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27 Cards in this Set

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Phenylketonuria
- phenylalanine hydroxylase deficiency
- phenylalanine hydroxylase conversts phenylalanine to tyrosine
- tyrosine becomes essential AA and phenylalanine builds up

- symptoms: mental retardation, growth retardation, musty body odor
- treatment: decrease phenylalanine and increase tyrosine in diet
Alkaptonuria
- homogentisic acid oxidase deficiency
- homogentisic acid oxidase degrades tyrosine
- results in black urin, dark connective tissue and joint pain
Albinism
- deficiency in tyrosinase (makes melanin from tyrosine) or deficiency in tyrosine transporters (decreased amount of tyrosine and thus melanin)
- increased risk of skin cancer
Homocystinuria
- caused by either cystathione synthase deficiency, decreased affinity of cystathione synthase for pyridoxal phosphate, or homocystein methyltransferase deficiency

- results in excess homocysteine and cysteine becomes essential
- causes mental retardation, osteoporosis, tall stature, kyphosis, lens subluxation and atherosclerosis
Cystinuria
- common inherited defect of renal tubular amino acid transporter for cystein, ornithine, lysine and arginine in the PCT of the kidneys
- excess cystine in urine can lied to precipitation as cystine kidney stones (cystine is made of 2 cysteines connected by a disulfide bond)
Maple syrup urine disease
- blocked degradation of branched AAs (Ile, Val, Leu) due to decreased alpha-ketoacid dehydrogenase
- causes increased alpha-ketoacids in the blood, especially Leu
- causes severe CNS defects, mental retardation and death

- urine smells like maple syrup
- I Love Vermont maple syrup
Purine salvage deficiencies
- adenosine deaminase deficiency
- can cause SCID
- excess ATP and dATP imbalances nucleotide pool via feeback inhibition of ribonucleotide reductase (preventing DNA synthesis and thusly decreased lymphocyte count)

- Lesh-Nyhan syndrome
- HGPRT deficiency (converts hypoxanthine to IMP and guanine to GMP) causing excess uric acid production (because purines cannot be salvaged)
- symptoms: retardation, self-mutilation, aggression, hyperuricemia, gout, choreoathetosis
- HGPRT: He's Got Purine Recovery Trouble
Fasting and starvation
- Days 1-3
1. hepatic glycogenolyis and glucose release
2. adipose release of FFA
3. muscle and liver shifting fuel use from glucose to FFAs
4. hepatic gluconeogenesis

- After Day 3
muscle protein loss is maintained by hepatic formation of ketone bodies, supplying the brain and heart

- After several weeks
ketone bodies become main source of energy for brain, so less muscle protein is degraded than during days 1-3. after fat stores are depleted, vital protein degradation accelerates, leading to organ failure and death
Insulin
- made in beta cells of pancreas in response to ATP from glucose metabolism acting on K+ channels and depolarizing cells (required for adipose and skeletal muscle uptake of glucose)
- GLUT2 receptors are found in beta cells and GLUT4 in muscle/fat (GLUT1 in brain/RBCs)
- insulin inhibits glucagon release by alpha cells of pancreas
- serum C-peptide is not present with exogenous insulin intake (proinsulin --> insulin + C-peptide)
Glycogen
- branches have alpha-1,6 and linkages have alpha-1,4 bonds
Glycogen storage diseases
- Von Gierke's disease: glucose-6-phosphatase deficiency resulting in fasting hypoglycemia, increased glycogen in liver, increased blood lactate and hypatomegaly

- Pompe's disease: lysosomal alpha-1,4-glucosidase dificiency causing cardiomegaly and systemic findings leading to early death

- Cori's disease: debranching enzyme alpha-1,6-glucosidase deficiency causing a milder form of type 1 (VGD)with normal blood lactate levels

- McArdle's disease: skeletal muscle glycogen phosphorylase deficiency causing increased glycogen in muscle, but cannot break it down, leading to muscle cramps, myoglobinuria with strenous excersize

- Very Poor Carbohydrate Metabolism
Gaucher's disease
- lysosomal storage disease: beta-glucocerebrosidase deficiency (glucocerebroside builds up)
- symptoms: hepatosplenomegaly, aseptic necrosis of femur, bone crisis, Gaucher's cells (macrophages that look like crumpled tissue paper)
Tay-Sachs disease
- lysosomal storage disease: hexosaminidase A deficiency (GM2 ganglioside builds up)
- symptoms: progressive neurodegeneration, developmental delay, cherry red spot (on retina), lysosomes with onion skin
Fatty acid metabolism cites
- citrate shuttle: transports acetyl-CoA from the mitochondrial matrix to the cytoplasm for fatty acid synthesis
- carnitine shuttle: transports acyl-CoA (fatty acid + CoA) into mitochondrial matrix for breakdown (carnitine deficiency leads to an inability to utilize LCFAs and toxic accumulation)
Cholesterol synthesis
- HMG-CoA reductase: rate limiting enzyme, inhibitory target of statins
Essential fatty acids
- linoleic and linolenic acids (arachidonic acid, if linoleic acid is absent)
- eicosanoids are dependent of essential fatty acids
Lipoproteins (enzymes)
- Pancreatic lipase––degradation of dietary TG in small intestine.
- Lipoprotein lipase (LPL)––degradation of TG circulating in chylomicrons and VLDLs.
- Hepatic TG lipase (HL)––degradation of TG remaining in IDL.
- Hormone-sensitive lipase––degradation of TG stored in adipocytes.
- Lecithin-cholesterol acyltransferase (LCAT)––catalyzes esterification of cholesterol.
- Cholesterol ester transfer protein (CETP)––mediates transfer of cholesterol esters to other lipoprotein particles.
Major apolipoproteins
- A-I: activates LCAT
- B-100: Binds to LDL receptor, mediates VLDL secretion
- C-II: cofactor for lipoprotein lipase
- B-48: mediates chylomicron secretion
- E: mediates extra (remnant) uptake
LDL vs HDL
- LDL transports cholesterol from liver to tissue
- HDL transports cholesterol
from periphery to liver
- HDL is Healthy, LDL is Lousy
Chylomicrons
- secreted by intestinal epithelial cells
- deliver dietary triglycerids to peripheral tissues
- deliver cholesterol to liver in form of chylomicron remnants
Lipoproteins
- VLDL: delivers hepatic triglycerides to peripheral tissues
- IDL: delivers triglycerides and cholesterol to liver, where they are degraded to LDL (IDL is formed in the degeneration of VLDL)
- LDL: delivers hepatic cholesterol to peripheral tissues
- HDL: mediates centripetal transport of cholesterol (from periphery to liver)
Familial dyslipidemias
- Type I-hyperchylomicronemia: lipoprotein lipase deficiency or altered apolipoprotein C-II causes increased blood levels of chylomicrons (and thusly TG, cholesterol)

- Type IIa-hypercholesterolemia: ↓ LDL receptors cause increased LDL (and thusly cholesterol) in blood

- Type IV-hypertriglyceridemia: hepatic overproduction of VLDL causes increased circulating VLDL (and thusly TGs)
Porphyrias
- lead poisoning, acute intermittent porphyria, porphyria cutanea tarda

- symptoms: the 5 P's - Painful abdomen, Pink urine, Polyneuropathy, Psychological distrubances, Precipitated by drugs
Heme catabolism
- Heme → biliverdin → bilirubin
- bilirubin is removed from blood by liver, conjugated with glucuronate and excreted in bile
Hemoglobin

(composition, regulation, types)
- composed of 4 polypeptide subunits (2 α and 2 β)
- T (taut) form has low affinity for O2
- R (relaxed) form has high affinity for O2

- regulation: ↑ Cl−, H+, CO2, 2,3-BPG, and temperature favor T form over R form (shifts dissociation curve to your right, leading to ↑ O2 unloading).
- fetal hemoglobin (2α and 2γ) has lower affinity for 2,3-BPG than adult hemaglobin and thus has higher affinity for O2 (allowing it to "steal" O2 from maternal circulation)
CO2 transport in blood
- transported as bicarbonate
- transported by hemoglobin; binds to hemoglobin (not at O2 site)
Hemoglobin modifications
- Methemoglobin: oxidized form of hemoglobin (Fe3+ instead of Fe2+), treated with methylene blue

- carboxyhemoglobin: form of hemoglobin bound to CO in place of O2 (CO has 200x greater affinity than O2 for hemoglobin)