L-carnitine – Flashcards
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L-carnitine is a ___ ___ amino acid
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zwitterionic quaternary amino acid
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the human body contains about __- __ g
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20-25
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98% of the body's L-carnitine is found where?
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skeletal and heart muscle
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what are the most significant dietary sources of L-carnitine?
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red meat and diary products
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the average non-vegetarian American diet provides about __ to __mg/day
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100- 300
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what contains little or no L-carnitine
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vegetables, cereals, and fruits
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what should vegetarians make sure their diet is adequate in, to maintain normal carnitine biosynthesis?
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lysine, methionine, and micronutrients
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where is L-carnitine absorbed?
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in the intestine using sodium dependent transport
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what is the sodium dependent transport called used by L-carnitine
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organic cation transport number 2 (OCTN2)
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Absorption of L-carnitine appears to be saturated at about a __ gram does
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2
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humans can synthesize L-carnitine from the dietary amino acid __- __
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L-lysine
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syntheisis of L-carnitine begins with the ___ of __- __ by __- ___ (__) to form ___
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methylation, L-lysine, S-adenosylmethionine, SAMe, trimethyllysine
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the biosynthesis is accomplished by a sequence of 5 enzymes which require 5 cofactors: 1. __ 2. __ __ 3. __ 4. __ __- __ 5. ___
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SAMe, vitamin C, iron, vitamin B-6, niacin
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the L-carnitine found in skeletal and cardiac muscle is transported there from the liver and kidenys because of what enzyme?
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gamma-butyrobetaine hydroxylase
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the last enzymatic step in L-carnintine synthesis and is only found in liver and kidney cells
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gamma-butyrobetaine hydroxylase
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carnitine is transported into skeletal muscle ___ a considerable concentration gradient via __ __ __
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against, sodium dependent OCTN2
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Elimination of L-carnitine occurs primarily through the ___
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kidneys
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just like amino acids, 95% of filtered L-carnitine is reabsorbed by the __ __
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renal tubules
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biochemical function of L-carnitine: 1. __ __- __ __ __ __ 2. modulation of __- __ __/ __ __ __
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mitochondrial long-chain fatty acid transport, acetyl-coenzyme A/coenzyme A ratio
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what is L-carnitine's primary function?
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involves the transformation of free long chain fatty acids into long chain acylcarnitine for subsequent transport into the mitochondrial matrix for beta-oxidation
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L-carnitine protects cells against what? and how?
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toxic accumulation of acetyl-CoA compounds by acting as a reservoir for excess acetyl residues which may be generated by high rates of Beta-oxidation
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catalyzes the rate-limiting step in transfer of long-chain fatty acids into the mitochondria
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Carnitine palmitoyltransferse I (CPT I)
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what inhibits CPT I?
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malonyl-CoA during fatty acid synthesis
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can ergogenic or weight loss effct chronic or acute L-carnitine supplementation?
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no
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L-carnitine deficiency can be acquired as a result of what?
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inborn errors of metabolism
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what can a L-carnitine deficiency result in?
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cardiomyopathy, congestive heart failure, encephalopthy, heptomegaly, impaired growth and development in infants and neuormuscular disorders
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what are some pathological manifestations of chronic L-carnitine deficiency ?
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accumulation of lipids within skeletal muscle, cardiac muscle and liver
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appears to decrease L-carnitine synthesis
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Choline supplementation
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can decrease L-carnitine plasma concentrations
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anticonvulsant medications
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what supplementation with the racemic mixture should be avoided and why?
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D, L-carnitine, D-carnitine is not biologically active and acts as a competitive inhibitor for L-carnitine intestinal absorption
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deleterious and potentially toxic impurity as it leads to a functionally relevant depletion of L-carnitine in skeletal and cardiac muscle
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D-carnitine
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Fatty acid accumulation can cause defects in insulin signaling and result in insulin resistance: L-carnitine facilitates the transport of __ __ into the __ for oxidation and this could reduce the lipid overload and improve __ __
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fatty acids, mitochondria, insulin sensitivity
