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98 Cards in this Set
- Front
- Back
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how much glucose does the brain and nervous system require per day under resting conditions
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150 g
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where are triacylglyerols of chylomicrons made
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intestinal epithelial cells
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where are triacylglyerols of VLDLs made
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liver
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what is the human ability to store fat
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limited by only the amount of tissue we can carry without overloading the heart
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gynecoid pattern
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breasts, hips and waist fat distribution
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android pattern
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apple; abdomen and upper body fat distribution
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syndrome X
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abdominal obestiry, hyperglycemia, hyperlipidemia, and high BP
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ketone bodies produced by the liver from fatty acids
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acetoacetate and B-hydroxybutyrate; liver can't use them as fuel
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length of very long chain fatty acids, long-chain fatty acids, medium-chain fatty acids, and short-chain fatty acids
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>20; 12-20; 6-12; 4
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what pathway do fatty acids produce ATP
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B-oxidation
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what transports activated acyl groups into mitochondrial matrix
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carnitine
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where does metabolism of water-soluble medium-chain fatty acids occur
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in the liver; doesn't require carnitine
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what happens to odd chain fatty acids when degraded down to propionyl CoA
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enters TCA cycle as succinyl CoA
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liver transaminases measured in the blood
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AST (aka SGOT), ALT (aka SGPT)
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AST
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aspartate aminotransferase; donates nitrogen to alpha-ketoglutarate forming oxaloacetate and alpha-ketoacid to aspartate
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ALT
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alanine aminotransferase; donates N to alpha-ketoglutarate forming pyruvate and glutamate
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what is the significance of elevated liver transaminases
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reflects damage of liver cell plasma membrane
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what do transaminases do
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catalyze transfer of the nitrogen group of an aa to an acceptor alpha-ketoacid
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how much energy is derived from oxidation of fatty acids after overnight fasting
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60-70%
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major fatty acids oxidized (long-chain)
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palmitate (C16), oleaate (C18:1), and stearate (C18) - highest in dietary lipids and synthesized in humans
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what happens to acetyl CoA produced from fatty acid oxidation
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principally oxidized in the TCA cycle or converted to ketone bodies in the liver
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fat percent in the american diet
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38%; 95% are triacylglycerols
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where are medium-chain length fatty acids present in the diet
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dairy fat, maternal milk, and vegetable oils
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animal fat constituents
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saturated and monounsaturated ling-chain fatty acids
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vegetable oil fats
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linoleate and some longer-chain and polyunsaturated fatty acids
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what does the pathway of fatty acid synthesis produce
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palmitate (C16) - can be elongated to stearate or unsaturated to form oleate
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why are long-chain fatty acids toxic to cells
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disrupt hydrophobic binding btwn aa side chains in proteins
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what must fatty acids be activated to before participating in B-oxidation and other metabolic pathways
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acyl CoA
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where is acyl CoA synthase located in the cell
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ER, outer mitochondrial membranes, and peroxisomal membranes; acts on C12-20
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where is the synthase located for very long chain fatty acids
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peroxisomes
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where is the synthase located for medium-chain fatty acids
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mitochondrial matrix of liver and kidney cells
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what occurs when B-oxidation is blocked due to inherited enzyme deficiency or metabolic regulation
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excess fatty acids diverted into triacylglycerol synthesis
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what is the fate of fatty acids with the synthase in the ER
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triacylglycerol and phospholipid synthesis
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what is the fate of fatty acids with the synthase in peroxisomes
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oxidation and plasmalogen synthesis
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what is the fate of fatty acids with the synthase in mitochondria
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B-oxidation
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What occurs to fatty acids that are not being used for energy generation in the liver and some other tissues
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reincorporated into triacylglycerols (re-esterified)
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Classical CPT II deficiency (carnitine:acyl-carnitine translocase)
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adolescent to adult onset of recurrent episodes of acute myoglobinuria precipitated by prolonged exercising or fasting - weak, hypoglycemic
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CPTII deficiency findings in infants
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hypoglycemia and hypoketosis are severe, hepatomegaly from triacylglycerol depoits, cardiomyopathy
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Carnitine:palmitoyltransferase I (CPTI)
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enzyme that transfers long-chain fatty acyl groups from CoA to carnitine; located on outer mitochondrial matrix
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how is carnitine obtained
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from diet or synthesized from side chain of lysine (begins in muscle, ends in liver)
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what is required to synthesize carnitine
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SAM to donate methyl groups, vit C
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where is most of the carnitine stored
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skeletal muscle - have high affinity uptake
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fatty acidsconversion to acetyl CoA produce what in the B-oxidation spiral
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FAD(2H) and NADH conserve energy and are oxidized in the Electron transport chain
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what happens to acetyl CoA after being produced from fatty acids
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oxidized in TCA cycle or converted to ketone bodies
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where has carnitine deficiency been found
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infants fed a soy-based formula not supplemented with carnitine
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riboflavin
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vitamin precursor of FAD which is required for acyl CoA dehydrogenases and ETFs
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CoQ
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synthesized in the body, but is the recipient in the ETC for electrons passed from complexes I and II and the ETFs
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pantothenate
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precursor of CoA; may improve performance
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where does cleavage of fatty acids begin
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carbozyl end attached to CoA
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what occurs before fatty acid cleavage
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B-carbon is oxidized to a keto group in two rxns (generate NADH and FAD2H)
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B-oxidation step 1
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double bond (trans) is formed btwn B and A-carbons by an acyl CoA dehydrogenase that transfers electrons to FAD
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B-oxidation step 2
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OH from water is added to B-carbon and an -H from water is added to the a-carbon (enoyl hydratase)
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B-oxidation step 3
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hydroxyl group on B-carbon is oxidized to a ketone by hydroxyacyl CoA dehydrogenase; NAD+ to NADH
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B-oxidation step 4
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bond btwn B and A-carbons is cleaved by rxn that attaches CoASH to the B-carbon and acetyl CoA is released; thiolytic rxn
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B-oxidation vs TCA cycle
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uses same rxn types as TCA when looking at conversion of succinate to oxaloacetate
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what would be the result of complete B-oxidation of palmitoyl CoA (C16)
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7 FAD2H (produces 1.5x7 ATP), 7 NADH (produces 7x2.5 ATP), and 8 acetyl CoA (produces 8x10 ATP)
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electron transferring flavoprotein (ETF) fxn
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in mitochondrial matrix, accept electrons from enzyme-bound FAD2H and transfer them to ETF-QO
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electron-transfer flavoprotein-CoQ oxidoreductase (ETF-QO) fxn
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in inner mitochondrial membrane, transfers electrons to CoQ in ETC
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how many ATP are produced for each FAD2H in oxidative phosphorylation in B-oxidation spiral
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~1.5 ATP
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what occurs to unsaturated fatty acids during B-oxidation
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double bonds must be reduced or put into trans form
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what occurs with enzyme deficiency in breaking down medium chain fatty acids
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accumulation of medium-chain fatty acids in blood, and due to solubility in the urine as well
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what occurs with enzyme deficiency in breaking down long chain fatty acids
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fatty acylcarnitines accumulate in the blood; 14 C dominate; do not appear in urine
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when can fatty acid oxidation have products that can be converted to glucose
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odd-chains; propionyl CoA to succinyl CoA, can provide oxaloacetate in liver to produce glucose
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how is B-oxidation regulated by the cells requirement for energy
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fatty acids cannot be oxidized any faster than NADH and FAD2H are reoxidized in the ETC
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when is acetyl CoA carboxylase inhibited in skeletal muscles and liver
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phosphorylated by protein kinase B (AMP-dependent)
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what occurs when malonyl CoA levels decrease
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CPTI activated, B-oxidation restores ATP homeostasis and decrease AMP levels
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what pathways do fatty acids that are not metabolized by B-oxidation enzymes enter
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peroxisomal B and A oxidation and microsomal w-oxidation
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xenobiotic
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all organic cmpds forgein to an organism
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where are very long chain fatty acids synthesized in humans
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brain and nervous system - sphinolipids of myelin
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goal of peroxisomal B and A oxidation
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chain shortening pathways
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how long does peroxisomal B-oxidation spiral continue
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until a medium-chain acyl CoA as short as butyryl CoA is produced
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Zellweger syndrome
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defective peroxisomal biogenesis leading to complex developmental and metabolic phenotypes that mainly affects the brain and liver
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Refsum disease
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deficiency of a single peroxisomal enzyme - phytanoyl CoA hydroxylase- carries out alpha oxidation of phytanic acid
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REfsum disease symptoms
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retinitis pigmentosa, cerebellar ataxia, chronic polyneuropathy
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where is phytanic acid obtained
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solely from diet
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degradation products of chlorophyll that are long-chain branched fatty acids
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phytanic acid and pristanic acid
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why aren't the pathways of a and b peroxisomal oxidation and microsomal w=oxidation feedback regulated
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fxn to decrease levels of water-insoluble fatty acids and xenobiotic cmpds that would become toxic at high concentrations
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when is w-oxidation not a minor process
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conditions that interfere with B-oxidation - produces dicarboxylic acids in increased amounts and they are excreted in the urine
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where are ketone bodies formed in the liver
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in mitochondrial matrix from acetyl CoA generated from fatty acid oxidation
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what happens in the thiolase rxn of fatty acid oxidation
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acetoacetyl CoA to two molecules of acetyl CoA - reversible, but not favorable the other way
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what does acetoacetyl CoA form when reacting with acetyl CoA
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3-hydroxy-3-methylglutaryl CoA (HMG-CoA)
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what is formed from the cleavage of HMG-CoA
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acetyl CoA and acetoacetate
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what determines the ratio of the ketone bodies acetoacetate and B-hydroxybutyrate
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NADH/NAD+ ratio of mitochondrial matrix; under normal conditions the ketone body ratio is 1:1 in the blood
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what cleaves acetoacetate into acetone and CO2
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spontaneous decarboxylation
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what can use keytone bodies aas a fuel source
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most tissues including skeletal muscle, brain, certain kidney cells, intestinal mucosa cells
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why doesn't the liver utilize ketone bodies as fuel
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thiotransferase enzyme not present in sufficient quantities
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prinicple fate of acetyl CoA
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oxidation in TCA cycle
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energy yield from oxidation of acetoacetate
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equivalent of 2 acetyl CoA in TCA cycle (20 ATP) minus activation energy (1 ATP)
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what aa can generate ketone bodies
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leucine, isoleucine, lysine, tryptophan, phenylalanine, tyrosine
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what level of ketones is considered ketoacidosis and why
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>7 mM since this is where ketones exceed bicarb buffer and compensatory respiration occurs
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what do intestinal mucosa cells use for fuel during fasting
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ketone bodies and aas
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what do adipocytes use as fuel during fasting
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ketone bodies
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what can't use ketone bodies as fuel
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liver and RBCs
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what does decreased insulin/glucagon ratio cause in liver
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inhibition of acetyl CoA carboxylase and decreased malonyl CoA levels - activates CPTI allowing fatty acyl CoA to enter B-oxidation
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what happens to fatty acyl CoA in liver once liver has enough fuel
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diverted from TCA cycle into ketogenesis and oxaloacetate is diverted toward malate and into glucose synthesis; regulated by NADH/NAD+ ratio
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what is the NADH/NAD+ ratio during B-oxidation
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relatively high
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where are mutations of LCAD located
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alpha chain
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predicted frequency of MCAD deficiency
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1/15000 people; carrier frequency up to 1/40
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