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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
ALT
alanine amino acid transaminase (liver; if in the blood evidence of liver damage)
26
enzyme defective in PKU
phenylalanine hydroxylase (phenylalanine to tyrosine; uses tetrahydrobiopterin and NDAH)
27
toxic side product that accumulates PKU
phenylpyruvate ("substrate excess")
28
clinical presentation PKU
cognitive disorder light color skin mousey smell
29
screening for PKU
guthrie test (bacterial growth in response to blood); urine; mass spec
30
treatment for PKU
diet; KUVAN = tetrahydrobiopterin
31
pneumonic for phenylalanine pathway
find yourself hiking high mountains for fun alone (phenyalanine, tyrosine, hydroxyphenylpyruvate, homogentase, maleylacetoacetate, fumarylacetoacetate, fumarate+acetoacetyl-coA)
32
tyrosinemia I
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
MSUD
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
homocystinuria
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
diazoxide
inhibits K channel closure --> cell remains hyperpolarized --> Ca influx is inhibited --> insulin not released
36
OTC deficiency
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
arginosuccinate lyase deficienty
urea cycle defect
38
HSP 70, HSP60
heat proteins/chaperons - refold proteins inside mitochondria
39
3 common "metabolite imbalances" in mitochondrial diseases
1. high pyruvate 2. high lactate 3. NADH > NAD+
40
mitochondrial complex encoded by nDNA
complex II (succinate dehydrogenase) --> part of the TCA cycle
41
electron path in mitochondria
CoQ - III - cytochrome C - IV cytochrome oxidase (H2O is created here; cyanide sensitive step)
42
1. heteroplasty 2. threshold effect 3. mitotic segregation
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
kinesin
motor protein towards (+) = synapse
44
dynein
motor protein away from synapse
45
Miro and Milton
``` adaptor proteins (GTPases). microtubule --> kinesin motor --> miro and milton --> mitochondria ```
46
Charcot-Marie-Tooth
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
Optic Atrophy Gene
AD. mitochondrial protein OPA1 (fusogenic protein in the inner membrane*works by dimerizing) defective. nDNA. vision loss, ophtalmoplegia
48
protein involved in mitochondrial fission
dynamin
49
ptosis
drooping eye lids
50
Kerns-Searns (KSS)
mitochondrial disease large deletion of mDNA and tRNA genes. muscle biopsy = ragged red fibers. cytochrome oxidase missing. anemia (can disappear); ptosis; low weight
51
NARP (Neuropahty Ataxia Reinitis Pigmentosa) | MILS (Maternal Inherited Leigh Syndrome)
2 mitochondrial diseases that can be caused by same mutation. heteroplasty results in phenotypic variations. NARP (70-90% mtDNA mutation). MILS (>90% mutation)
52
MNGIE
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
Nucleic acid salvage pathway
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
De Novo nucleic acid pathway
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
IMP
inosine monophosphate. product of de novo nuc acid synthesis. source of GMP (imp oxidized to xanthine, nitrosylated by glutamine) and AMP
56
pyrimidine de novo pathway
create base first then ligate to sugar (vs. purine - build base at 5PRPP)
57
gout
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
Lesh-Nyhan
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
phosphoribosyl pyrophosphate synthetase superactivity
similar to Lesh-Nyhan - defect in enzyme causes gout, etc
60
SCID
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
probenecid
drug for chronic treatment of gout; blocks transport of uric acid from kidney to blood

Molecular Mechanisms (3 decks)

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