aldose reductase, so sorbitol gets trapped in cells --> osmotic damage (ie cataracts, retinopathy, peripheral neuropathy seen in diabetic patients with chronic hyperglycemia)

225

List the essential AAs:

"PVT TIM HALL" = Phe, Val, Thr, Trp, Ile, Met, His, Arg, Leu, Lys

*glucogenic: met, val, arg, his
*glucogenic/ketogenic: ile, phe, thr, trp
*ketogenic: leu, lys

226

which 2 amino acids are required during periods of growth (so many be found in body building supplements)?

Arg and His

227

Lactulose

sweet syrup that can't be digested; used as treatment for hyperammonemia: acidifies the GI and traps NH4+ for excretion

228

orotic acid in blood/urine, decreased BUN, symptoms of hyperammonemia

Ornithine transcarbamoylase deficiency:
-most common urea cycle disorder; X-linked recessive
-can't eliminate ammonia, can't make urea
-excess carbamoyl phosphate is converted to orotic acid (part of the pyrimidine synthesis pathway!)

229

Why may a B6 deficiency lead to seizures?

B6 is a cofactor in the formation of GABA from Glutamate (via glutamate decarboxylase)
-if B6 deficiency, then decrease GABA (inhibitory), so decreased inhibition --> increased neuroexcitability --> seizures.

230

Deficiency in phenylalanine hydroxylase?

PKU (enzyme that converts phenylalanine-->tyrosine hydroxylase in catecholamine synthesis; without it, get accumulation of phenylalanine and thus excess phenylketones in urine; tyrosine becomes essential)

231

"malignant phenylketonuria" cause?

deficiency/absence of THB (tetrahydrobiopterin cofactor), which is required for phenylalanine hydroxylase to convert Phenylalanine to tryosine, and tyrosine to Dopa

232

MR, growth retardation, seizures, fair skin, eczema, musty body odor

PKU (fair skin, because can't make dopa, and thus can't make melanin, b/c: dopa-->melanin)
-autosomal recessive

233

treatment for PKU

restrict phenylalanine in diet (aspartame); increase intake of tyrosine; also: give THB, if it's deficient.

234

dark connective tissue, brown pigmented sclera, urine turns black after prolonged exposure to air

Alkaptonuria; deficiency in homogentisic acid oxidase (degrades tyrosine-->fumarate)
-autosomal recessive; benign disease

235

Albinism causes? mode of inheritance?

Causes:
-tyrosinase deficiency (can't make melanin from tyrosine) = aut recessive
-defective tyrosine transporters (so decreased tyrosine-->decreased melanin)

236

tall stature, kyphosis, lens subluxation, atherosclerosis (stroke/MI), elevated levels of homocysteine in urine: Causes? Treatment?

-Homocystinuria = autosomal recessive
*Causes:
1) cystathionine synthase deficiency (treat: decrease Met, increased Cysteine, increased B12 and folate)
2) decreased affinity of cystathionine synthase for pyridoxal phosphate (active form of B6) (treat: increased B6 intake)
3) homocysteine methyltransferase deficiency

237

Lens subluxation:

-Marfan's
-Homocysteinuria

238

hexagonal cysteine crystals on urinalysis:

= pathognomonic for cystinuria

239

Cystinuria ("COLA defect")

defect in renal proximal tubules --> decreased reabsorption (so increased secretion) of COLA:
-Cysteine
-Ornithine
-Lysine
-Arginine

*autosomal recessive
*may lead to cystine kidney stones

240

Which amino acids should be avoided in maple syrup urine disease, and why?

Branched AA's: Ile, Leu, Val --> b/c deficiency of alpha-keotacid dehydrogenase, so can't degrade these AAs.