B-oxidation (oxidative metabolism of lipids in liver and muscle) Flashcards
what is the major source of energy in liver and muscle ,and in other tissues with the exception of bran and red cells
FATS
The fatty acids oxidation proceeds in both the________and the _________?
peroxisomes and mitochondrion
what are the major end products of b oxidation?
acetyl coa and reduced forms of FADH2 and NADH
in the liver acetyl coa is converted into?
to ketone bodies (ketogenesis)
lipolysis is regulated by hormonal mechanisms involving?
gucagon, epinephrine and cortisol
fatty acids are activated by ?
formation of a high energy thiester bond with coenzyme A
in blood fatty acids are bound to which molecule?
albumin
the length of the fatty acid dictates?
where it is activated to coA
what kind of fatty acids can pass the membrane via passive diffusion?
short and medium chain fatty acids
what is the function of the carnitine shuttle?
bypasses the impermeability of the mitochondrial membrane to coenzyme A
CPT1( carnitine palmitoyl transferase 1 is located in which side of the membrane?
outer side of mitochondrial membrane
an acyl carnitine transporte or TRANSLOCASE in the inner membrane mediates?
the tranfer of acyl-carnitine in to the mitochodrion
what is the function of CPTII
Regenerates the acyl coa
the carnitine shuttle operates in which mechanism?
antiport mechanism
what inhibits the carnitine shuttle ?
MALONYL-COA
The common intermediate in the oxidation of carbohydrates and lipids is ?
ACETYL-COA
The caloric value of fats is about ????
twice that of sugars
on b oxidation, for each cycle was formed?
- acetyl coa
- FADH2
- NADH
- FATTY ACYL-COA with two fewer atoms
oxidation of the B carbon(c-3) facilitates what?
sequential cleavage of acetyl units from the carboxyl end of fatty acids
peroxisomes are involved in the oxidation of?
number of substrates, including urate, and long-,very-long and branched chain fatty acids
peroxisomes is the principal site of production of?
hydrogen peroxide and account for 20% of oxygen consumption in hepatocytes
in peroxisomes b oxidation their acyl-coa dehydrogenase is an?
oxidase rather than a dehydrogenase
what is zellweger syndrome?
defect in import of enzymes into peroxisomes , severe multiorgan disorder leading to death usually at about 6 moths of age
what are fibrates?
class of hypolipidemic drugs that act by inducing peroxisomal proliferation in liver
which type of fatty acids yields to less FADH2 when they are oxidized?
unsaturated - since they are already partially oxidized
odd chain fatty acids produce ?
succinyl coa from propionyl coa
propionyl coa is converted to succinyl coa by?
multistep process involving three enzymes and the vitamins biotin and cobalamin
what kind of oxidation initiates oxidation of branched chain fatty acids to acetyl coa and propionyl coa ?
alfa-oxidation
what are phytanic acids?
branched chain polyisoprenoid lipids found in plan chlorophylls
what is the first and essential step in catabolism of phyanic acids?
alfa oxidation to a pristanic acid , releasing the alfa carbon as carbon dioxide
what is refsums disease?
rare neurological disorder , characterized by accumulation of phytanic acid deposits in nerve tissues as a result of a genetic defect in alfa oxidation.
whats considered an autosomal recessive disease characterized by hypoketotic hypoglycemia , present in infancy and characterized by high concentrations of medium chain carboxylic acids, acyl carnitines and acyl glycines in plasma urine . hyperammonemia may also be present as a reuslt of liver damage
MCDA (medium chain fatty acyl coa dehydrogenase deficiency )
MCAD deficiency is treated with?
frequent feeding, avoidance of fasting and carnitine supplementation
defects in methylmalonyl coa mutase or deficincies in vitamin b12 lead to??
methylmalonic aciduria
what is ketogenesis?
pathway for regenerating coa from excess acetyl coa
in the liver the accumulation of acetyl-coa with concomitant depletion of coa, eventually limits?
b-oxidation
what happens when b-oxidation of fatty acids is impaired?
fatty acids are oxidized, one carbon at a time , by alfa-oxidation or from the omega carbon by microsomal cytochrome P450 -dependent hydroxylases and dehydrogenases.
during gluconeogenesis what is the primary source of ATP?
free coa is required to initiate and continue the cycle of b-oxidation
in gluconeogenesis free coa is regenrated and the acetate group appears in blood in form of ?
3 water soluble lipid derived products: acetoacetate, b-hydroxybutyrate and acetone
ketone bodies involves the synthesis and decomposistion of ?
hydroxymethylglutaryl (HMG)-CoA
The enzymes HMG-COA synthase and lyase are unique to________?
hepatocytes
the appearance of ketone bodies in the urine is an indicator of ?
active fat metabolism and gluconeogenesis
ketogenesis is a result of ?
deficiency in carnitine metabolism
what controls the direct rate of glycogen and glucose metabolism in liver?
insulin, glucagon, epinephrine and cortisol
the process know as lipolysis is controlled by the adipocyte enzyme?
HORMONE SENSITIVE LIPASE
In what kind of disease there are high blood concentrations of cortisol , hyperglycemia, muscle wastage and redistribution of fat from glucagon sensitive adipose depots to atypical sites such as the cheeks, upper back and trunk?
CUSHIING’S SYNDROME
episodes of nonketotic hypoglycemia, development of fulminant heaptic failure, crdiomyopathy, rhabdomyolysis and ocassinally neuropathy and retinopathy are symptoms of ?
long chain l-3 hydroxyacyl coa dehydrogenase (LCAD) deficiency.
in long chain l-3 hydroxyacyl coa dehydrogenase (LCAD) deficiency the most striking feature is ?
association with maternal HELLP(hemolysis,elevated liver enzymes and low platelets) and AFLP( acute fatty liver of pregnancy)
