Lightbody Lecture 12 Flashcards Preview

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Flashcards in Lightbody Lecture 12 Deck (37):

E stores in typical body

135000kcal fats (85% of body's stored E), 24000kcal prot, 720kcal glycogen, 80kcal blood glucose (gluc can last 1 day)


beta oxidation

ox of FAs; takes place in mito matrix; FAs broken down into 2C frags (aCoA) which enter TCA or conv to ketone bodies in liver


ATGL - adipocyte TAG lipase

hydrolyzes only TAG


HSL - hormone sensitive lipase

hydrolyzes TAG and DAG; + by isoproteronol (stims adren receps), + by phos by PKA and PKG (translocates from cyto to perilipin-cont droplets, - by insulin)


MGL - monoglyceride lipase

hydrolyzes only MAG


acyl CoA synthetase

takes R-COO- FA and ATP, becomes acyl-adenylate intermed, then use again w/CoASH to become acyl-CoA + AMP


key process in fat metab

hydrolytic cleavage of stored TAG w/gen of FA and glycerol and their release from adipocytes where they're transported, complexed w/albumin, to various tissues to be used as E



coats lipid droplets in adipocytes; acts as protective coating agst lipases; non-phos (coats lipid droplet) or phos (by PKA and PKG, changes conf, exposing stored lipids to HSL)


carnitine acyltransferase I

in carnitine shuttle; - by malonyl CoA, makes O-acylcarnitine from L-carnitine, then O-acylcarnitine gets translocated and acyls transferred to move L-carnitine into cell


FA activation

after leave adipocytes, transported (att to albumin) to other tissue (m, heart, liver); short and med chain (<12) can x mito memb, activated in matrix; long (12-20) activ at outer mito memb, transported into mito by carnitine shuttle



dehydrogenase w/FAD as e- acceptor, then hydration, then dehydrogenase w/NAD as e- acceptor, then cleave CC bond (thiolase)-->acetyl-CoA and new fatty acyl-CoA w/2 fewer C units


b-oxid of palmitic acid (C16)

7 cycles; 131-2 = 129 ATP from activation; in mito matrix


2 mito systems of b oxidation

1) fam of memb-bd enz's spec for long-chain FAs; 2) soluble enz's in matrix spec for short and med chain FAs; as long shortens, moves from memb-bd complex to soluble matrix enz's (maj of FAs entering mito are long-chain)


metab of odd-chain FAs



oxid of unsat FAs

almost all unsat FAs cont only cis DBs; hydratase acts only on trans, so need isomerase (oleoyl-CoA; eventually become acetyl-CoA, but need an isomerase to make cis-->trans, then use hydratase


carnitine cycle mito fat oxid disorders

involves LCFA transport thru inner mito memb


disorders of mito fat oxid in general lead to

cardiomyopathy, hypoglycemia, hypokeosis, myopathy, encephalopathy; defs in carnitine cycle or inner memb can be partially overcome by giving MCFA or SCFA (milk)


inner memb sys mito fat oxid disorders

mainly shortening of LCFAs thru b-oxid


mito matrix fat oxid disorders

oxids FAs of shorter length, doesn't involve carnitine


artificially induced trans fatty acids

hydrogenate polyunsat cis oils-->bonds that don't reduce change from cis to trans (margarines) - not oxidized easily, so reduce rancidity, inc shelf life; cont no animal fats; raise LDL, lower HDL; contrib to coron heart dis, cancer, diab, obesity, liver dysfxn


ketone bodies

FAs metab to acetyl-CoA by b-ox, then condense to form KBs; synth ONLY in liver mito; secreted into blood, transported to other tissue (heart, m, kidney, brain), reconv to acetyl-CoA, used as E; liver cannot metabolize them!; synth small quant all the time, but in starvation, unctrl'd diab I synth in lg quants


synth of ketone bodies

acetyl-CoA-->acetoacetylCoA-->3-hydroxy-3-methylglutaryl-CoA (HMG-CoA--also in chol synth)-->acetoacetate-->acetone + b-hydroxybutarate


metab of ketone bodies

water sol equiv of FAs; brain can use in starvation



needed to metab KBs; liver deficient in this, so can only synth, not metab!


fasting, starvation, severe T1D

OAA (via malate) leaves mito, used for glucose synth (GNG)-->shuts down TCA; at time, liver prod A-CoA by b-ox of FAs, but has nowhere to go, so condenses to KBs; glc levels maint by glycerol, RBC lactate, AA brkdn (major source)


KB utilization

rel into systemic blood (acetone elim in urine, exhaled; acetoacetate and b-hydroxybutarate used as fuels); convert to E (b-hydroxybut and acetoacetate conv to acetoacetyl CoA using succ CoA from TCA; cleaved to 2-acetyl-CoA); range of tissues can use (brain when starved, thiophorase induced after 4d of starvation, derive 50% of E from KB); excess-->acidosis, relieved thru elim of KBs thru urine



high fat, low carbs-->fat mobil and KBs in urine; active fat metab and GNG; check for KB in urine-->sign that fat metab; discouraged b/c metabolic acidosis


KBs and T1D

diab-->high glc in blood; transport into tissues reduced; resp by inc GNG in liver, inc TAG brkdn in adipocytes; FAs transp to liver for ox, consuming most of OAA; no OAA, so excess a-CoA condenses-->KBs (detect acetone on breath)



synth bile acids, lipids, H peroxide, detox; live a few days; brkdn VLCFAs (C22-30), both sat and unsat; cont all b-oxid enz's (enz that activates VLCFA (acylCoA synthetase) only in this organelle); have sep transporter, so don't need carnitine; b-oxid only goes a few cycles, then rel'd to mito for further oxid



degrades H2O2 in peroxisome; 2H2O2-->2H2O + O2; don't prod ATP


FADH2 in peroxisome

gen'd by b-oxid; reox-->H peroxide; difers from mito where this enters e-transport chain (FADH2 + O2 --> FAD + H2O2)


NADH formed in peroxisome

can't be reox here, so has to be exported out


A-CoA formed in peroxisome

must transfer out b/c TCA cycle enz's absent



dec in abil for peroxisomes to degrade VLCFAs, so build up in adrenal, brain, plasma, fibroblasts-->interfere w/abil of adrenal to conv chol into steroid, demyelin nn in brain; appear @4-10yo (behav /\, bad vision, hearing, coord); death 2-4y later


X-ALD defect

ATP bdg ABCD1 transporter prot (ALDP), crucial for transport of VLCFAs into peroxisomes; treat w/Lor oil or stem cell therapy


Lorenzo's Oil

4:1 mix of oleic acid and erucic acid from olive and rapeseed oil; must give before symps present, low fat diet; retard disease (maj of VLCFAs accum are sat FAs from diet and synth)



synth saturated VLCFAs; elongates both sat and unsat FAs; monounsat FAs compete for this enz, lowering synth of sat VLCFAs