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Biochem Block 2 > Fatty acid metabolism > Flashcards

Fatty acid metabolism Flashcards

1
Q

Energy yeild

A
  • complete oxidation of FA=9kcal/g

- complete oxidation of proteins or carbs=4kcal/g

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2
Q

Adipose lipase

A
  • constitutive
  • low level release of FA from adipose
  • TAG–>DAG+FA
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3
Q

Hormone-sensitive lipase

A
  • HSL
  • major role in regulated TAG lipolysis
  • release of FA from adipose
  • TAG–>DAG+FA
  • rapid release due to trauma, stroke
  • in response to epinephrine
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4
Q

Lipoprotein lipase

A

-releases fatty acids from TAG in circulating lipoprotein particles to free FA and glycerol

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5
Q

HSL activation

A
  1. phosphorylated and ACTIVATED by cAMP dependent protein kinases
  2. phosphorylation causes HSL binding to perilipin to help it get into droplets and cleave
  3. epinephrine mediated activation
    - Galpha subunit binds to adenylyl cyclase and generates cAMP
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6
Q

cAMP dependent protein kinases

A
  • activate HSL

- inhibit FA synthesis by inhibiting ACC

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7
Q

Insulin

A
  • promotes dephosphorylation of HSL by phosphatases
  • inactivates HSL
  • stops release of FA from TAG
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8
Q

Adipocytes

A
  • lack glycerol kinase

- cant metabolize glycerol released in TAG degradation if all of the FA are released

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9
Q

Glycerol

A
  • released to the blood stream and taken up by the liver
  • phosphorylated in the liver for TAG synthesis OR
  • converted to DHAP for glycolysis or GNG
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10
Q

Fate of FA

A
  • free FA leave adipocytes and bind to serum albumin
  • Taken up by cells and attached to a CoA by thiokinase
  • Fatty acyl CoA is oxidized for energy
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11
Q

Brain and erythrocytes

A
  • do not use FA for energy
  • erythrocytes have no mitochondria
  • Brain: we dont know what they just dont
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12
Q

FA released facts

A
  • 50% of free FA released from adipose TAG are resterified to glycerol 3-P
  • this decreases the plasma free FA level assocaited with type 2 diabetes
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13
Q

Beta-oxidation of FA

A
  • major pathway for obtaining energy from FA
  • occurs in mitochondria
  • FA must be in fatty acyl CoA form
  • successive removal of 2-C fragments
  • fragments are removed from carboxyl end
  • products: acetyl CoA, NADH, FADH2
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14
Q

Thiokinase

A
  • located on the cytosolic side of mitochondrial outer membrane and generates LCFA CoA in the cytosol
  • LCFA CoA cannot directly cross mitochondrial membrane because of CoA
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15
Q

CAT-I inhibition

A
  • inhibited by malonyl CoA
  • prevents LCFA transfer from CoA to Carnitine
  • inhibition prevents mitochondrial import and beta oxidation of LCFA
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16
Q

Carnitine

A
  • obtained from diet of synthesized
  • meat products
  • synthesized: pathway in liver and kidney using lysine and methionine
  • babies dont have a lot because they dont eat meat
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17
Q

Skeletal muscle and canitine

A

-skeletal muscle houses 97% of carnitine in body

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18
Q

Secondary Carnitine deficiency

A

caused by…

  • decreased synthesis by liver disease
  • dietary restrictions
  • hemodialysis(removes carnitine)
  • conditions when carnitine requirements increase(pregant, big changes)
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19
Q

Primary Carnitine deficiency

A

caused by congenital deficiencies in…

  • renal tube re absorption of carnitine
  • carnitine uptake by cells
  • CAT I and II function
  • impaired flow of a metabolite from one cell compartment to another results in pathology
  • Treatment: avoid fasting, eat high carbs, eat low LCFA diet, supplement medium chain FA
20
Q

CAT-I genetic defect

A
  • decreased LIVER use of LCFA during fast

- severe hypoglycemia, coma, death

21
Q

CAT-II genetic defect

A
  • HEART AND SKELETAL MUSCLE exhibit symptoms that range from cardiomyopathy, muscle weakness, myoglobinemia, after exercisin
  • problem with energy production in muscles
22
Q

entry of short and medium chan=in FA to mitochondria

A
  • they do not need carnitine of CAT systems
  • once inside matrix, they are activated to CoA by thiokinase
  • not regulated by malonyl CoA
  • human milk is high in short and medium chain
23
Q

Acetyl CoA and pyruvate carboxylase

A
  • Acetyl CoA is a POSITIVE allosteric effector of pyruvate carboxylase
  • linking FA oxidation to GNG
24
Q

Energy yield from Beta-Oxidation

A
  • energy yield is high

- degrading 1 palmitoyl CoA to CO2 and H20= net 129 ATP produced

25
Q

Greatest flux through B-oxidation pathway

A

Synthesis of FA: after carb-rich meal

Degredation of FA: starvation

26
Q

Vitamin B12 Deficiency

A
  • causes excretion of both propionate and methylmalonate in urine
  • heritable methylmalonic acidemia
  • mutase is missing
  • cant convert vitamin B12 to coenzyme form
27
Q

Oxidation of unsaturated fatty acids

A

unsaturated FA: release less energy than saturated, less highly reduced, fewer reducing equivalents can be produced
-require additional enzymes for complete oxidation

28
Q

Monounsaturated fatty acids

A

-required an additional isomerase enzyme

29
Q

Polyunsaturated Fatty acids

A

-require an isomerase and reductase enzyme

30
Q

Beta-Oxidation in the peroxisome

A
  • VLCFA 22 carbons or longer are initially oxidized in th peroxisome
  • the partially oxidized shorter chain can be imported to the matrix by diffusion for further oxidation
  • DOES NOT GENERATE ATP
31
Q

Zellweger syndrome

A
  • peroxisome biogenesis disorder
  • genetic defects that result in failure to target matrix proteins to the peroxisome
  • getting it into peroxisome
  • accumulation of VLCFA in blood and tissues
32
Q

X-Linked adrenoleukodystrophy

A
  • genetic defects causing the failure to transport VLCFA across peroxisome membrane
  • digesting it
  • disconnect in understanding surroundings/environment
  • cause accumulation of VLCFA in blood and tissues
33
Q

Alpha oxidation of FA

A
  • Branched chains, 20 C FA phytanic acid cannot function as a substrate for acetyl CoA dehydrogenase due to methyl group at Beta position
  • Payanoyl CoA alpha-hydroxylase: hydroxylates the alpha carbon and carbon 1 is released as CO2
  • 19C pristanic acid is activated to CoA and undergoes Beta oxidation
34
Q

Refsum disease

A

-peroxisomal phyH deficiency
-phytanic acid accumulates in blood and tissues
-symptoms are neruologic
Treatment: have less branched chained FA in diet

35
Q

MCAD deficiency

A
  • Medium chain FA acetyl CoA dehydrogenase
  • lose like half of beta oxidation energy
  • one of most common inborn errors in metabolism
  • MOST common inborn error of FA oxidation
  • possible cause for SIDS
36
Q

Ketone bodies

A
  • acetoacetate
  • 3-hydroxybuterate: transported in blood to peripheral cells/tissues
  • Acetone: a dead-end by product
  • peripheral cells convert ketone bodies into acetyl CoA as substrate for TCA cycle
37
Q

Ketone body fuel source

A
  • energy for peripheral cells
  • soluble in aqueous solution-no lipoprotein or albumin transport required
  • produced in liver when acetyl CoA levels supersede oxidation capacity
  • use is proportional to concentration in the body
  • decrease body demand for glucose
38
Q

Hypoketosis

A

-due to decreased acetyl CoA availability

39
Q

Hypoglycemia

A

-due to increased reliance on glucose for energy

40
Q

HMG CoA synthase

A
  • rate limiting step in ketone body synthesis

- only present in liver to significant amounts

41
Q

Ketolysys

A
  • 3 hydroxybuterate is oxidized to produce NADH in peripheral tissues
  • acetoacetate then meets CoA
  • Acetoacetyl CoA is converted to 2 acetyl CoA
  • extrahepatic cells having mitochondria can conduct this process, liver cannot use ketone bodies as fuel because it lacks thiophorase
42
Q

Ketonemia

A

-ketone body levels rise in blood

43
Q

Ketonuria

A

-ketons body levels rise in urine

44
Q

Diabetes mellitus

A
  • type 1

- urinary excretion levels rise and blood concentrations rise

45
Q

Diabetic ketoacidosis

A

-fruit smelling breath from acetone
-ketonemia causes acidemia because carboxyl group on ketone bodies has pka of 4, each H released lowers blood pH
-increased ketone bodies and glucose causes increaed secretion of water
Ketoacidosis: decreased blood volume increased H+ concentration causing acidosis(can be caused by fasting)

Biochem Block 2 (11 decks)

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