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Foundations 1 > 1-7 Lipid Metabolism > Flashcards

1-7 Lipid Metabolism Flashcards

1
Q

Fatty Acid Oxidation overview

A

Mjor source of E btw meals and during increased demand

during fasting provides ketone bodies as fuel

higher E yield per mole than glucose

mito matrix

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2
Q

Transport of FA in mito

A

Cytosol
1. Long chain FA + ATP + coA via ACYL COA SYNTHESTASE -> Fatty acyl CoA + AMP +PPi

Intermembrane space

  1. Fatty acyl CoA move to interembrane space
  2. Fatty actyl CoA + Carnitine via CPT1 ->CoA + Fatty acylcarnitine

Matrix

  1. Fatty acylcarnitine via CARNITINE ACYLCARNITINE TRANSLOCASE move to matrix
  2. Fatty acylcarnitine + CoA via CPT2 -> Fatty acyl coA (ready for b oxida) + Carnitine (shuttled back into intermembrane space)

Short and medium chain FAs can be shuttle direction through MCT into matrix

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3
Q

B oxidation

A
  1. oxidation: ACYL COA DEHYDROGENASE- oxidizes FA to a double bond and reduces FAD to FAD(2H) (1.5 ATP)
  2. hydration: ENOYL COA HYDRALASE- adds H2O
  3. oxidation: B-HYDROXY ACYL DEHYDROGENASE- oxidizes FA alcohol to ketone reduces NAD+ to NADH + H+ (2.5ATP)
  4. cleavage: B-KETO THIOLASE- cleaves 2 carbons and adds coA to make acetyl coA + shortened FA-coA
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4
Q

Oxidation of Odd chain FA

A

Odd chain FA b-oxi to propionyl-CoA

  1. propionyl-CoA + ATP +CO2-biotin via PRIOPIRONYL-COA CARBOXYLASE -> AMP + PPi + methyl malonyl-coA // intermediate // succinyl coA (citric acid cycle)

Essentially: can move 3C FA to citric acid cycle via rearrangement and energy

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5
Q

ATP yield from b-oxi of palmitate

A

7 oxidation spirals:

7 FAD(2H) = 10.5 ATP from oxi phos
7 NAD(2H) = 17.5 ATP from oxi phos
8 AcetylCoA = 80 ATP from oxidation in TCA

Required 2 ATP from activation step to get across cytosol membrane

Sum: 106 ATP

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6
Q

Regulation of B oxidation

A

+: High levels of FA induce transcription of enzyme genes

Fatty acyl CoA –> Fatty acyl carnitine, inhibited by malonyl coA (it is intermediate of FA synth!)

ATP/ADP ratio high inhibits ETC thereby increases NADH and FAD(2H) which inhibits B-oxidation (because they are products)

Essentially: reduce Boxi when ATP high

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7
Q

Peroxisomes

A

**oxidation of very long chain FAs, contain catalase
detox of phenols fraldehyde alchohols
Synth plasmalogens

**Long chain FA-coA + FAD via OXIDASE -> FAD(2H) + shorterFA-coA (can now be transformed to acetyl carnitine or SCFA-carnitine and shuttles to mito matrix)

FAD(2H) + O2 -> H2O2 (Toxic) via CATALASE -> H2O + .5 O2

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8
Q

alpha oxidation of phytanic acid in peroxisomes

A

branched FA, alphaoxidation cleaves branches so betaoxidation can occur

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9
Q

omega oxidation

A

in ER, omega carbon is farthest away from carbonyl

  1. methane oxidized to alcohol further oxidized to carboxylic acid, compound now a dicarboxylic acid (very soluble)
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10
Q

Oxidation of ketone bodies

A

in peripheral tissues

  1. Beta-hydroxybutyrate (alcohol) + NAD+ via B-HYDROXYBUTYRATE DEHYDROGENASE -> NADH + H+ + acetoacetate (ketone)
  2. acetoacetate + Succinyl coA(from TCA) via TRANSFERASE -> acetoacetyl coA + succinate
  3. acetyoacetyl coA + coASH via THIOLASE -> 2 acetylCoA
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11
Q

Alcohol metabolism

A
  1. Ethanol + NAD+ via ALCOHOL DEHYDRGENASE CYTOSOL -> NADH + H+ + Acetaldehyde
  2. Acetaldehyde + NAD+ via ACETALDEHYDE DEHYDROGENASE MITOCHONDRIA -> Acetate + ANDH + H+
  3. Acetate + coASH + ATP via ACETYL COA SYNTHETASE -> acetylcoA

Also happens on membrane of ER with MEOS (microsomal ethanol oxidizing system) to turn ethanol to acetaldehyde

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12
Q

FA synth: production of cytosolic acetylcoA

A

Cytosol
1. Glucose via glycolysis -> pyruvate

Mitochondria

  1. pyruvate via PYRUVATE CARBOXYLASE -> OAA
  2. 1 pyruvate PYRUVATE DEHYDROGENASE -> Acetyl coA
  3. OAA + Acetylcoa -> citrate, exits mitochondria

Cytosol

  1. citrate via CITRATE LYASE -> OAA + AcetylcoA (for FA synth)
  2. 1 OAA + NADH via CYTOSOLIC MALATE DEHYDROGENASE -> Malate + NAD+
  3. Malate + NADP+ via MALIC ENZYME -> Pyruvate (ready to cycle into mitochondria) + CO2 + NADPH
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13
Q

FA synth: sources of NADPH

A
  1. Pentose Phosphate pathway: G6P + NADP+ -> F6P + NADPH

2. Malate + NADP+ -> Pyruvate + NADPH

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14
Q

FA synth: Synthesis of malonylCoA

A

Citrate in cytosol -> OAA + Acetyl coA

  1. Acetyl coA + CO2(biotin) + ATP via ACETYL COA CARBOXYLASE -> ADP + Pi + Malonyl coA

reversed with MALONYL COA DECARBOXYLASE

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15
Q

Regulation of acetyl coA carboxylase

A

Cytosol:
Acetyl coA + CO2(biotin) + ATP via ACETYL COA CARBOXYLASE -> ADP + Pi + Malonyl coA

Direct:
+: Citrate
-: Palmitoyl coA

Phosphorylation inactivates
AMP-activated protein kinase adds P group (increased activity under low energy levels)
Phosphatase removes P group (increased activity under high insulin levels)

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16
Q

Regulation of CPT1

A

Cytosol:
Malonyl CoA inhibits CPT1 to stop transport of FAcoA+Carnitine into intermembrane space, because malonyl coA substrate for FA synthase and wants to inhibit b oxidation of FAs

17
Q

Synthesis of palmitate

A

on FATTY ACID SYNTHASE on cytosolic side of ER

AcetylcoA gives the first C, all others from malonylcoA

  1. Condensation: removes CO2 and coASH
  2. Reduction: NADPH to NADP+
  3. Dehydration: removes H2O
  4. Reduction: NADPH to NADP+

Adds 2 Cs at a time

18
Q

Desaturation of FAs

A

saturated FA + O2 +2H+ via FATTY ACYL COA DESATURASE -> H2O + Monosaturate FAcylCoA

This can happen at C9, C5, C6

19
Q

Synth Ketone bodies (when, where, mech)

A

When: fasting, carb restriction
Where: mitochondria of hepatocytes

  1. 2 acetylCoA via THIOLASE -> coASH + acetoacetylCoA
  2. acetoacetylCoA + acetylcoA via HMG COA SYNTHASE -> HMGcoA
  3. HMGcoA via HMG COA LYASE -> acetylcoa + acetoacetate
  4. acetoacetate +NADH+H via B HYDROXYBUTYRATE DEHYDROGENASE-> B-hydoxybutyrate + NAD+
  5. 1 acetoacetate spontaneous loss of CO2 -> acetone
20
Q

Regulation of ketone body synthesis

A
  1. ) High levels of FA lead to
  2. ) high levels of CPT1 and thereby low levels of malonyl coA
  3. ) This produces high levels of FA-carnitine transformed to FA-CoA in mido matrix, and high levels of ATP from ETC inhibit Boxidation process but
  4. )b oxidation occurs producing high levels of acetyl coA which are transformed to acetoacetyl coA and then produce ketone bodies
    - acetyl coA could also be transformed to citrate but ISOCITRATE DEHYDROGENASE in inhibited by high NADH so cannot catalyze rxn to malate
  5. ) OAA is being converted to malate because high NADH levels (OAA + NADH -> NAD+ + malate), malate sent for gluconeogenesis
21
Q

Ketogenic AAs

A

Source of keton bodies during starvation, produce acetyl coA and or acetoacetate

22
Q

Synth of triacylglycerol

A

Liver: glycerol + ATP via GLYCEROL KINASE -> ADP + Glycerol3p
Liver/adipose: Glucose -> Dihydorzyacetonephosphate->Glycerol3P

Glycerol3P -> Phosphatidic acid -> DAG -> triacylglycerol (blood vldl OR adipose stores)

23
Q

Degradation of triacylglycerol (type of enzyme)

A

Done with lipases

24
Q

Synth membrane phospholipids (2 routes, starting material)

A

Phosphatidic acid

Route 1:

  1. Phosphatidic acid -> DAG + Pi
  2. DAG + CDP-headgroup -> Glycerophospholipid + CMP
  3. Glycerophospholipid forms “phosphatidyl”choline, ““ethanolamine, ““serine

Route 2:

  1. Phosphatidic acid +CTP -> CDP-DAG + PPi
  2. CDP-DAG + headgroup -> Glycerophospholipid + CMP
  3. Glycerophospholipid forms “phosphatidyl”inositol, cardiolipin, ““glycerol
25
Q

Isoprenoid / Cholesterol synthesis

A
  1. Acetyl-coA + acetoacetyl-coA -> HMG-CoA
  2. HMG-CoA +2NADPH via HG COA REDUCTASE (inhibited by statins) -> mevalonate + NADP+
  3. mevalonate -> isopentenylPP // dimethylallylPP -> geranyl ->farnesyl->squalene —-> cholesterol

Foundations 1 (41 decks)

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