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Biochemistry > Lipid Metabolism I > Flashcards

Lipid Metabolism I Flashcards

1
Q

Purpose of Malonyl CoA?

A

RLS for FA synthesis!!!

  • Inhibits Carnitine Acyltransferase
  • Prevents the Synthesis and Degradation from occurring SIMULTANEOUSLY
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2
Q

What is a precursor of FA synthesis?

A

Acetyl CoA

- 2C molecule

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3
Q

Steps from Citrate to Pyruvate in the Cytosol

A
  1. Citrate —> ACoA + OAA
    - by Citrate LYASE
  2. OAA ——> Malate
    - by Malate Dehydrogenase
  3. Malate ——> Pyruvate
    - by Malic enzyme
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4
Q

The reactions of the FA synthesis occur on the ___?

A

FA synthase Complex

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5
Q

How does Pyruvate ——> OAA?

A

It is CARBOXYLATED by Pyruvate Carboxylase

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6
Q

What is the “Big Daddy” of the Regulation of ACoA Carboxylase?

A

Phosphorylation (-) and Dephosphorylation (+)

(+)
- Insulin via protein phosphatase

(-)
- Epinephrine
- Glucagon
     (Both by PKA)
- AMP via AMP Kinase
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7
Q

What is the Reducing power of FA elongation?

A

NADPH

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8
Q

Where does FA synthesis primarily occur?

A

The Liver

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9
Q

Phase I steps

A

Cytosolic entry of ACoA

  • Transport of ACoA from Mitochondria to the Cytoplasm
  • ACoA ——> Citrate
  • Citrate transported into the cytosol via the Citrate transporter
  • Citrate ——> ACoA
  • OAA ——> Pyruvate ——>OAA
    (Cytosol) (Cytosol) (Mitoch)
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10
Q

Synthesis of VLDL

A

TAg packaged with Apoproteins to form VLDL

  • Secreted into the blood
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11
Q

What is the C-donor used in the Mitochondria?

A

ACoA

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12
Q

How many reactions must take place in order to create palmitate from Malonyl CoA?

A

7

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13
Q

Major Steps in the synthesis of FA?

A

3 Phases

I: Cytosolic entry of ACoA

II: Generation of Malonyl CoA

III: FA chain formation

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14
Q

How many saturases ado human possess?

A

4 total

Desaturase 4, 5 , 6 & 9

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15
Q

Phase II Steps

A

ACoA ——> Malonyl CoA

  • Catalyzed by ACoA Carboxylase (ACC)
  • Add CO2 to ACoA
  • Uses ATP for energy
  • Uses Biotin as a Co-factor
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16
Q

What LOWERS the FA synthesis?

A

Starvation and High Fat Diets

17
Q

TAG Synthesis Summary

  1. Precursors
  2. Backbone
  3. Net Result
  4. Release
A
  1. Glucose, Glycerol, and FA
  2. G-3-P
  3. Formation of VLDL
  4. Released into the blood
18
Q

Major regulatory enzymes in all the phases of the FAS

A

I: ATP Citrate Lyase

II: ACoA Carboxylase

III: FA Synthase

19
Q

Desaturation of FA’s

  1. Location
  2. Reactants
  3. Enzyme
A
  1. SER
  2. NADPH (or NADH) and O2
  3. ACoA Desaturases
20
Q

Palmitate Synthesis Rxn

A

1 ACoA + 7 MCoA + 14 NADPH + 14 H+

————>

Palmitate + 14 NADP+ + 8CoA + 6 H2O

21
Q

Carbon structure of palmitate?

A

16:0

22
Q

FASynthase

A
  • Multi-enzyme complex
  • 2 identical DIMERS
  • Arranged in Head to Tail confirmation
  • Has 7 enzyme activities
  • Has Acyl carrier protein (ACP)
23
Q

Where is the major source of Carbon for Fatty Acid Synthesis?

A

Dietary Carbs

24
Q

What is the C-donor used in the SER?

A

Malonyl CoA

“S&M”

25
Q

What can enter the inside of the Mitochondrial matrix

A

Both Malate and Pyruvate can both enter the Mitochondria

  • Malate via the Malate-alpha-ketoglutarate transporter
  • Pyruvate via the Pyruvate transporter
26
Q

Phase III Steps?

A

FA Chain Formation

  • 2C of Malonyl CoA are attached to the growing fatty acyl chain to form palmitate
27
Q

TAGs contain ____ times more energy as Carbs (Glycogen)

A

6.75

28
Q

General cycle of FAS

A
  • Needs Cysteine*
    1. Condensation
    2. Reduction
    3. Dehydration
    4. Reduction
  • Repeat 6 more times

“CRDR - CRazy DR.”

29
Q

Allosteric Regulation of ACoA Carboxylase.

  1. Positive
  2. Negative
A
  1. Citrate

2. Long chain FA (Palmitate)

30
Q

What is Leptin?

A

Hormone that suppresses the activity ATP Citrate Lyase

  • Let’s you know that you are full
31
Q

How does Malate ——> OAA?

A

It is OXIDIZED by Malate Dehydrogenase

32
Q

ATP Citrate Lyase Regulation

  1. Stimulation
  2. Inductors of gene expression
  3. Induction counteracted by ?
A
  1. Phosphorylation
  2. Glucose/Insulin
  3. Poly-unsaturated FA (PUFA) & Leptin
33
Q

Gene expression of the regulatory enzymes of FAS are induced by ____?

A
  • Low Fat
  • High CARB diet
  • Insulin
  • Glucocorticoid hormones
34
Q

Where are the secondary sources for FA synthesis?

A

4 sources

  • Brain
  • Adipose tissue
  • Mammary glands (lactating)
  • Kidneys

“BAMK”

35
Q

What is the rate limiting step of Fatty Acid synthesis?

A

Formation for Malonyl CoA from ACoA

36
Q

What is used as a co-factor in the conversion of ACOA to Malonyl CoA

A

Biotin

Biochemistry (12 decks)

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