Which enzyme is absent in Pompe’s disease?
-does it present w/hypoglycemia?
alpha-1,4-glucosidase (acid maltase).
-no it does not present w/hypoglycemia.
Fragile X syndrome
- defect affecting the ______ & expression of the _____ gene.
- inheritance pattern?
- methylation, FMR1.
- x-linked recessive.
Are Power and sample size related?
Yes, directly related.
-inc. sample size leads to inc. power of a study.
Why does hyponatremia (ie. from thiazides) lead to lithium toxicity?
B/c PCT will then try to resorb more Na and will resorb lithium as well bc of the similar structure. So you’ll be resorbing too much lithium.
-lithium has a narrow therapeutic index.
If splenic art is blocked, which arteries that come off of it have poor anastomoses?
- what does the T stand for?
- what are the main Sxs of esophageal dysmotility?
- what will barium study show of esophagus?
- heartburn, regurg, dysphagia.
- dilated esophagus & absent parastalsis
“corkscrew esophagus” seen in what disease?
diffuse esophageal spasm
-mechanism behind esophageal dysmotility?
fibrous replacement of muscularis.
Coronary steal syndrome
- what is the key?
- most often seen w/which drugs?
Key is that collaterals will form distal to the block, and the tissue fed by the blocked areas will be releasing vasodilators due to the ischemia.
-if you give a coronary vasodilator, now the other cornaries (in healthy parts) are also vasodilated, so more blood shunted to them and less blood to ischemic areas!
*seen w/coronary artery vasodilators - adenosine, dipyridamole.
Selective coronary artery vasodilators: name 2:
How many hours of fasting can glycogen stores last before they’re depleted?
12 to 18 hours.
-then gluconeo takes over.
- whats the most common cause?
- Tx for prevention?
Phenytoin and valproate inhibit intestinal absorption of which vitamin?
-can lead to what birth defects?
-can lead to neural tube defects.
-deriv of which aortic arch?
6th aortic arch.
- seen in what?
- what is it?
- constrictive pericarditis.
- ventricular compliance reduced via an external force.
- endothelial cells display what?
- neutros display what?
- sialyl lewis acid
-what will you see histologically?
mononuclear, parenchymal infiltration w/well-developed germinal centers.
Infection, pain, sleep deprivation.
- what will blood glucose levels be? inc or dec?
- therefore, will these precipitate a hypoglycemic state in a diabetic?
- typically due to catecholamine release.
- no they will not.
- will stimulate glycogenolysis & gluconeo.
- pt will return to consciousness in 10-15 min.
Purely ketogenic AAs:
Lysine and Leucine
-the onLy pureLy ketogenic amino acids.
- Ketogenic = producing acetoacetate or its precursors.
- Glucogenic = producing TCA intermediates or pyruvate
Inc. serum alanine starting in infancy.
- which disease?
-inc. intake of ketogenic nutrients (e.g., high fat content or inc. lysine and leucine).
Malate to OAA
- produces what?
- what happens in alcoholics?
- Malate to OAA = make NADH. So in alcoholics w/high NADH, opposite rx takes place, OAA => malate, producing NAD+.
- since you need OAA for gluconeo, this inhibits gluconeo, which is why alcoholics get resting hypoglycemia.
Tender loving care for nancy enzymes:
PDH, alpha-KG-DH, branched chain DH.
- these all req thiamine.
- transketolase ONLY req thiamine.
Substrate level phosphorylation steps:
Rotenone, cyanide, antimycin A, CO.
-how do they poison us?
Electron transport inhibitors.
-how does it poison us?
ATP synthase inhibitor.
- 2,4-Dinitrophenol (used illicitly for weight loss).
- aspirin (fevers often occur after aspirin overdose).
- thermogenin in brown fat.
Electron transport chain
- protons pumped into which part of the mito?
- where is the ADP made into ATP?
- intermembrane space.
- ATP made in mito matrix, the ATP synthase is in inner-mito membrane.
-where is this enzyme found?
-also kidney & intestinal epithelium.
- cofactor for which enzyme?
- action of enzyme?
- glutathione peroxidase which prevents oxidative damage by converting H2O2 → H2O.
- This is especially important in RBCs.
- whats it do?
- whats it need?
- NADPH oxidase oxidized NADPH and transfers those electrons to O2 to make a superoxide free radical.
- need NADPH for this.
what gives sputum its color?
-has green pigment.
G6PD def pts
- why will they be immunocompromised?
- relationship to CGD?
- G6PD def pts = will be immunosuppressed bc NADPH oxidase needs NADPH in order to make superoxide.
- dont confuse w/CGD which is a def. of the actual enzyme, NADPH oxidase.
Pyocyanin of P. aeruginosa
Pyocyanin of P. aeruginosa functions to generate ROS to kill competing microbes.
-what is it?
Lactoferrin is a protein found in secretory fluids and neutrophils that inhibits microbial growth via iron chelation.
-fructose appears in blood and urine.
- which enzyme deficient?
- whats the main problem?
- aldolase B.
- dec. in available phosphate, which results in inhibition of glycogenolysis and gluconeogenesis.
- hypoglycemia, jaundice, cirrhosis, vomiting.
* NO cataracts!
Can breastmilk induce fructose intolerance?
- breastmilk has lactose in it, not sucrose or fructose. So baby wont develop Sxs of this until he’s weened off breast milk and starts having sucrose or fructose in his diet!
Breast milk contains which sugars?
Lactose + maltose
- maltose = glucose + glucose
- Lactose = glucose + galactose
maltose = what sugars combined?
-maltose = glucose + glucose
lactose = what sugars combined?
-Lactose = glucose + galactose
- infantile cataracts.
- May initially present as failure to track objects or to develop a social smile.
-failure to thrive, jaundice, hepatomegaly, infantile cataracts, intellectual disability.
Can breastmilk induce galactosemia/galactokinase def?
- breastmilk contains lactose and maltose.
- lactose => glucose + galactose.
Cataracts in fructose or galactose metabolism problems?
- lens has curvy shape like your GUT.
- cataracts seen in galactose problems, not fructose.
What is converted to lactose via lactose synthase?
UDP galactose converted to lactose via lactose synthase.
galactosyl beta 1-4 glucose
Intestinal biopsy will show what in lactose intolerance?
Intestinal biopsy reveals normal mucosa in patients with hereditary lactose intolerance.
- pH of stool?
- hydrogen content of breath?
- dec. pH.
- inc. hydrogen content w/lactose tolerance test.
- colonic anaerobes will digest lactose and produce hydrogen gas.
- dec. pH of stool.
-what type of diarrhea?
methionine (Met), valine (Val), histidine (His).
-PVT TIM HALL
Which AAs are only essential during periods of growth?
Arg and His are required during periods of growth.
Which AAs are abundant in histones?
Arg and Lys.
CPS1: which cycle, location of enzyme?
CPS2: which cycle? location of enzyme?
- urea cycle, mitochondria.
- pyrimidine synth, cytosol.
- substrates in order:
Ordinarily, Careless Crappers Are Also Frivolous About Urination.
- carbamoyl phosphate
-what is formed in mito then leaves to cytoplasm?
citrulline formed in mito then leaves into cyto.
-carbamoyl phosphate + ornithine = citrulline.
______ transports ammonia from peripheral tissues to kidneys.
-Glutamine transports ammonia from peripheral tissues to kidneys.
Low BUN = ______ problem, not ______ enough.
High BUN = ______ problem, not ______ enough.
Low BUN = liver problem, not making enough.
High BUN = kidney problem, not excreting enough.
Does Urea change pH of blood?
- doesn’t change pH
- goes thru membranes
Which enzymes responsible for producing direct donors of nitrogen into Urea cycle?
CPS1 & aspartate aminotransferase.
aspartate aminotransferase = aspartate transaminase = AST = liver enzyme!
- lactic acid made by muscle goes into blood stream.
- From blood stream it gets taken up into liver.
- In liver, you convert lactic acid back to pyruvate. This done using same enzyme, LDH.
- LDH works both ways, Pyruvate lactic acid.
- pyruvate goes through gluconeo., gets converted to glucose, gets dumped into blood stream, and is picked back up by the muscle.
*after heavy exercise, you need about 1 hour to convert that lactic acid back to pyruvate.
- In muscle, pyruvate end product of glycolysis has an amino group added to it to make Alanine.
- this is helping muscle cells remove excess nitrogen from burning amino acids.
- Alanine dumped into blood, picked up by liver.
- alanine does NOT change pH of bloodstream like lactic acid.
- Liver will take amino group back off (sent to urea cycle), pyruvate used to make glucose, sent to blood stream, picked up by muscle, and thats the cycle.
*body prefers Cori cycle b/c cori cycle regenerates NAD+.
Name an example of an alpha-ketoacid
pyruvate! (pyruvic acid).
How does muscle send its ammonia to the liver?
-carried on what molecule?
1) the AAs it wants to burn (this is times of starvation) have their amino groups transferred to α-KG which becomes glutamate.
2) glutamate transfers its amino group to pyruvate. So glutamate transformed back to α-KG, and pyruvate transformed to alanine.
3) alanine transports the amino group in blood bc it wont change pH of blood.
4) alanine taken up in liver.
5) alanine transfers amino group back to α-KG to make glutamate. Alanine transforms back to pyruvate.
6) glutamate can transfer its amino group to OAA and make aspartate which will go to urea cycle.
*transaminases do these, req. B6.
OAA + NH3 =
α-KG + NH3 =
How do tissues other than muscle send ammonia to urea cycle?
- ammonia is put onto R-group of glutamate, now its called glutamine (not charged, wont raise blood pH).
- dumped into the blood and brought into the kidney.
- In kidney, ammonia removed from glutamine (forms glutamate again).
- ammonia picks up proton, becomes ammonium, and is excreted in urine.
- glutamine can also be sent to intestine, where its also converted back to glutamate and ammonia.
- ammonia dumped into portal circ and gets to liver (its okay to raise pH here cuz it’ll get to liver quickly).
- the ammonia in the liver will be one of two nitrogens that will end up on urea. UREA CYCLE.
glutamate + NH3 =
Hyperammonemia depletes ______, leading to inhibition of TCA cycle.
- limit protein in diet.
- Benzoate or phenylbutyrate = bind amino acid and lead to excretion.
- Lactulose to acidify the GI tract and trap NH4+ for excretion.
Benzoate or phenylbutyrate
- given for what?
- how do they work?
- bind amino acid and lead to excretion.
-what pathway and what effect?
N-acetylglutamate = obligate activator of CPS1 of urea cycle.
-results in hyperammonemia.
-what rxn does it catalyze?
carbamoyl phosphoate + ornithine = citrulline.
Ornithine transcarbamylase deficiency (OTC def.)
*vs. other urea cycle enzyme deficiencies, which are autosomal recessive
All urea cycle enzyme deficiencies are auto recessive except this one, which is x-linked recessive:
Ornithine transcarbamylase deficiency
Ornithine transcarbamylase deficiency (OTC def.)
- Excess carbamoyl phosphate spills out of mito and into cytoplasm is converted to orotic acid via CPS2 (part of the pyrimidine synthesis pathway).
- inc. orotic acid in blood and urine, dec. BUN, symptoms of hyperammonemia.
*No megaloblastic anemia (vs. orotic aciduria).
- do you get anemia?
- if so which kind? and how?
- same reason as folate/B12 def - dec. pyrimidine synthesis.
- Inability to convert orotic acid to UMP (de novo pyrimidine synthesis pathway) because of defect in UMP synthase.
DOPA => Dopamine
Dopamine => NE
NE => Epi
- which enzyme?
- which cofactor?
- cofactor = SAM
Phe => tyrosine
tyrosine => DOPA
Tryptophan => serotonin
Arginine => NO
Where does ketogenesis take place?
Venous drainage of adrenal cortex goes through what?
- cortisol therefore flushes thru adrenal medulla & inc. txn of PNMT enzyme which converts NE to epi.
- this is why adrenal medulla is 80% epi and 20% NE.
Inc. PRPP synthetase activity can lead to what joint problem?
-more purines made so more purines metabolized to uric acid.
Septic shock - why would you have high lactic acid levels?
- shock = hyptension = reduced delivery of O2 to tissues = anaerobic metabolism = lactic acidosis.
- hepatic hypoperfusion also contributes to build up of lactic acid as liver = site of lactate clearance.
homeobox genes usually code for what?
- whos got it?
- LCAT activation (cholesterol esterification).
- HDL & chylomicron.
chylomicron assembly & secretion by intestine.
- whos got it?
Binds LDL receptor.
-VLDL, IDL, LDL
apoB-100 on LDL is what binds the LDL receptor.
- Oxidation of apoB-100 is what leads to atheromas.
- each LDL only has 1 apoB-100 protein
- whos got it?
- Lipoprotein Lipase (LPL) cofactor.
- VLDL, chylomicron, HDL.
ApoE3 & E4
VLDL & chylomicron remnant uptake by liver.
- is its charge more or less negative than HbA?
- how about compared to HbC?
- HbS has a decreased negative charge bc you replaced glutamic acid (- charge) w/valine.
- that means it wont travel as fast toward the cathode bc its not as negative.
-HbC replaces glutamic acid w/lysine which has a (+) charge, so it’ll travel even less toward the cathode than HbA or HbS.
HbA HbS & HbC
-arrange in order of how negatively charged they are.
HbA = most neg. charge = travels fastest toward cathode.
HbC = most positively charge = travels slowest toward cathode.
Speed of movement on gel electrophores
-HbA, HbC, HbS
HbA > HbS > HbC
- HbA = most neg. charged.
- HbC = least neg. charged.
*they are moving toward a cathode.
UV radiation causes _____ dimer formation
-NOT purine dimers!
What kind of repair fixed pyrimidine dimers?
-what does it us?
NER using specific endonucleases.
Porphyria cutanea tarda
- which enzyme is deficient?
- what builds up?
In porphyria cutanae tarda & AIP where are the enzymes located?
Is there AA proofreading during translation?
- So if a tRNA charges up the wrong AA then that AA will be put in.
- it means the t-RNA synthetase proofreading didnt catch it when it loaded the AA.
Is myelofibrosis a myeloproliferative disorder?
yes - too many megakaryocytes releasing PDGF.
-tear drop cells.
-what is it?
-converts uric acid to allantoin.
-C/I in which pts?
pts w/bad renal function.
Why prescribe thaizides for nephrogenic DI?
nephrogenic DI: ADH channels not working. Can’t resorb any free water.
-thiazides prevent NaCl resorption in DCT, so this water is no longer free. And can be resorbed by Aldo effect in beginning of collecting duct.
- 2 potential causes?
- which AA becomes essential?
- dec. phenylalanine hydroxylase.
- dec. tetrahydrobiopterin cofactor (malignant PKU).
-tyrosine becomes essential.
Max Myers has PKU: intellectual disability, fidgety (seizures), fair skin, blue eyes, musty odor, eczema.
- lack of melanin => fair skin.
- high Phe levels = neurotoxic.
- what AA becomes essential?
-tyrosine => DOPA also req BH4.
-when are these kids screened?
Screened for 2–3 days after birth (normal at birth because of maternal enzyme during fetal life).
-what do you find in urine?
Which pts should avoid artificial sweetener?
PKU patients must avoid the artificial sweetener aspartame, which contains phenylalanine.
-whats the key Sx here?
Urine turns black on prolonged air exposure.
-whats the problem here?
Congenital deficiency of homogentisate oxidase in the degradative pathway of tyrosine to fumarate.
- dark connective tissue, brown pigmented sclerae, urine turns black on prolonged exposure to air.
- May have debilitating arthralgias (homogentisic acid toxic to cartilage).
- ochronosis = darkening of cartilage.
- ear cartilage = common place that gets pigmented.
-besides homocysteine methyltransferase w/B12, what other enzyme works on this and whats its cofactor?
Cystathionine synthase w/B6.
Homocystinuria: Cystathionine synthase deficiency
- dec. methionine (bc homocysteine gets shunted toward making methionine).
- inc. cysteine (bc you wont be making it).
- inc B12 & folate in diet.
Homocysteine methyltransferase deficiency
inc. methionine in diet.
Homocystinuria: all causes
- inc. homocysteine in urine, intellectual disability, osteoporosis, tall stature, kyphosis, lens subluxation (downward and inward), thrombosis, and atherosclerosis (stroke and MI).
- marfanoid habitus w/clotting & thrombosis issues.
-whats the problem?
Hereditary defect of renal PCT and intestinal AA transporter for Cysteine, Ornithine, Lysine, and Arginine (COLA).
-how to Dx?
Urinary cyanide-nitroprusside test is diagnostic.
-urinary alkalinization (e.g., potassium citrate, acetazolamide).
Maple syrup urine disease
-which AA will be found most in the blood?
Leucine the most.
-also isoleucine & valine, but not as much.
- whats the odor?
- what has the odor? the child? his urine?
-The child has this odor, not his urine.
*as opposed to MSUD where the urine smells like maple syrup.
Causes severe CNS defects, intellectual disability, and death.
Restriction of leucine, isoleucine, and valine in diet, and thiamine supplementation.
- what does it do?
- which enzyme activates it?
- breaks down collagen.
- Glycogen phosphorylase kinase activates it.
Glycogen phosphorylase kinase
- does it activate or inhibit glycogen phosphorylase?
- what activates it?
- activate => glycogen breakdown.
- Ca, PKA (glucagon & epi).
-which enzyme inhibits it?
- does it activate or inhibit Glycogen phosphorylase?
- what activates it?
- inhibits it.
How is glycogen degradation coupled w/skeletal muscle contraction/exercise?
Calcium released from SR during muscle contraction activates glycogen phosphorylase kinase which activates glycogen phosphorylase which breaks down glycogen!
why even make glycogen? why not just store glucose?
b/c its way less osmotically active than having a bunch of glucose stored.
How long can you exercise before glycogen runs out?
frequent oral glucose/cornstarch; avoidance of fructose and galactose.
- which enzyme deficient?
- why isn’t it as bad as Von Gierke’s?
- Debranching enzyme (α-1,6-glucosidase).
- Gluconeogenesis is still intact.
-what will you see inside hepatocytes?
-small chain dextrin-like material build up in cytosol of
Blood lactate levels
- Von Gierkes?
- Von Gierkes = inc. blood lactate.
- Cori = normal lactate levels.
-which enzyme is deficient?
Skeletal muscle glycogen phosphorylase (myophosphorylase)
-how can it lead to arrythmia?
- muscle lysis means more potassium in the blood stream.
* lack of glucose means lack of ATP which means muscle cells can lyse giving rise to a myoglobinuria.
-when does it set in?
Adolescence or early adulthood.
Long chain FAs
-how do they get into mitochondria to be metabolized?
- what is it?
- whats it cause?
- inability to transport LCFAs into the mitochondria, resulting in toxic accumulation.
- Causes weakness, hypotonia, and hypoketotic hypoglycemia.
- if you can’t burn fat, you cant do gluconeogenesis.
- what is it?
- how does numbering go?
Omega carbon = last carbon = methyl carbon of FA.
-relative to the last carbon (omega carbon), where do you find the first double bond? If its 3 before last carbon = omega 3 FA.
-where in the cell?
-from citrate that overflowed when isocitrate DH was inhibited by neg. feedback.
Acetyl CoA => malonyl CoA
- 2nd step in what pathway?
- whats the enzyme that does this?
- what cofactors does enzyme need?
- what activates the enzyme?
- FA synthesis in cytoplasm.
- acetyl-coa carboxylase (ABC carboxylase)
- needs ATP, biotin, & CO2.
- insulin activates this enzyme.
*When there is no insulin (DM1) or during starvation, epi/glucagon inhibit FA synthesis. This shunts acetyl-coa toward ketone production.
Citrate => acetyl-CoA + OAA
- 1st step in which pathway?
- whats the enzyme?
- FA synthesis in cytoplasm (after citrate spilled over from mito).
- ATP citrate lyase
ATP citrate lyase
- how do we remember this is for FA synthesis?
“SYtrate” = SYnthesis.
Hormone Sensitive Lipase
- what turns it on?
- what does it do?
- breaks down TGs into FAs + glycerol.
*remember, cortisol & glucagon turn on gluconeo, turn on PEP carboxykinase.
- what is it?
- what does it taken where?
Takes acyl-coa (FA + CoA) from cytoplasm into the mitochondria so it can undergo beta-oxidation.
Fatty Acid + CoA => acyl-coa
- 1st step of what pathyway?
- whats the enzyme?
- where does this take place?
- FA beta-oxidation
- Fatty acid CoA synthetase
Fatty acid CoA synthetase
-1st enzyme of which pathway?
- Fatty Acid + CoA => acyl-coa
- acyl-coa can go into carnitine shuttle and enter mitochondria which is where beta-oxidation takes place.
What inhibits the carnitine shuttle?
-why does this make sense?
*Keep in mind, the FAs made in the cytoplasm in FA synthesis are not entering back. This is b/c malonyl CoA
inhibits Carnitine shuttle. Malonyl CoA is a product of FA synthesis. So this is basically a signal telling your
body not to burn the FAs that you just made.
Fatty acyl CoA dehydrogenase
- turns what pathway off?
- turns what pathway on?
- turn off PDH (glycolysis)
- turn on pyruvate carboxylase (gluconeo).
Why does alcoholism promote ketone production?
bc the inc NADH shunts OAA to malate. And once OAA runs out is when you start making ketones.
Where are ketones made?
-which organ & which compartment of cell?
Exclusively in the liver.
Acetyl-CoA from FA beta-oxid
- what are its 2 possible paths?
- what determines which path it takes?
Krebs and ketone synth.
-determined by if there is OAA available.
-acetyl coa accumulated in mitochondria b/c lack
of OAA. Its all channeled to ketone body formation.
Why is ketone production made in the specific organ that its made in?
Liver can NOT utilize ketone bodies b/c lacks enzyme thiophorase.
Why is the liver unique in its ability to make ketones?
-OAA gets depleted in liver b/c gluconeo. Extra-hepatic
cells do NOT do gluconeo! Only liver does!
-This is why OAA is present in these other cells so it can combine w/acetyl coa of the ketone to make citrate and enter the TCA cycle.
*acetoacetate (ketone body) converted to 2 acetyl-coa once in its target cell.
What is the ketone body broken down into once its in its target cell?
- where in the cell does this happen?
- which cell can not use ketones?
- you get 2 acetyl-coas for every b-hydroxybutyrate.
- happens in mito.
- RBCs dont have mitos, so can not use ketones!
Why can’t RBCs use ketones?
Ketone breakdown to 2 acetyl-coas happens in the mitochondria. RBCs dont have mitochondria.
Which is the dominant ketone body?
acetoacetate = unstable molecule, converted to beta-hydroxybutryate.
-can also spont. decarboxylate to acetone (which is not used for fuel).
*acetone can not be used as fuel, cant get ATP from it.
Urine test for ketones does not detect _____.
-rate limiting enzyme?
1 g protein or carbohydrate = ___ kcal.
1 g protein or carbohydrate = 4 kcal.
1 g fat = ____ kcal.
1 g fat = 9 kcal.
1 g alcohol = ____ kcal.
1 g alcohol = 7 kcal.
After how many days of starvation do ketones become main fuel for brain?
after 3 days of starvation.
-converts HMG-CoA to what?
lipoprotein lipase (LPL)
- where is it found?
- triggered by what hormone?
- vascular endothelial surface.
esterification of cholesterol =
-which enzyme does this?
putting a FA onto the -OH of cholesterol.
- makes it more hydrophobic.
- LCAT (needs apoA).
Cholesterol ester transfer protein (CETP)
-what does this do?
Mediates transfer of cholesterol esters to other
-mostly TGs or cholesterol?
Chylomicrons are mostly TGs. Milligrams of TGs, micrograms of cholesterol.
Oxidation of what apolipoprotein leads to atheroma formation?
Oxidation of apoB-100 is what leads to atheromas.
-each LDL only has 1 apoB-100 protein.
- Need B-100 for LDL to bind LDL receptor on liver. If it doesn’t it stays in blood.
- This is why oxidized LDL is the “bad cholesterol”.
Out of the lipoproteins, which ones carry the most cholesterol?
LDL & HDL.
-what happens to it?
Macrophages attack and phagocytose the oxidized LDL (once B-100 is oxidized, the LDL looks foreign to body so macros attack it).
- Remember, cholesterol can not be broken down.
- Macrophage will continue to phagocytose LDL and bring in more and more cholesterol gets into subendothelium, and converted to foam cell.
- Foam cell will die, and components will spill out. The cholesterol is insoluble in blood. It will precipitate out. This is beginning of an atheroma.
- HDL can come by and big up cholesterol thats been precipitated and b/c it has ApoA, it can signal LCAT to come esterify it, then pass it to IDL, which becomes LDL and can get back to normal cells/liver.
- HDL can also itself bind to receptors on the liver. Reverse cholesterol transport.
- where is it secrete from?
- does alcohol inc or dec. its synthesis?
- Secreted from both liver and intestine.
- Alcohol inc. synthesis of HDL.