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Biochem 4 Flashcards

1
Q

Phenylketonuria path

A

Decreased Phe hydroxylase or dec. tetrahydrobiopterin cofactor (malignant PKU)

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2
Q

What is malignant PKU?

A

Neonatal PKU due to tetrahydrobiopterin (BH4) deficiency

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3
Q

Phenylketonuria labs

A

excess phenylketones in urine

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4
Q

PKU presentation

A

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

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5
Q

PKU tx

A

decrease Phe and increase tyrosine in diet

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6
Q

what amino acid is essential in PKU

A

tyrosine before essential

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7
Q

PKU genetics

A

aut. rec. (1/10,000)

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8
Q

When does PKU appear

A

2-3 days after birth (enzyme from mother)

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9
Q

What are the phenylketones

A

phenylacetate, phenyllactate, and phenylpyruvate

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10
Q

Maternal PKU path and presetnation

A

lack of proper diet therapy during pregnancy. Infant has microcephaly, intellectula disability, growth retardation, congenital heart defects.

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11
Q

Alkaptonuria alternate name

A

Ochronosis

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12
Q

Homocystinuria types and genetics

A

3 types. All aut. rec.

  1. Cystathionine synthase deficiency
  2. Decreased affinity of cystathionine synthase for pyridoxal phosphate
  3. Homocysteine methyltransferase (methionine synthase) deficiency
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13
Q

Homocystinuria presentation

A

All forms result in excess homocysteine. MR, osteoporosis, tall stature, kyphosis, lens subluxation downward and inward, thrombosis, and atherosclerosis (stroke and MI)

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14
Q

Homocystinuria labs

A

elevated homocysteine in urine

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15
Q

Cystathionine synthase deficiency tx

A

lower methionine, increase cysteine, increase b12 and folate in diet

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16
Q

decreased affinity of cystathionine synthase for pyridoxal phosphate tx

A

increased b6 and cysteine in diet

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17
Q

homocysteine methyltransferase deficiency tx

A

increase methionine in diet

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18
Q

why does adding cysteine and methionine help with homocystinuria………

A

Not because it reverses any issues with homocysteine, it just helps in supplying methionine and cysteine which are needed in our bodies!

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19
Q

Cystinuria genetics and path

A

Aut. rec. (Common 1:7,000) hereditary defect of renal PCT and intestinal amino acid transporter for Cysteine, ornithine, Lysine, and Arginine (COLA)

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20
Q

Cystinuria presentation

A

Excess cystine in urine can lead to precipitation of hexagonal cystine stones

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21
Q

Cystinuria labs

A

urinary cyanide-nitroprusside test is diagnostic

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22
Q

Cystinuria tx

A

urinary alkalinization (e.g. potassium citrate, acetazolamide) and chelating agents increase solubility of cystine stones; good hydration

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23
Q

What is a cystine bond

A

2 cysteines connected with a disulfide bond

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24
Q

Maple syrup urine disease genetics and path

A

Aut. rec. Blocked degradation of branched amino acids (isoleucine, leucine, valine) due to decreased alpha-ketoacid dehydrogenase (B1). Causes increased alpha-ketoacids in blood especially leucine.

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25
Q

Maple syrup urine disease presentation and treatment

A

Causes severe CNS defects, intellectual disability, death.
I Love Vermont maple syrup (Isoleucine, leucine, valine)
restrict BCAAs and supplment thiamine

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26
Q

What pathway does glucagon activate

A

Binds glucagon receptor in liver activating adenylate cyclase leading to increased cAMP activating Protein kinase A activating glycogen phosphorylase kinase phosphorylating glycogen phosphorylase forming more glucose. Protein Kinase A also inhibits glycogen synthase.

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27
Q

What does PKA end up doing

A

Activates glycogen phosphorylase kinase and blocks glycogen synthase

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28
Q

What pathways does epinephrine activate

A

Binds beta-receptor in liver and muscle to activate the adenylate cyclate pathway like glucagon. In the liver, it also releases calcium from the ER activating glycogen phosphorylase kinase. Calcium-calmodulin is activated in muscle contraction and also activates glycogen phosphorylase kinase.

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29
Q

What pathway does insulin activate

A

Binds Tyrosine kinase dimer receptor and activates glycogen synthase and protein phosphatase to block glycogen phosphorylase.

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30
Q

What are the bonds in glycogen

A

alpha-(1,6) bonds for branches and linkages are alpha-(1,4) bonds

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31
Q

Glycogen metabolism in skeletal muscle

A

Glycogenolysis to glucose-1-P to glucose-6-P to be used up

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32
Q

How is glycogen cleaved up

A

glycogen phosphorylase cleaves off glucose-1-P off branches until there are 4 glucoses left. Then 4-alpha-D-glucanotransferase moves 3 glucoses off the branch to the linkage. Then alpha-1,6-glucosidase cleaves off the last glucose-1-P on the branch

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33
Q

What is a limit dextrin

A

The 1-4 residues on a branch after glycogen phosphorylase has already shortened it

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34
Q

What are the debranching enzymes

A

4-alpha-D-glucanotransferase and alpha-1,6-glucosidase

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35
Q

How to build glycogen

A

UDP-glucose is formed by UDP-glucose pyrophosphorylase from glucose-1-P.

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36
Q

What is acid maltase

A

In lysosomes, it is alpha-1,4-glucosidase. A small amount of glycogen is degraded in lysosomes.

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37
Q

Glycogen storage diseases mnemonic

A

Very Poor Carbohydrate Metabolism (Von Gierke, Pompe, Cori, McArdle)

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38
Q

Von Gierke disease (type 1) presentation

A

Severe fasting hypoglycemia, increased glycogen in liver, increased blood lactate, hepatomegaly

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39
Q

Von Gierke path and genetics

A

aut. rec. glucose-6-phosphatase absence

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40
Q

Von Gierke tx

A

frequent oral glucose/cornstarch; avoid fructose and galactose

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41
Q

Why avoid fructose and galactose in Von Gierkes?

A

Galactose, fructose, and glycerol are metabolized to lactate causing metabolic acidosis.

42
Q

Pompe disease presentation (type II)

A

Cardiomyopathy and systemic findings leading to early death

43
Q

Pompe path

A

Lysosomal alpha-1,4-glucosidase (acid maltase)

44
Q

Pompe genetics and mnemonic

A

Aut. rec.

Pompe trashes the Pump (heart, liver, and muscle)

45
Q

Cori disease (type III) presentation

A

Milder form of type I with normal blood lactate levels.

46
Q

Cori disease path

A

debranching enzyme (alpha-1,6-glucosidase). GNG is intact

47
Q

Cori diease genetics

A

aut. rec.

48
Q

McArdle disease (type V) presentation

A

Increased glycogen in muscle but cannot break it down, leading to painful muscle cramps, myoglubinuria (red urine) with strenuous exercise, and arrhthmia from electrolyte abnormalities

49
Q

McArdle disease path

A

Skeletal muscle glycogen phosphorylase (myophosphorylase)

50
Q

McArdle disease genetics

A

Autosomal recessive. (McArdle=Muscle)

51
Q

What is the basis of lysosomal storage diseases

A

Deficiency in one of many lysosomal enzymes. Results in accumulation of abnormal metabolic products)

52
Q

fabry disease enzyme and substrate

A

alpha-galactosidase A builds up Ceramide trihexoside

53
Q

Gaucher dz enzyme and substrate

A

glucocerebrosidase (beta-glucosidase) builds up glucocerebroside

54
Q

niemann-pick disease enzyme and substrate

A

Sphingomyelinase and sphingomyelin

55
Q

Tah-Sachs disaease enzyme and substrate

A

hexosaminidase A and GM2 ganglioside (AR)

56
Q

Krabbe disease enzyme and substrate

A

galactocerebrosidase and galactocerebroside, psychosine

57
Q

Metachromatic leukodystrophy enzyme and substrate

A

arylsulfatase A and cerebroside sulfate

58
Q

Hurler syndrome enzyme and substrate

A

alpha-L-iduronidase and heparan sulfate, dermatan sulfate

59
Q

Hunter syndrome enzyme and substrate

A

iduronate sulfatase and heparan sulfate, dermatan sulfate

60
Q

Mnemonic for lysosomal storage diseases

A
  1. No man picks (Niemann-Pick) his nose with his sphinger (sphinogomyelinase)
  2. Tay-SaX lacks heXosaminidase
  3. Hunters see clearly (no corneal clouding) and aggressivly aim for the X (X-linked recessive)
61
Q

Which lysosomal storage diseases are higher in Ashkenazi Jews

A

Tay-Sachs, Niemann-Pick, and some forms of Gaucher disease

62
Q

What makes acyl-CoA

A

Fatty acid CoA synthetase

63
Q

What blocks the carnitine shuttle

A

Malonyl CoA

64
Q

Where are fatty acids synthesized

A

In the cytosol

65
Q

What is the basic pathway for fatty acid synthesis

A

citrate from mitochondrial matrix moves via the citrate shuttle to produce acetyl-CoA via ATP citrate lyase, combines with CO2 (biotin) to produce malonyl-CoA which provides 2 carbons to fatty acid synthesis

66
Q

What is the end product of fatty acid synthesis

A

Palmitate a 16C FA

67
Q

Metabolism of ketone bodies

A

in liver, fatty acids and amino acids broken down to acetoacetate and beta-hydroxybutyrate (used in muscle adn brain)

68
Q

What happens in prolonged starvation and DKA

A

OAA depleted for GNG.

69
Q

What happens in alcoholism

A

Excess NADH shunts oxaloacetate to malate.

70
Q

What happens in both starvation, DKA, and alcoholism

A

Buildup acetyl-CoA which shutns glucose and FFA towards production of ketone bodies

71
Q

Urine test for ketones doesn’t detect what

A

Beta-hydroxybutyrate

72
Q

When starving for 1-3 days what happens to energy usage

A

Muscle and liver shift to use FFA from glucose

73
Q

Hepatic GNG sources

A

peripehral tissue lactate and alanine and adipose tissue glycerol and propionyl-CoA (from odd-chain FFA)

74
Q

how long to deplete glycogen reserves

A

After day 1

75
Q

Can RBCs use ketones?

A

No, they lack mitochondria

76
Q

Starvation after 3 days energy stores

A

Adipose stores (ketone bodies become the main source of energy for the brain)

77
Q

Cholesterol synthesis rate limiting step

A

Catalyzed by HMG-CoA reductase (induced by insulin), which converts HMG-CoA to mevalonate. 2/3 of plasma cholesterol is esterified by lecithin-cholesterol acyltransferase (LCAT)

78
Q

What do statins to

A

Competitively and reversibly inhibit HMG-CoA reductase

79
Q

Pathway of chylomicrons

A

Broken down by lipoprotein lipase into chylomicron remnants which are broken down further by LPL and hepatic TG lipase and then taken up by liver remnant receptors.

80
Q

Pathway of VLDL

A

VLDL broken down by LPL to release FFA to adiopose and peripheral tissues with LDL receptors to produce IDL. IDL is broken down by HL to LDL which can be taken up by peripheral tissues or brought back to liver.

81
Q

What is hormone sensitive lipase

A

In adipocytes and breakdown TG

82
Q

Pathway of a nascent HDL

A

Transformed by LCAT (lecithin-cholesterol acyltransferase) (esterifies cholesterl) to form mature HDL which can return to liver or through CETP (cholesterol ester transfer protein) which mediates transfer of cholesterol esters to other lipoprotein particles like VLDL, IDL, and LDL

83
Q

What is the purpose of CETP?

A

It transports cholesterol esters to LDL and VLDL and accepts TGs. CETP inhibitors increase HDL and lower LDL levels, but the effect is useless.

84
Q

What is the purpose of LCAT?

A

LCAT allows for the formation of mature HDL. It turns free cholesterol from the gut and peripheral tissues into the esterified form which can be carried by HDL back to the liver! or to be processed by CETP to add cholesterol to the other lipoproteins.

85
Q

ApoE function

A

Mediates remnant uptake

86
Q

ApoA-I function

A

Activates LCAT

87
Q

ApoC-II function

A

Lipoprotein lipase cofactor

88
Q

ApoB-48 function

A

Mediates chylomicron secretion

89
Q

ApoB-100 function

A

Binds LDL receptor.

90
Q

What lipoproteins carry most cholesterol

A

LDL and HDL

91
Q

What does LDL and HDL do

A

Both transport cholesterol, LDL to tissues and HDL back to liver

92
Q

Chylomicron source

A

Delivers dietary TGs to peripheral tissue. Secreted by intestinal epithelial cells.

93
Q

VLDL function

A

delivers Hepatic TGs to peripheral tissue. secreted by liver.

94
Q

IDL function

A

Delivers TGs and cholesterol to liver

95
Q

LDL function

A

delievers hepatic cholesterol to periphery. Formed by hepatic lipase modification of IDL in the peripheral tissue. Taken up by target cells via receptor-mediated endocytosis.

96
Q

HDL function

A

Repository for apoC and apoE which are needed for chylomicron and VLDL metabolism. Secreted from both liver and intestine. Alcohol increases synthesis.

97
Q

Type I: Hyper-chylomicronemia presentation

A

Increased chylomicrons, TG, and cholesterol

98
Q

Type IIa: familial hyper-choletserolemia presentation

A

Increased LDL, choelsterol

99
Q

Type IV: hypertriglyceridemia presentation

A

Increased VLDL and TG

100
Q

What is tetrahydrobiopterin

A

BH4. Used in aromatic amino acid hydroxylase enzymes. Made from guanosine triphosphate.

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