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Molecular Mechanisms > Block 1 Part 2 > Flashcards

Block 1 Part 2 Flashcards

1
Q

hormone CCK

A

cholesytokinin - produced by intestine when it senses FA - releases bile (amphipathic form of cholesterol)

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2
Q

secretin

A

hormone that stimulates pancreatic release of bicarbonate to neutralize stomach acid

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3
Q

orlistat

A

drug that inhibits all lipases

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4
Q

enzymes involved in fat metabolism

A 
cholesterol esterase (cholesterol ester to cholesterol); phospholipase A2 (removes last fatty acid on triglyceride - usually sn2 position)
lipase/co-lipase
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5
Q

function of enterocytes in TG metabolism

A

uptake, re-esterify FA and cholesterol –>chylomicrons (carry ApoB48) travel through lymph to blood, transporting triglycerides to adipose, muscle, and heart cells
Blood LPL rips off free FA from chylomicron—>FA to cells, leaving chylomicron remnants. Liver converts depleted chylomicron remnants into lipoproteins VLDL, uptakes LDL, secretes HDL

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6
Q

FA Synthesis

A

add 2C/cycle (requires transport into cytoplasm) Key players: mitochondrial ACC (acetyl CoA carboxylase, +biotin), cytosolic FA synthase (+biotin), Malate-Citrate Shuttle (transport from mt—>ct) 1. Mitochondria: Acetyl CoA+CO2—>malonyl CoA (via ACC) 2. Malate-Citrate shuttle: transports malonyl CoA from mitochondria into cytoplasm (citrate vs pyruvate transporter) 3. Cytoplasm: malonyl coA+acyl carrier+Acetyl CoA—> Palmitate (via FA synthase) *Each round adds 2C (from Acetyl CoA), generating Palmitate

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7
Q

enzymes involved in FA synthesis

A

acetyl coA carboxylase (ACC: acetyl coA -> malonyl coA)
malate-citrate shuttle
FA synthase (BIOTIN)

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8
Q

hormonal regulation of FA synthesis

A

insulin: activates phosphatase that activates ACC

glucagon/epinephrin: activate cAMP-dependent PKA - inactivates ACC

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9
Q

main enzymes involved in FA metabolism

A
  1. FA caA synthethase (outer membrane of mitochondria - “activates” FA by making FA coA it can now move into IM space)
  2. CPT1 (carnitine palmitoyl transferase - makes FAcarnitine that can move into matrix)
  3. CPTII (makes FA coA and carnitine in matrix)
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10
Q

beta oxidation

A

oxidize to double bond between alpha and beta; ox to hydroxyl; ox to carbonyl; thiolysis by coA –> FADH2, NADH2, acetyl coA
MCAD - medium chain acetyl dehydrogenase (makes a-b double bond)
LCAD - long chain …

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11
Q

hormonal regulation of beta ox

A
  1. insulin –> phosphatase –> ACC –> malonyl coA –| CPT1 –| beta ox
  2. glucagon/epinephrin –> PKA –| ACC – low levels of malonyl coA –> CPT1 active –> beta ox
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12
Q

ketone bodies

A

acetoacetate, beta hydroxybutyrate, acetone.
acetyl coA cannot enter TCA b/c oxaloacetate is depleted (used up in gluconeogenesis)
liver cannot use ketone bodies that well

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13
Q

MCADD

A

cannot reduce medium chain FAs into acyl CoA for beta oxidation
Labs: low ketones* (minimal ketones made), low glucose, accumulation of C8-acylcarnitine (confirm with mass spec, enzyme assay) *can still make minimal ketones (vs LCADD)
Clinical presentation: baby not fed overnight, presents with seizure in the AM

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14
Q

LCADD

A

can’t breakdown long chain FA into acyl CoA for beta oxidation
Labs: low glucose, NO ketones*, brown urine (rhabdomyolysis), accumulation of long chain FA (mass spec), confirm with enzyme assay *LC FA require LCAD for any beta oxidation/ketone generation
Clinical presentation: child with minor URI triggers crisis with fever, low PO intake, progressive sleepiness and difficult to arouse
FAOD Treatment: start high glucose ASAP, avoid fasting for >8- 12h, carnitine supplementation (maximize transport into mitochondria)
(muscle uses long chain; liver medium chain)

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15
Q

rhabdomyolysis

A

muscle breakdown

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16
Q

HMG coA reductase

A

enzyme for cholesterol synthesis

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17
Q

ACAT

A

converts free cholesterol in cytosol to lipid droplets

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18
Q

LDL uptake consequences

A

uptake by LDLR –> (-) HMG coA reductase activity; (+) ACAT activity

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19
Q

statins

A

inhibit HMGcoA reductase –> low intracellular cholesterol–> SRBP2 on –> (+) LDLR

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20
Q

SREBP Pathway

A

(+) LDLR and HMG coAR –> (-) plasma LDL; (+) Insig (inactivates SREBP = negative feedback)
activated by low cholesterol and insulin

low cholesterol -> SREBP activated, docked by SCAP; transported to golgi, cleaved by S1P (membrane protein) and S2P. high cholesterol -> cholesterol binds to SCAP and Insig

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21
Q

LXR-RXR

A

transcription factor that increases enzymes important for excreting cholesterol; increase bile salt formation; activates SREBP1
activated by high cholesterol

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22
Q

PCSK9 inhibitors

A

when used w statin massively increase LDLR

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23
Q

arachidonic acid

A

used by the body to synthesize 20C FA and 5member ring

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24
Q

how NH3+ travels in the blood

A

alanine, glutamate, glutamine

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25
Q

ALT

A

alanine amino acid transaminase (liver; if in the blood evidence of liver damage)

26
Q

enzyme defective in PKU

A

phenylalanine hydroxylase (phenylalanine to tyrosine; uses tetrahydrobiopterin and NDAH)

27
Q

toxic side product that accumulates PKU

A

phenylpyruvate (“substrate excess”)

28
Q

clinical presentation PKU

A

cognitive disorder
light color skin
mousey smell

29
Q

screening for PKU

A

guthrie test (bacterial growth in response to blood); urine; mass spec

30
Q

treatment for PKU

A

diet; KUVAN = tetrahydrobiopterin

31
Q

pneumonic for phenylalanine pathway

A

find yourself hiking high mountains for fun alone
(phenyalanine, tyrosine, hydroxyphenylpyruvate, homogentase, maleylacetoacetate, fumarylacetoacetate, fumarate+acetoacetyl-coA)

32
Q

tyrosinemia I

A

succinylacetone (from all the fumarylacetoacetate) acumulates. enzyme: fumarylacetoacetase. symptoms: liver failure, bilirubin, no coagulation factors, edema, anemia (heme producing protein blocked by succinylactone) blood tyrosine and methonine; succinyllactone in urine. treatment: NTBC = inhibitor of hydroxyphenylpyruvate dioxygenase

33
Q

MSUD

A

mitochondrial BCKD (branched chain keto acid dehydrogenase) is defective. keto acid derivative excreted in urine smells like maple syrup. pt is acidotic. AR. neuronal defects, ataxia, poorly responsive, coma, seizures; attacks brought on by other illnesses (catabolic activity turned on)

34
Q

homocystinuria

A

enzyme defective: CBS (homocysteine cannot be turned into cystathionine, precursor of cysteine). homocysteine and methionine accumulate. tall posture, scoliosis, learning abnormalities, clotting disorder –> strokes/infarctions; lens of eye dislocates. diagnosis: urine homocysteine sky high. diet

35
Q

diazoxide

A

inhibits K channel closure –> cell remains hyperpolarized –> Ca influx is inhibited –> insulin not released

36
Q

OTC deficiency

A

urea cycle defect
carbamoul phosphate generates orotic acid instead of citrulline
XR
presentation: lethargy, seizure; high NH3 levels. Note: steroids, trauma, weight loss –> can trigger excess NH3 and disease manifestation
treatment: dialysis; scavenger theraphy w benzoic acid or phenylbutyrate

37
Q

arginosuccinate lyase deficienty

A

urea cycle defect

38
Q

HSP 70, HSP60

A

heat proteins/chaperons - refold proteins inside mitochondria

39
Q

3 common “metabolite imbalances” in mitochondrial diseases

A
  1. high pyruvate
  2. high lactate
  3. NADH > NAD+
40
Q

mitochondrial complex encoded by nDNA

A

complex II (succinate dehydrogenase) –> part of the TCA cycle

41
Q

electron path in mitochondria

A

CoQ - III - cytochrome C - IV cytochrome oxidase (H2O is created here; cyanide sensitive step)

42
Q
  1. heteroplasty
  2. threshold effect
  3. mitotic segregation
A
  1. mitochondrial genes are different from one another
  2. pt is fine w up to 70-80% gene defect
  3. daughter cells might have more or less defective mitochondria
43
Q

kinesin

A

motor protein towards (+) = synapse

44
Q

dynein

A

motor protein away from synapse

45
Q

Miro and Milton

A 
adaptor proteins (GTPases). 
microtubule --> kinesin motor --> miro and milton --> mitochondria
46
Q

Charcot-Marie-Tooth

A

AD. mitochondrial protein Mfn2 (fusogenic protein in the outer membrane *works by dimerizing) defective. nDNA. long nerves affected – muscle weakness, gait disturbances. CMTI worse than CMTII

47
Q

Optic Atrophy Gene

A

AD. mitochondrial protein OPA1 (fusogenic protein in the inner membrane*works by dimerizing) defective. nDNA. vision loss, ophtalmoplegia

48
Q

protein involved in mitochondrial fission

A

dynamin

49
Q

ptosis

A

drooping eye lids

50
Q

Kerns-Searns (KSS)

A

mitochondrial disease
large deletion of mDNA and tRNA genes. muscle biopsy = ragged red fibers. cytochrome oxidase missing.
anemia (can disappear); ptosis; low weight

51
Q

NARP (Neuropahty Ataxia Reinitis Pigmentosa)

MILS (Maternal Inherited Leigh Syndrome)

A

2 mitochondrial diseases that can be caused by same mutation. heteroplasty results in phenotypic variations. NARP (70-90% mtDNA mutation). MILS (>90% mutation)

52
Q

MNGIE

A

mitochondrial disease. thymine phosphorylase defective –> thymidine accumulates –>imbalance of nucleosides –> mDNA instability and loss.
affects GI neurons –> diarrhea one of the first signs of disease

53
Q

Nucleic acid salvage pathway

A

Ribose-1-P=>ribose-5-P=>5-phosphoribosyl-1-pyrophosphate (PRPP). –> add new bases A and G and Hypoxanthine to reform the Purine Nucleotides

54
Q

De Novo nucleic acid pathway

A

start w adding NH3 to 5-PRPP. ring build w aa doming NH3 and multiple C donors (glycine, CO2, C=O ). Result: inosine monophosphate

55
Q

IMP

A

inosine monophosphate. product of de novo nuc acid synthesis. source of GMP (imp oxidized to xanthine, nitrosylated by glutamine) and AMP

56
Q

pyrimidine de novo pathway

A

create base first then ligate to sugar (vs. purine - build base at 5PRPP)

57
Q

gout

A

too much uric acid –> kidney stones, gouty arthritis. diagnosis: xray shadow, milky joint fluid. treatment; rasburicase (enzyme), allopurinol (competitor inhibitor that binds to xanthine oxidase)

58
Q

Lesh-Nyhan

A

X linked
defect in HGPRT (rescues hypoxanthine and guanine to produce GMP and IMP). way too much uric acid. gout, self mutilation, failure to walk, communicate. treatment: restrict aa consumption

59
Q

phosphoribosyl pyrophosphate synthetase superactivity

A

similar to Lesh-Nyhan - defect in enzyme causes gout, etc

60
Q

SCID

A

severe combined immunodeficiency: adenoside deaminase deficiency (adenosine –> inosine). adenosine accumulates and forms dATP -> inhibits proliferation of immune cells. repetitive infections. enzyme replacement, bone marrow transplant

61
Q

probenecid

A

drug for chronic treatment of gout; blocks transport of uric acid from kidney to blood

Molecular Mechanisms (3 decks)

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