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80 Cards in this Set
- Front
- Back
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What are the essential amino acids? (must be in diet)
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- Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine
- Arginine is made in body but more is needed during rapid growth and recovery |
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What are the non-essential amino acids? (made in body)
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- Alanine, Asparagine, Aspartate, Cysteine, Glutamate, Glutamine, Glycine, Proline, Serine, Tyrosine
- Cysteine made from Methionine - Tyrosine made from Phenylalanine |
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What are the 3 carbon amino acids?
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Alanine
Serine Cysteine Glycine |
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What are the 3 carbon amino acids synthesized from?
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- pyruvate and phosphoglycerate
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What are the 4 carbon amino acids?
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- Asparagine and Aspartate
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What are the 4 carbon amino acids synthesized from?
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Oxaloacetate
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What are the 5 carbon amino acids?
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Glutamate
Glutamine Proline Arginine |
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What are the 5 carbon amino acids synthesized from?
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Alpha-Ketoglutarate
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What is Tyrosine synthesized from?
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The breakdown of phenylalanine through Phenylalanine hydroxylase and BH4
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What is the most common enzyme deficiency in Phenylalanine metabolism?
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Phenylalanine hydroxylase (Phenylalanine to tyrosine)
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What are some symptoms of defective Phe metabolism?
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- Elevated phenylalanine in blood, tissues, and urine (musty order)
- Progressive mental retardation - Seizures, hyperactivity, tremor, microcephaly, failure to grow |
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What enzyme is deficient in PKU?
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- Phenylalanine hydroxylase
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What enzyme is deficient in malignant PKU?
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-BH2 reductase that requires NADPH
or - BH4 synthesis that requires GTP |
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Treatment for PKU
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- Restrict phenylalanine
- Avoid Aspartame - Include Tyrosine in diet |
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What do glucogenic amino acids produce when degraded?
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- pyruvate or TCA cycle intermediates that will lead to glucose production in liver or oxidized for energy
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What do ketogenic amino acids produce when degraded?
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- acetyl-CoA, acetoacetate, or HMG-CoA that will lead to fatty acid synthesis or will be released by ketone bodies
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What is the main site of amino acid catabolism?
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the liver
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The degradation of Methionine produces...
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Cysteine
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What vitamins are used as cofactors during the degradation of Methionine?
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- Vitamin B12 (1st step)
- Vitamin B6 (second step...PLP) |
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What causes Homocystinuria?
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Deficiency in Cystathionine Beta- synthase
- 2nd step in Methionine degradation to Cysteine (conversion of homocysteine to cystathionine) |
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What causes Cystanthionuria?
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Deficiency in cystathionase
- 3rd step in Methionine degradation to Cysteine (converts cystathionine to cysteine) |
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What are the 4 disorders related to the degradation of Phenylalanine to Fumarate + Acetoacetate?
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- PKU
- Tyrosinemia II - Alcaptonuria - Tyrosinemia I |
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What causes Tyrosinemia II (Richner-Hanhart syndrome)?
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- defect in Tyrosine aminotransferase
- blocks Tyrosine -> p-Hydroxyphenylpyruvate |
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What are symptoms of Tyrosinemia II (Richner-Hanhart syndrome)?
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- neurological and pigmentation defects
- eye problems |
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What causes Alcaptonuria?
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- defect in homogentisate oxidase
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What are symptoms of Alcaptonuria?
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- arthritis and black urine
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What causes Tyrosinemia I?
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- Defect in fumarylacetoacetate hydrolase
- last enzyme in phenylalanine degradation |
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What are symptoms of Tyrosinemia I?
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- liver failure and early death
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What are the 3 universal steps in the degradation of branched chain amino acids?
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1) Transamination (converted to alph-keto acid)
2) Dehydrogenated (converted to CoA derivatives) 3) Beta-dehydrogenated by FAD-dehydrogenase |
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What are the products of the degradation of branched chain amino acids?
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Succinyl-CoA which goes to the TCA cycle
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What is Maple Syrup Urine Disease caused by?
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- defect in branched chain alpha-ketoacid dehydrogenase
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What are symptoms of Maple Syrup Urine Disease?
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- mental/physical retardation
- feeding problems - hypotonia or hypertonia - seizures - cerebral edema - maple syrup order to urine (b/c catabolism of the amino acids to sotolone) |
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Treatment of Maple Syrup Urine Disease?
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- dietary control of branched chain amino acids
- Thiamine supplementation - liver transplant - monitor levels of branched chain amino acids |
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What amino acids are in excess in Maple Syrup Urine Disease?
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- Leu, Iso, Val
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What amino acids concentrations are decreased in Maple Syrup Urine Disease?
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- Ala, Ser, Thr
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How many genes make up the Branched Chain Alpha-Keto acids dehydrogenase?
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- 4 genes, any can be defective to cause Maple Syrup Urine Disease
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What are the genes that make up the Branched Chain alpha Keto-acids dehydrogenase?
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1) BCKDHA
2) DBT 3) DLT 4) BCKDHB |
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Tyrosine can be used as a precursor for?
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- Catecholamines
- Melanoproteins |
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What is the rate determining step in the synthesis of Catecholamines from Tyrosine?
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1st step: Tyrosine to DOPA
- enzyme: Tyrosine hydroxylase - Cofactor: BH4 |
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How can DOPA levels determine type of PKU a patient has?
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- Conversion of Tyrosine to DOPA requires BH4 as a cofactor
- Low DOPA indicates malignant PKU b/c low BH4 |
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What is catecholamine is lost in Parkinson's disease?
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- Dopamine
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What are the 4 primary symptoms of Parkinson's?
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- tremors/trembling
- rigidity/stiffness - bradykinesia - postural instability |
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What environmental factors may be involved in Parkinson's disease?
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- viral infection (Flu epidemic of 1916-1919)
- Drugs such as MPTP (heroine contaminant) |
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Tryptophan is the precursor for?
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- Serotonin/melatonin
- Niacin (Vitamin B3) |
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What cofactors are required in the synthesis of Serotonin/Melatonin?
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- BH4
- PLP (Vitamin B6) |
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How is Serotonin converted into Melatonin?
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- methylation through SAM
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What does Serotonin do?
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- involved in brain function
- potent vasoconstrictor - stimulates contraction of smooth muscles |
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What does melatonin do?
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- involved in circardiam rhytmn
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What is the first step in the synthesis of Melanins?
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- Conversion of Tyrosine to DOPA
- Enzyme: Tyrosinase |
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What causes Albinism?
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- Defect in Tyrosinase
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What are the 3 types of Melanins?
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1) Eumelanin: hair/skin (grey, black, yellow, brown)
2) Pheomelanin: hair/skin (pink, red) 3) Neuromelanin: dark pigment in neurons |
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How much of the required niacin (Vitamin B3) is made from tryptophan?
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50% +
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What is an important intermediate in Tryptophan degradation to niacin?
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Kynurenine
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What functions does Kynurenines have?
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- Neuroactive (may be protective/toxic)
- immunoregulatory functions |
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What enzyme is used to break Tryptophan into Kynurenine?
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IDO
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What is IDO (for tryptophan degradation to Niacines) induced by?
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-IFN-y (cytokine that stimulates the immune system)
- modulating IDO may have an immpact on CNS diseases |
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What are the precursors of Heme?
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- Succinyl CoA
- Glycine |
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Where is the heme pathway regulated at?
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- 1st step from Succinyl CoA+Glycine to Aminolevulinic Acid
- Inhibited by Heme |
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What effect does lead poisoning have on the heme pathway?
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- inhibits 2 steps
1) 2nd step, ALA dehydratase 2) last step, ferrochetalase (adds Fe) |
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What are porphyrias and what are they caused by?
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- inborn errors of prophyrin metabolism
- deficiency in a heme biosynthetic enzyme |
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What can a deficiency of tryptophan lead to?
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- deficiency of Niacin= pellegra
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What is the most common prophyria (according to syllabus)?
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- Acute Intermittent porphyria
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What causes Acute Intermittent porphyria?
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- Defect in porphobilinogen deaminase
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What is increased in Acute Intermittent porphyria?
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- ALA and PBG (porphobilinogen)
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What causes Porphyria cutanea tarda?
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- Defect in uroporphyrinogen decarboxylase
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What is increased in Porphyria cutanea tarda?
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- Uroporphyrin I
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What causes Erythropoietic protoporphyria?
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- defect in ferrochelatase
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What is increased in Erythropoietic protoporphyria?
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- Protoporphyrin IX
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What are symptoms of porphyrias?
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- cutaneous photosensitivity (swelling, redness, fever, leathery skin, chronic blistering)
- Neurovisceral manifestations (confusion, hypertension, increased heart rate, weakness, abdominal pain, etc) |
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Symptoms of Acute Intermittent porphyria?
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- neurovisceral symptoms
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Symptoms of Porphyria cutanea tarda?
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- blistering skin
- lesions |
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What are symptoms of erytropopietic protoporphyria?
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- painful skin and swelling
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How is heme catabolized?
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1) oxidized to biliverdin
2) Forms bilirubin (in tissue) 3) Bilirubin bound to albumin for transport to liver 4) Bilirubin conjugated with glucuronic acid and is soluble (liver) 5) Goes into bile and travels into small intestine 6) Metabolized and mainly ends up in feces, small amount in urine |
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What (in general) causes jaundice?
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- elevated levels of bilirubin in blood
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What are the 3 main categories of jaundice?
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1) Hepatocellular jaundice
2) Obstructive jaundice 3) Hemolytic jaundice |
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What causes hepatocellular jaundice?
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- glucuronate conjugating system (makes bilirubin water soluble) and albumine synthesis (transport to blood) are impaired
- RARE |
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What causes obstructive jaundice?
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- Block in the bile duct so conjugated bilirubin leaks into circulatory
- may be caused by hepatitis, alcoholism, cirrhosis |
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What causes hemolytic jaundice?
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- G6PD deficiency (first step in pentose pathway to protect cells against oxidative stress)
- may cause hemolytic anemia= abnormal destruction of RBCs leading to increase in bilirubin |
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Why do newborns often suffer from temporary jaundice?
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- increased breakdown of fetal hemoglobin
- Bilirubin glucoroynl transferase levels are lower at birth |
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Why is newborn jaundice potentially dangerous?
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- Unconjugated bilirubin can cross blood-brain barrier and lead to toxic encephalopathy
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