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biochem: metabolism Flashcards

1
Q

kinase

A

used ATP to add a (high E) phosphate group

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2
Q

phosphorylase

A

adds inorganic phosphate w/o ATP

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3
Q

phosphatase

A

removes phosphate group

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4
Q

dehydrogenase

A

catalyzes redox rxns

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5
Q

hydroxylase

A

adds -OH

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6
Q

carboxylase

A

transfers CO2 groups w/help from biotin

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7
Q

mutase

A

relocates a fxnal group w/in a molecule

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8
Q

mitochondrial metabolism

A

fatty acid oxidation (beta-oxidation), acetyl-CoA production, TCA cycle, oxidative phosphorylation, ketogenesis

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9
Q

cytoplasmic metabolism

A

glycolysis, fatty acid synthesis, HMP shunt, protein synthesis (RER), steroid synthesis (SER), cholesterol synthesis

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10
Q

mitochondrial AND cytoplasmic metabolism

A

HUGS take two: Heme synthesis, Urea cycle, Gluconeogenesis

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11
Q

glycolysis rate-limiting enzyme

A

PFK-1

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12
Q

glycolysis regulators

A

+: AMP, fructose-2,6-bisphosphate. -: ATP, citrate

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13
Q

gluconeogenesis rate-limiting enzyme

A

fructose-1,6-bisphosphatase

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14
Q

gluconeogenesis regulators

A

+: ATP, acetyl-CoA. -: AMP, fructose-2.6-bisphosphate

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15
Q

TCA cycle rate-limiting enzyme

A

isocitrate dehydrogenase

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16
Q

TCA cycle regulators

A

+: ADP. -: ATP, NADH

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17
Q

glycogenesis rate-limiting enzyme

A

flycogen synthase

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18
Q

glycogenesis regulators

A

+: G6P, insulin, cortisol. -: epinephrine, glucagon

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19
Q

glycogenolysis rate-limiting enzyme

A

glycogen phosphorylase

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20
Q

glycogenolysis regulators

A

+: epinephrine, glucagon, AMP. -: G6P, insulin, ATP

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21
Q

HMP shunt rate-limiting enzyme

A

G6PD

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22
Q

HMP shunt regulators

A

+:NADP+. -: NADPH

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23
Q

de novo pyrimidine rate-limiting enzyme

A

carbamoyl phosphate synthetase II

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24
Q

de novo pyrimidine regulators

A

+: ATP. -: UTP

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25
Q

de novo purine synthesis rate-limiting enzyme

A

PRPP amidotransferase

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26
Q

de novo purine synthesis regulators

A

-: AMP, inosine monophosphate (IMP), GMP

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27
Q

urea cycle rate-limiting enzyme

A

carbamoyl phosphate synthetase I

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28
Q

urea cycle regulators

A

+: N-acetylglutamate

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29
Q

fatty acid synthesis rate-limiting enzyme

A

acetyl-CoA carboxylase (ACC)

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30
Q

fatty acid synthesis regulators

A

+: insulin, citrate. -: glucagon, palmitoyl-CoA

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31
Q

fatty acid oxidation rate-limiting enzyme

A

carnitine acyltransferase I

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32
Q

fatty acid oxidation regulators

A

-: malonyl-CoA

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33
Q

ketogenesis rate-limiting enzyme

A

HMG-CoA synthase

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34
Q

cholesterol synthesis rate-limiting enzyme

A

HMG-CoA reductase

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35
Q

cholesterol synthesis regulators

A

+: insulin, thyroxine. -: glucagon, cholesterol

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36
Q

aerobic glucose metabolism

A

net + 32 ATP via malate-aspartate shuttle (heart and liver), 30 net ATP via glycerol-3-phosphate shuttle (muscle)

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37
Q

anaerobic glycolysis

A

net + 2 ATP/glucose

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38
Q

arsenic

A

causes glycolysis to produce 0 net ATP. inhibits lipoic acid. -> vomiting, rice-water stools, garlic breath

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39
Q

activated ATP carries

A

phosphoryl groups

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40
Q

activated NADH, NADPH, FADH2 carry

A

electrons

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41
Q

activated CoA, lipoamide carry

A

acyl groups

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42
Q

activated biotin carries

A

CO2

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43
Q

activated tetrahydrofolates carry

A

1-C units

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44
Q

activated S-adenosylmethionine (SAM) carries

A

CH3 groups

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45
Q

activated TPP carries

A

aldehydes

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46
Q

NADPH

A

= product of HMP shunt. used in: anabolic processes, respiratory burst, cytochrome P-450 system, glutathione reductase

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47
Q

universal electron acceptors

A

NAD+ (from vit B3), NADP+, FAD+ (from vit B2)

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48
Q

NAD+ vs. NADPH

A

NAD+: generally catabolic, carries reducing equivalents away. NADPH: generally anabolic (e.g. steroid and fatty acid synthesis), supplies reducing equivalents

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49
Q

hexokinase

A

in most tissues except liver and pancreatic beta cells. low Km (high affinity), low Vmax (low capacity), not induced by insulin. + feedback inhibition by G6P.

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50
Q

glucokinase

A

in liver, pancreas beta cells. high Km (low affinity), high Vmax (high capacity), induced by insulin. no feedback inhibition by G6P. gene mutation associated w/maturity-onset diabetes of the young

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51
Q

hexokinase vs. glucokinase

A

both can phosphorylate glucose into G6P: 1st step of glycolysis or glycogen synthesis. low [glu], hexokinase sequesters it in tissues. high [glu], liver stores it

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52
Q

FBPase-2 and PFK-2 in fasting state

A

inc. glucagon -> inc. cAMP -> inc. PKA -> inc. FBPase-2, dec. PFK-2, less glycolysis, more gluconeogenesis

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53
Q

FBPase-2 and PFK-2 in fed state

A

inc. insulin -> dec. cAMP -> dec. PKA -> dec. FBPase-2, inc. PFK-2, more glycolysis, less gluconeogenesis

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54
Q

pyruvate dehydrogenase complex

A

mitochondrial enzyme complex linking glycolysis and TCA cycle. active in fed state. similar to alpha-detoglutarate dehydrogenase complex in TCA cycle. 3 enzymes, 5 cofactors: pyrophosphate, FAD, NAD, CoA, and lipoic acid. exercise -> inc. NAD+/NADH ratio, inc. ADP, inc. Ca 2+ -> activation of complex.

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55
Q

pyruvate dehydrogenase complex deficiency

A

causes buildup of pyruvate that gets shunted to lactate via LDH and alanine via ALT. X-linked

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56
Q

pyruvate dehydrogenase complex deficiency: findings

A

neurologic defects, lactic acidosis, inc. serum alanine. starts in infancy

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57
Q

pyruvate dehydrogenase complex deficiency: Tx

A

inc. intake of ketogenic nutrients (high fat, high lysine and leucine). Lysine and Leucine - the onLy pureLy ketogenic AAs.

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58
Q

4 possible products of pyruvate

A

alanine, oxaloacetate, acetyl-CoA, lactate

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59
Q

pyruvate -> alanine

A

via alanine aminotransferase (ALT) w/B6. alanine carries amino groups to liver from muscle. in cytosol

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60
Q

pyruvate -> oxaloacetate

A

via pyruvate carboxylase (PC) w/biotin. oxaloacetate can replinish TCA cycle of be used in gluconeogenesis. requires CO2 and ATP. in mitochondria

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61
Q

pyruvate -> acetyl-CoA

A

via pyruvate dehydrogenase (PDH) w/B1, B2, B3, B5, lipoic acid. transition from glycolysis to TCA cycle. NAD+ in, NADH, H+, and CO2 out. occurs in mitochondria.

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62
Q

pyruvate -> lactate

A

= cori cycle. via LDH w/B3. end of anaerobic glycolysis, the major pathway in RBCs, WBCs, kidney medulla, lens, testes, and cornea.

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63
Q

krebs cycle mnemonic

A

Citrate Is Krebs’ Starting Substrate For Making Oxaloacetate: Citrate, Isocitrate, alpha-Ketoglutarate, Succinyl-CoA, Succinate, Fumarate, Malate, Oxaloacetate

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64
Q

TCA cycle produces

A

3 NADH, 1 FADH2, 2CO2, 1 GTP per acetyl-CoA = 10ATP/acetylCoA (2x/glucose).

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65
Q

e- transport chain: ox phos

A

NADH electrons from glycolysis enter mitochondria via shuttles to complex I. FADH2 electrons are transferred to complex II (lower E than NADH). electron transport creates a proton gradient that is coupled w/ox phos to drive ATP production

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66
Q

NADH -> _ATP

A

2.5ATP

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67
Q

FADH2 -> _ATP

A

1.5ATP

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68
Q

electron transport inhibitor poisons

A

rotenone, cyanide, antimycin A, CO. directly inhibit electron transport, causing a dec. proton gradient and block of ATP synthesis

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69
Q

ATP synthase inhibitor poisons

A

oligomysin. directly inhibit mitochondrial ATP synthase, causing an inc. proton gradient. no ATP is produced b/c electron transport stops

70
Q

uncoupling agent poisons

A

2,4-dinitrophenol (illicit wt. loss drug), aspirin (OD -> fever), thermogenin in brown fat. inc. permeability of membrane causes dec. proton gradient and inc. O2 consumption. ATP synthesis stops, but electron transport continues. produces heat.

71
Q

irreversible enzymes in gluconeogensis

A

Pathway Produces Fresh Glucose: Pyruvate carboxylase, Phosphoenolpyruvate, Fructose-1,6-bisphosphatase, Glucose-6-phosphatase.

72
Q

pyruvate carboxylase

A

in mitochondria. pyruvate -> oxaloacetate. requires biotin, ATP. activated by acetyl-CoA

73
Q

phosphoenolpyruvate carboxykinase

A

in cytosol. oxaloacetate -> phosphoenolpyruvate. requires GTP

74
Q

fructose-1,6-bisphosphatase

A

in cytosol. fructose-1,6-bisphosphate -> fructose-6-phosphate. +: citrate. -: 2,6-bisphosphate

75
Q

glucose-6-phosphatase

A

in ER. G6P -> glucose

76
Q

gluconeogenesis

A

occurs primarily in liver. maintains euglycemia during fasting. enzymes are also in kidney, intestinal epithelium. enzyme deficiency -> hypoglycemia. muscle can’t do it b/c it has no G6Pase. only odd-chain fatty acids can participate, even chains can’t b/c they yield acetyl-CoA instead of propionyl-CoA, which enters as succinyl-CoA

77
Q

HMP shunt

A

provides NADPH from G6P. also makes ribose for NA synthesis and glycolytic intermediates. 2 phases: oxidative and non-oxidative. both occur in cytoplasm in lactating mammary glands, liver, adrenal cortex, RBCs. no ATP is used or made.

78
Q

oxidative phase of HMP shunt

A

G6P dehydrogenase converts G6P -> ribulose-5-P, yielding CO2 and 2 NADPH. rate-limiting step. irreversible

79
Q

nonoxidative phase of HMP shunt

A

phosphopentose isomerase and transketolases convert ribulose-5-P -> ribose-5-P, G3P and fructose-6-P. reversible. requires B1

80
Q

G6P dehydrogenase deficiency

A

can’t make NADPH, so can’t keep glutathione reduced, so free radicals accumulate. In RBCs, this causes hemolytic anemia, worsened by fava beans, sufas, primaquine, TB drugs, infection, inflammation. X-linked recessive. most common in AAs - inc. malarial resistance. will see heintz bodies and bite cells

81
Q

essential fructosuria

A

defective fructokinase. autosomal recessive. benign, asymptomatic. fructose d/os are milder than analagous galactose d/os

82
Q

fructose intolerance

A

autosomal recessive aldolase B deficiency. fructose-1-P accumulates in cells -> dec. available phosphate -> inhibition of hlycogenolysis and gluconeogenesis. Sx present after consuming fruit, juice, or honey. Udip = neg but regucing sugar can be detected in urine. Sx: hypoglycemia, jaundice, cirrhosis, vomiting. Tx: avoid fructose and sucrose

83
Q

galactokinase deficiency

A

autosomal recessive. galactitol accumulates if galactose is consumed in diet. relatively mild. Sx: galactose in blood and urine, infantile cataracts, which can present as failure of social smile or object tracking

84
Q

classic galactosemia

A

autosomal recessive absence of galactose-1-phosphate uridyltransferase. toxic falactitol and other substances accumulate. Sx: FTT, jaundice, hepatomegaly, infantile cataracts, intellectual disability, E coli sepsis (commonly fatal). Tx: exclude falactose and lactose from diet. also causes phosphate depletion.

85
Q

fructose/galactose mnemonic

A

FAB GUT: Fructose is to Aldolase B as Galactose is to UridylTransferase

86
Q

sorbitol

A

= glucose’s alcohol counterpart. conversion via aldose reductase traps it inside the cell. some tissues (liver, ovaries, seminal vesicles) convert sorbitol -> fructose via sorbitol dehydrogenase. other tissues (schwann cells, retina, kidneys, lens) are at risk of accumulating sorbitol -> osmotic damage: cataracts, retinopathy, peripheral neuropathy, as seen w/chronic hyperglycemia in DM.

87
Q

types of lactase deficiency

A

primary: common. age-dependent decline after childhood 2/2 absense of lactase-persistent allele.
secondary: los of BB 2/2 gastroenteritis (e.g. rotavirus), autoimmune dz, etc.
congenital: rare, due to defective gene

88
Q

lactase deficiency

A

Dx: stool: low pH. breath: high hydrogen content following lactose tolerance test. intestinal Bx: normal (if congenital)
Sx: bloating, cramps, flatulence, osmotic diarrhea.
Tx: avoid dairy or take lactase pills

89
Q

essential AAs

A

need to be consumed in the diet.
glucogenic: methionine, valine, histidine
glucogenic/ketogenic: isoleucine, phenylalanine, threonine, tryptophan
ketogenic: leucine and lysine

90
Q

acidic AAs

A

aspartic acid, glutamic acid. negatively charged at normal pH

91
Q

basic AAs

A

arginine (most basic), lysine, histidine (no charge at normal pH). Arg and His are required during periods of growth. Arg and Lys are used by histones to bind - charged DNA

92
Q

urea cycle mnemonic

A

Ordinarily, Careless Crappers Are Also Frivolous About Urination: Ornithine, Citrulline, Aspartate, Argininosuccinate, Fumarate, Arginine, Urea

93
Q

urea cycle

A

AA catabolism -> formation of common metabolites (e.g. pyruvate, acetyl-CoA), which serve as fuels. this process generates excess NH3, which is converted to urea and excreted renally. substrates: NH3, CO2, ATP. products: urea, AMP, fumarate. takes place in the liver

94
Q

cahill cycle

A

alanine transports ammonia from muscle -> liver. alanine is converted to glucose to complete cycle.

95
Q

cori cycle

A

lactate (in muscle) -> lactate (in liver) -> pyruvate -> glucose (liver -> muscle) -> pyruvate -> lactate

96
Q

ammonia is carried by

A

glutamate (w/in cells) and alanine

97
Q

hyperammonemia

A

can be acquired (e.g. liver dz) or hereditary (e.g. urea cycle defects). -> excess NH4+, which depletes alpha-ketoglutarate, inhibiting the TCA cycle. Tx: limit protein intake. lactulose: acidified GI tract, trapping ammonia for excretion. rifampin: dec. colonic ammoniagenic bacteria. benzoate/phenylbutyrate: bind AAs -> excretion

98
Q

ammonia intoxication

A

tremor (asterixis), speech slurring, somnolence, vomiting, cerebral edema, vision blurring

99
Q

N-acetylglutamate synthase deficiency

A

required cofactor for carbamoyl phosphate synthetase I. absense -> hyperammonemia. presents in neonates as poorly regulated respiration and body T, poor feeding, dev. delay, intellectual disability. identical presentation to carbamoyl phosphate synthetase I deficiency

100
Q

ornithine transcarbamylase deficiency

A

X-linked (other urea cycle defects are autosomal recessive). most common urea cycle d/o. interferes w/ammonia excretion. often presents in 1st few days of life but can be later. excess carbamoyl phosphate -> orotic acid.
findings: inc. orotic acid in blood and urine, dec. BUN, Sx of hyperammonemia. NO megaloblastic anemia (vs. orotic aciduria).

101
Q

phenylalanine derivatives

A

tyrosine, thyroxine, melanin, dopamine, NE, epi

102
Q

tryptophan derivatives

A

niacin, 5HT, melatonin

103
Q

histidine derivative

A

histamine

104
Q

glycine derivatives

A

porphyrin, heme

105
Q

glutamate derivatives

A

GABA, glutathione

106
Q

arginine derivatives

A

creatine, urea, NO

107
Q

deficient enzyme in PKU

A

phenylalanine hydroxylase (phenylalanine -> tyrosine)

108
Q

deficient enzyme in albinism

A

tyrosinase (DOPA (dihydroxyphenylalanine) -> melanin)

109
Q

deficient enzyme in alkaptonuria

A

homogentisate oxidase (homogentisic acid -> maleylacetoacetic acid - part of tyrosine –> fumarate -> TCA cycle)

110
Q

phenylketonuria

A

autosomal recessive. tyrosine becomes essential. if due to missing tetrahydrobiopterin cofacter, called malignant PKU. findings: intellectual disability, growth retardation, seizures, fair skin, eczema, musty odor. Tx: dec. phenylalanine (aspartame) and inc. tyrosine in diet. supplement tetrahydrobiopterin. Aromatic AA -> odor! screening 2-3 days after birth (normal levels at birth)

111
Q

maternal PKU

A

lack of proper dietary therapy during pregnancy -> microcephaly, intellectual disability, growth retardation and congenital heart defects in baby

112
Q

maple syrup urine dz mnemonic

A

I Love Vermont maple syrup (trees have branches): blocked degradation of branches AAs Isoleucine, Leucine, and Valine

113
Q

maple syrup urine dz

A

dec. alpha-detoacid dehydrogenase (B1) -> inc. alpha-ketoacids in blood (esp. of leucine) -> severe CNS defects, intellectual disability, death. Tx: restrict isoleucine, leucine, and valine in diet, supplement thiamine

114
Q

alkaptonuria

A

= ochronosis. autosomal recessive deficiency of homogentisate oxidase -> tissue accumulation of pigment-forming homogentisic acid. usually benign. findings: dark connective tissue, brown pigmented sclerae, urine turns black when exposed to air. can cause debilitating arthralgia b/c homogentisic acid = toxic to cartilage

115
Q

homocystinuria types

A 
3 types, all autosomal recessive: 
cystathionine synthase deficinecy (Tx: dec. methionine, inc. cysteine, B12, and folate in diet)
dec. affinity of cystathionine synthase or pyridoxal phosphate (Tx: inc. B6 (lots) and cysteine in diet)
homocysteine methyltransferase (methionine synthase) deficiency (Tx: inc. methionine in diet)
116
Q

homocystinuria

A

-> excess homocysteine. findings: lots of homocysteine in urine, intellectual disability, osteoporosis, marganoid habitus, kyphosis, downward lens subluxation, thrombosis, atherosclerosis (stroke, MI)

117
Q

cystinuria

A

autosomal recessive, common defect of renal PCT and intestinal AA transporter that prevents reabsorption of COLA: Cysteine, Ornithine, Lysine, Arginine. excess urine cystine -> recurrent hexagonal kidney stones. Tx: urinary alkalinization (potassium citrate, acetazolamine), chelating agents (e.g. penicillamine) -> inc. solubility. good hydration. Dx: urinary cyanide-nitroprusside test

118
Q

cystine

A

2 cysteines connected by disulfide bond

119
Q

glycogen regulation by insulin

A

insulin binds tyrosine kinase dimer receptor in liver and muslce -> + glycogen synthase (glucose -> glycogen) and protein phosphatase (+ glycogen synthase, - glycogen phosphorylase). net: more glycogen

120
Q

glycogen regulation by glucagon

A

glucagon binds receptor in liver -> +cAMP -> +PKA -> + glucogen phosphorylase kinase -> glycogen phosphorylase (glucogen -> glucose). net: less glycogen, more glucose available

121
Q

glycogen regulation by epinephrine

A

binds beta receptor in liver and muscle -> +cAMP -> +PKA -> + glucogen phosphorylase kinase -> glycogen phosphorylase (glucogen -> glucose).
binds alpha receptor in liver -> ER releases Ca -> + glycogen phosphorylase kinase and +Ca-calmodulin in contracting muscle -> + glycogen phosphorylase kinase
net: less glycogen, more glucose available

122
Q

glycogen bonds

A

branches: alpha-(1,6) bonds. linkages: alpha-(1,4) bonds

123
Q

glycogen in skeletal muscle

A

glycogenolysis -> G1P -> G6P -> fuel

124
Q

glycogen in hepatocytes

A

stored. glycogenolysis to maintain normal blood sugar. glycogen phosphorylase frees G1Ps until 4 glucose per branch, then 4-alpha-D-glucanotransferase (debranching enzyme) moves 3 G1Ps from the branch to the linkage. then alpha-1,6-glucosidase (debranching enzyme) cleaves the last glucose - everything is free!

125
Q

limit dextrin

A

the 1-4 glucose residues that remain on a branch after glycogen phosphorylase has shortened it

126
Q

glycogen storage dzs

A

12 types, all causing glycogen accumulation in cells. Very Poor Carbohydrate Metabolism: Con gierke dz (type I), Pompe dz (type II), Cori dz (type III), McArdle dz (type V)

127
Q

von gierke dz

A

autosomal recessive. Sx: severe fasting hypoglycemia, inc. glycogen in liver, blood lactate, triglycerides, uric acid, and hepatomegaly. Tx: frequent oral glucose/cornstarch, avoid fluctose and galactose. deficient enzyme: G6Pase

128
Q

pompe dz

A

autosomal recessive. Pompe trashes the Pump (heart, liver, muscle). Sx: cardiomegaly, hypertrophic cardiomyopathy, exercise intolerance, early death. deficient enzyme: lysosomal alpha-1,4-glucosidase (acid maltase)

129
Q

cori dz

A

autosomal recessive. gluconeogenesis = intact. Sx: milder type I w/normal blood lactate levels. deficient enzyme: alpha-1,6-glucosidase (debranching enzyme)

130
Q

mcardle dz

A

autosomal recessive. Mcardle = Muscle. normal blood glucose. Sx: inc. glycogen in muscle (which can’t break it down) -> painful muscle cramps, myoglobinuria w/strenuous exercise, arrhythmia from electrolyte disturbance

131
Q

fabry dz

A

XR. sphingolipidosis. Sx: peripheral neuropathy of hands/feet, angiokeratomas, CV/renal dz. deficient enzyme: alpha-galactosidase A. accumulate: ceramide trihexoside

132
Q

gaucher dz

A

AR. most common. Sx: HSM, pancytopenia, osteoporosis, aseptic necrosis of femur, bone crises, gaucher cells (lipid-laden macrophages that look like crumpled tissue paper). Tx: recombinant glucocerebrosidase. deficient enzyme: glucocerebrosidase (beta-glucosidase). accumulate: glucocerebroside. inc. in ashkenazi

133
Q

niemann-pick dz

A

AR. sphingolipidosis. Sx: progressive neurodegeneration, HSM, foam cells, cherry-red macula. deficient enzyme: sphingomyelinase. accumulate: sphingomyelin. inc. in ashkenazi

134
Q

tay-sachs dz

A

AR. sphingolipidosis. Sx: progressive neurodegeneration, dev. delay, cherry-red macula, lysosomes w/onion skin, NO HSM. deficient enzyme: hexosaminidase A. accumulate: GM2 ganglioside. inc. in ashkenazi

135
Q

krabbe dz

A

AR. sphingolipidosis. Sx: peripheral neuropathy, dev. delay, optic atrophy, globoid cells. deficient enzyme: galactocerebrosidase. accumulate: galactocerebroside, psychosine

136
Q

metachromatic leukodystrophy

A

AR. sphingolipidosis. Sx: central and peripheral demyelination w/ataxia, dementia. deficient enzyme: arylsulfatase A. accumulate: cerebroside sulfate

137
Q

hurler syndrome

A

AR. mucopolysaccharidosis. Sx: dev. delay, gargoylism, airway obstruction, corneal clouding, HSM. deficient enzyme: alpha-L-iduronidase. accumulate: heparan sulfate, dermatan sulfate

138
Q

hunter syndrome

A

XR. mucopolysaccharidosis. Sx: mild hurler + agressive behavior. NO corneal clouding. deficient enzyme: deparan sulfate, dermatan sulfate

139
Q

lysosomal storage mnemonics

A

No man picks his nose w/his sphinger. tay-saX lacks heXosaminidase. hunters see clearly and aggressively aim for the X.

140
Q

fatty acid synthesis

A

SYtrate: SYnthesis. requires citrate transport from mitochondria to cytosol. occurs mostly in liver, lactating mammary glands, and adipose tissue. biotin = cofactor.

141
Q

fatty acid degradation

A

CARnitine: CARnage of fatty acids. long-chain FA degradation requires carnitine-dependent transport into mitochondrial matrix.

142
Q

systemic primary carnitine deficiency

A

inherited defect in LCFA transport into mitochondria -> toxic accumulations -> weakness, hypotonia, kypoketotic hypoglycemia

143
Q

medium-chain acyl-CoA dehydrogenase deficiency

A

AR d/o of fatty acid oxidation -> dec. ability to break down FA -> acetyl-CoA -> accumulation of 8-10C fatty acyl carnitines in blood and hypoketotic hypoglycemia. presents in infancy or early childhood w/vomiting, lethargy, seizures, coma, and liver dysfxn. minor illness can -> sudden death so don’t fast!

144
Q

ketone bodies

A

liver metabolizes FAs and AAs -> acetoacetate and beta-hydroxybutyrate to fuel muscle and brain. in starvation and DKA, oxaloacetate is depleted for gluconeogenesis. in alcoholism, excess NADH shunts oxaloacetate -> malate. both -> ateyl-CoA buildup, shunting glucose and FFAs -> ketone production. urine test for ketones doesn’t detect beta-hydroxybutyrate

145
Q

fasting priorities

A

supply glucose to the brain and RBCs, preserve protein

146
Q

fed state

A

glycolysis and aerobic respiration. insulin stimulates storage of lipids, proteins, and glycogen

147
Q

fasting state

A

hepatic glycogenolysis (major); hepatic gluconeogenesis, adipose release of FFAs (minor. glucagon and epinephrine stimulate use of fuel reserves

148
Q

starvation days 1-3

A

blood glucose maintained by: hepatic glycogenolysis, adipose release of FFAs, muscle and liver shift fuel use from glucose to FFA, hepatic gluconeogenesis for peripheral tissue lactate and alanine and propionyl-CoA (from odd chain FAs). glycogen reserves only last 1 day. RBCs have no mitochondria - can’t use ketones.

149
Q

starvation days 3+

A

adipose stores (ketones become main fuel for brain). after these are depleted, vital protein degradation accelerates -> organ failure + death. amount stored determines survival time.

150
Q

cholesterol

A

needed to maintain cell membrane integrity and to synthesize bile acid, steroids, and vit D

151
Q

cholesterol synthesis

A

rate-limiting step is catalyzed by HMG-CoA reductase (induced by insulin), which converts HMG-CoA -> mevalonate. 2/3 of plasma cholesterol = esterified by lecithin-cholesterol acyltransferase (LCAT)

152
Q

statin MoA

A

competitively and reversibly inhibit HMG-CoA reductase

153
Q

pancreatic lipase

A

degradation of dietary TGs in small intestine

154
Q

lipoprotein lipase (LPL)

A

degradation of TGs circulating in chylomicrons and VLDLs. found on vascular endothelial surface

155
Q

hepatic TG lipase (HL)

A

degradation of TGs remaining in IDL

156
Q

hormone-sensitive lipase

A

degradation of TGs stored in adipocytes

157
Q

LCAT

A

catalyzes cholesterol esterification

158
Q

cholesterol ester transfer protein (CETP)

A

mediates transfer of cholesterol esters to other lipoprotein particles

159
Q

apolipoprotein E

A

mediates remnant uptake. used by chylomicrons, chylomicron remnants, VLDL, IDL, and HDL (not LDL)

160
Q

apolipoprotein A-I

A

activates LCAT. used by chylomicrons and HDL

161
Q

apolipoprotein C-II

A

lipoprotein lipase cofactor. used by chylomicrons and VLDL

162
Q

apolipoprotein B-48

A

mediates chylomicron secretion. used by chylomicrons and chylomicron remnants

163
Q

apolipoprotein B-100

A

binds LDL receptor. used by VLDL, IDL, and LDL

164
Q

lipoprotein fxns

A

composed of varying proportions of cholesterol, TGs, and phospholipids. LDL and HDL carry the most cholesterol. LDL transports cholesterol from liver -> tissues. HDL transports cholesterol from periphery to liver.

165
Q

chylomicron

A

delivers dietary TGs to peripheral tissue. delivers cholesterol to liver in the form of chylomicron remnants, which are mostly depleted of their TGs. secreted by intestinal epithelial cells.

166
Q

VLDL

A

delivers hepatic TGs to peripheral tissue. secreted by liver.

167
Q

IDL

A

formed in the degradation of VLDL. delivers TGs and cholesterol to liver

168
Q

LDL

A

delivers hepatic cholesterol to peripheral tissues. formed by hepatic lipase modification of IDL in peripheral tissue. taken up by target cells via receptor-medicated endocytosis.

169
Q

HDL

A

mediates reverse cholesterol transport from periphery to liver. acts as a repository for apolipoproteins C and E (which are needed for chylomicron and VLDL metabolism). secreted from both liver and intestine. EtOH -> inc. synthesis.

170
Q

I: hyperchylomicronemia

A

AR. lipoprotein lipase deficiency or altered apolipoprotein C-II -> increased chylomicrons, TGs, and cholesterol in the blood -> pancreatitis, HSM, eruptive/pruritic xanthomas. NO inc. risk of atherosclerosis. creamy layer in supernatant.

171
Q

IIa: familial hypercholesterolemia

A

AD. absent or defective LDL receptors -> inc. LDL and cholesterol in blood -> accelerated atherosclerosis (may have MI before 20), tendon xanthomas, and corneal arcus. heterozygotes (1:500) have cholesterol ~300. homozygotes (very rare) have cholesterol ~700.

172
Q

IV: hypertriglyceridemia

A

AD. hepatic overproduction of VLDL -> inc. VLDL and TGs in blood. TG level >100 can cause acute pancreatitis

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