Biochemistry UWorld and other

jdlevenson's version from 2015-05-09 02:44


Question Answer
Why do alcoholics have fatty liver?Ethanol makes FA, TG etc but it also inhibits TG -> Adipose via VLDL so TG stay in liver!! Reversible at first.
What is required to make FA?NADPH, Acetyl CoA, C02, ATP
How is glycerol made?Glucose -> glycolysis -> DHAP -> Glycerol 3p.
Insulin and VLDLInsulin turns on lipoprotein lipase to break down VLDL to deposit TG in adipocyte for storage
TG vs Glycogen and waterTG – anhydrous; no water/ non polar. Adipocyte is 90% anhydrous. Glycogen – hydrous. Body can make only a limited supply.
Transient hypercholesterolemia4-5 hours post feeding cholesterol and TG will be high in blood.
Chylomicron hasCholesterol Ester, TG, Phospholipid and ApoB-48.
ACATOnce Cholesterol and FA absorbed in lumen, ACAT puts FA on cholesterol to make Cholesterol Ester where it can then form small part of chylomicron.
Chylomicron, how is it made and what functionMade in intestinal mucosal villi. TG broken down into FA and MG in lumen. Absorbed and reform TG. Then, in enterocyte, Chylomicron combines TG with PL, CE and ApoB48 and is then secreted into lymph. It transports TG to peripheral tissues.
AbetalipoproteinemiaDefect in Apo-B-48; decrease in serum TG and cholesterol because chylomicron cannot be made properly.
Chylomicron bumps into HDL in lymph and donates ApoC and ApoE to chylomicron that already has B48. What for?ApoE and C take chylomicron to adipose where LipoProtein Lipase breaks it down and absorbs FA. ApoC returns to HDL and then chylmicron remnant is left with ApoE and ApoB48.
All dietary TG goes to ? whereas all dietary cholesterol goes to ?Cholesterol-> Liver. TG -> Adipocytes.
Type II Familail HypercholesterolemiaAbsent or defective LDL receptors. Lots of cholesterol in blood and Liver keeps making more because it is not seeing any.
GallstonesToo much cholesterol and not enough bile salts in bile.
Acute hemorrhagic pancreatitisAccumulation of stones in ampulla of vater.
High TG a/wPancreatitis more than Atherosclerosis.
When LDL in blood, if free radicals knock off ApoB100, then...Recognized as foreign by macrophages. Make oxidized LDL. Will dock with Macrophage scavenger receptor/ SRA. Breaks LDL into components and cholesterol now inside macrophages as foam cell that sits in subendothelium. Inside components of macrophage spill out since it can no longer fill its function and cholesterol precipitates since insoluble -> Atherosclerotic Plaque.
HDL has ApoA that willActivate LCAT. C-> CE. HDL then gives CE to IDL -> LDL. HDL SCAVENGES FREE PRECIPITATED CHOLESTEROL released from FOAM CELLS and USING LCAT -> IDL -> LDL brings it back to LDL that lost it or to liver via liver SR-B1, scavenger receptor
When increase cholesterol in cells/ liverDecreased HMG CoA reducatase. No synthesis. Increased ACAT for more storage. Decrease LDL receptor so no uptake.
When less cholesterol in cells/ liverIncreased HMG CoA reductase for more synthesis, increase LDL receptors for more uptake, decreased ACAT so none will be stoed.
Three fates of IDL1. Liver, recognized by B100, 2. HDL transfers CE to LDL in exchange for TG and PL, 3. LDL. If it loses ApoE
IDL ->picks up CE from HDL or goes to liver to be taken up with its ApoE or it loses ApoE and becomes LDL which then still delivers cholesterol to periphery.


Question Answer
KetogenicLeucine Lysine (K-> L)
GlucogenicValine Methionine Histidine
Ketogenic and GlucogenicTTIP
Transaminases requireB6
Hartnup Disasedefective transport in intestine and kidney of large neutral amino acids, especially TRP. Since TRP -> Niacin -> Pellagra LIKE symptoms, D, D, and D
Question Answer
Na/ AA symporter vs Na/ Gluc symporter?Na/ AA symporter also requires energy from sodium gradient but unlike gluc, symporter can take dipeptides and tripeptides directly across mucosa
Cystinuria1:7,000; somewhat common
CystnuriaDefective transport in kidney and intestine of BASIC AA (Lys, Arg)
Cys not absorbed makes CYSTINE -> relatively insoluble in water-> UTI and Renal Stones
Question Answer
Cystinuria treatmentLow protein diet and Acetazolamide which will increase pH of urine
Negative nitrogen balance?Infection, starvation, DM, dietary deficiency of any amino acid that is essential, protein malnutrition (kwashiorkor)
MarasmusDeficiency in number of calories
GlutamineMajor transport form of NH3/ ammonia that comes from Adenine Deaminase as well as Amino Acid metabolism
NH3 -> Glutamine -> 2 places?Kidney where it will be excreted as NH3 or to intestines -> portal as NH3 -> liver -> + asparatate and urea cycle -> UREA -> blood and then to kidney.
Urea has 2 nitrogens, 1 from and 1 from1 from Aspartate and 1 from NH3, itself either from Glutamate (via Alanine and muscle) or Glutamine (via tissue -> intestine -> portal -> liver).
In most tissues, where does NH3 goTo Glutamine
In liver, where does glutamate get its amino groups fromAmino acid metabolism OR Alanine, which is from Muscle via Cahill Cycle
Why does Muscle transport its amino group in AlanineAlanine is neutral and will not change pH of blood whereas if it was as Glutamate, it would make blood more acidic.
Carbamoyl Phosphate Synthetase I vs III is first step in Urea Cycle (within Mito Matrix) vs II is key for pyrimidine synthesis (from glutamine -> -> orotic acid)
Carbamoyl Phosphate Synthetase I is turned on byN acetylglutamate (and high protein meal)
Two obligate activators in body (vs allosteric activators)Acetyl CoA for PC in Gluconeogenesis and N-Acetylglutamate for Carbamoyl Phopsphate Synthetase I
Arginine not essential amino acid except forChildren, Pregnant women; those in positive nitrogen balance. Arginine needed to make histones for DNA.
2 key enzymes of Urea CycleCarbamoyl Phosphate Synthetase I and Ornithine Transcarbamoylase (which splits off Ornithine and Citrulline).
Very low BUNproblem with liver, such as cirrhosis or enzyme deficiency
Very high BUNproblem with kidney; possibly Pre-Renal Azotemia
Carb. Phos. Synthetase deficiencyHigh NH4+/ hyperammonemia; High Glutamine in blood; Low BUN; NO OROTIC ACIDURIA; AR*; cerebral edema, lethargy, convulsions, coma, death.
Ornithine Transcarb DeficiencyHigh NH4+/ hyperammonemia; High Glutamine in blood; Low BUN; YES OROTIC ACIDURIA; XL*; cerebral edema, lethargy, convulsions, coma, death. Why? Carb. Phos. Builds up, spills in blood, ends up entering pyrimidine synthesis and so you have a lot of CUT and a lot of its precursor Orotic Acid.
Brown tea colored urineHyperbilirubinemia
Pink red urinePorphyria
Dark blue black urineAlcaptonuria
Alcaptonuria, what enzyme is deficientHomogentinsic Oxidase. Homogentinsic Acid builds up.
AlcaptonuriaDark urine, onchonosis (darkening of cartilage), arthritis. RARE.
PKU treatmentLow Phe, avoid aspartame (diet coke diet pepsi)
PKU clinicalmental retardation, musty mousy odor, microcephaly
PKU is from what enzyme deficiencyPheHydroxylase OR THB
TLCFN reactionsPDH, AlphaKetoacid Deh, AlphaKG Dehydrogenase
Valine and Isoleucine go on to makePropionyl coA -> Scucinyl coA
B12 needed to makeSuccinyl CoA from Methylmalonyl CoA
Maple Syrup Urine DiseaseMaple syrup urine, mental retardation, abnormal muscle tone, ketosis
Methylmalonic AciduriaDefective Methylmalonyl coA Mutase OR B12 deficiency. Methylmalonyl Acid builds up from Methylmalonyl coA.