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(J) Biochemistry Test 3 > Lecture 28 - Lipid Metabolism I > Flashcards

Lecture 28 - Lipid Metabolism I Flashcards

1
Q

What is the major source for fatty acid synthesis?

L28 S4

A

Dietary carbohydrates

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3
Q

In what tissues do fatty acid synthesis occur?

L28 S5

A
  • liver (primary)
  • adipose tissue
  • brain
  • kidney
  • lactating mammary glands
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4
Q

What is the precursor of fatty acid synthesis?

L28 S6

A

Acetyl-CoA

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5
Q

What are the major steps of fatty acid synthesis?

L28 S8

A
  • movement of mitochondrial acetyl CoA to the cytoplasm
  • generation of malonyl CoA (carboxylation)
  • fatty acid chain formation
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6
Q

What steps are involved in transport of mitochondrial acetyl CoA to the cytoplasm?

L28 S11-12

A
  • condensation with oxaloacetate to for citrate (via citrate synthase)
  • transport of citrate from mitochondria
  • conversion back to acetyl CoA (via ATP citrate lyase)
  • oxaloacetate reduce to malate (via malate dehydrogenase)
  • oxaloacetate transported back into the mitochondria via malate-α ketoglutarate transporter and oxidized back to oxaloacetate (via malate dehydrogenase)
  • *or**
  • malate converted to pyruvate in cytoplasm (via malic enzyme) then transported into mitochondria
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7
Q

What are the regulators of citrate lyase?

L28 S13; 29

A

Activators:

  • glucose
  • insulin

Inhibitors:

  • PUFA
  • leptin
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8
Q

What is the function of acetyl CoA carboxylase?
What special features does it have?

L28 S14

A

Carboxylates acetyl CoA using CO2 to form malonyl CoA.

Uses ATP for bond energy.

Uses biotin as cofactor.

**rate limiting step

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9
Q

What are the regulators of acetyl CoA carboxylase?

L28 S13;30

A

Activators:

  • citrate
  • insulin

Inhibitors:

  • glucagon
  • epinephrine
  • AMP
  • palmitate
  • PUFA
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10
Q

What is the function of fatty acid synthase complex?
What special features does it have?

L28 S17-18

A

In seven reactions it takes 7 malonyl CoA, 1 acetyl CoA, and 14 NADPH to form palmitate (16C).

Complex formed of two identical dimers that have 7 catalytic activities and a acyl carrier protein (ACP).

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11
Q

What are the regulator of the fatty acid synthase complex?

L28 S17;31

A

Activators:

  • insulin
  • glucocorticoid hormones

Inhibitors:
-PUFA

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12
Q

What is the total equation for the reactions catalyze by fatty acid synthase?

L28 S21

A

Reactants:

  • 1 acetyl CoA
  • 7 malonyl CoA
  • 14 NADPH
  • 14 H+

Products:

  • palmitate
  • 14 NADP+
  • 8 CoA
  • 6 H2O
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13
Q

What are the reactions catalyzed by fatty acid synthase?

L28 S22

A
  • condensation
  • reduction
  • dehydration
  • reduction
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14
Q

What occurs in the first condensation step catalyzed by fatty acid synthase?

L28 S24

A

Acetyl ACP + malonyl ACP -> acetoacetyl ACP + CO2 + ACP (from acetyl)

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15
Q

What occurs in the first reduction step catalyzed by fatty acid synthase?

L28 S24

A

Acetoacetyl ACP + NADPH -> D-3-hydroxybutyryl ACP + NADP

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16
Q

What occurs in the first dehydration step catalyzed by fatty acid synthase?

L28 S25

A

hydroxybutyryl ACP -> crotonyl ACP + H2O

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17
Q

What occurs in the second reduction step catalyzed by fatty acid synthase?

L28 S25

A

Crotonyl ACP + NADPH -> butyryl ACP + NADP+

18
Q

What are the main sources of NAPDH?

L28 S23

A
  • pentose phosphate pathway

- malic enzyme

19
Q

How and where are fatty acids longer than palmitate (C16) generated?

L28 S33

A

Location:

  • smooth ER (uses malonyl CoA)
  • mitochondria (uses acetyl CoA)

Synthesized by addition of 2 carbon groups.

NADPH used as reducing agent.

20
Q

How and where are unsaturated fatty acids generated or obtained from?

L28 S34

A

Catalyzed by acyl CoA desaturases in the SER

4 variaties of desaturaes:

  • Δ4 (between carbon 4-5)
  • Δ5 (between carbon 5-6)
  • Δ6 (between carbon 6-7)
  • Δ9 (between carbon 9-10)

Use NADH/NADPH as reducing agent

Fatty acids with double bonds beyond carbon 9-10 (omega 3 and 6 FAs) cannot be synthesized by humans and must be ingested

21
Q

What are eicosanoid hormones?

L28 S42

A

Hormones derived from arachidonate (20:4)

e.g. prostaglandins, prostacyclin, thromboxanes, and leukotrines

These hormones are all local and short lived.

Binds GPCRs

(J) Biochemistry Test 3 (10 decks)

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