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MBOD week 11 > Fatty Acid Synthesis > Flashcards

Fatty Acid Synthesis Flashcards

1
Q

T or F: Fatty acid synthesis and oxidation are carried out by different pathways.

A

True

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2
Q

Where does fatty acid synthesis occur?

A
  • Cytosole

Note: breakdown occurs in the mitochondria

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3
Q

What precursors are required for fatty acid synthesis?

A
  • Pantothenic acid
  • NADPH
  • NADH
  • ATP
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4
Q

Where is the enzyme that breaks down citrate located?

- What are its products?

A
  • Citrate Lyase
  • Located in the Cytosol
  • Acetyl CoA and OAA
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5
Q

What is the fate of cytosolic Acetyl CoA?

A
  • It will get made into a fatty acid
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6
Q

How many acetyle CoA molecules are required to make palmitate?
-How many of these acetyl CoA’s have to be 1st converted to malonyl CoA?

A
  • 8 acetyl CoA’s needed

- 7 acetyl CoA’s of the 8 must first be converted to malonyl CoA

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7
Q

What effect does malonyl CoA have on fatty acid degration?

A
  • Prevents Fatty Acids from entering the Mitochondria, which is the only place that degradation can take place
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8
Q

If CPT-1 was mutated and failed to respond to malonyl CoA, what would be the consequence?

A
  • there would be Futile cycle of fatty acid synthesis and breakdown
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9
Q

T or F: after malonyl CoA is made, all reactions of fatty acid synthesis take place on a single enzyme complex

A

True, this is Fatty acid synthase

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10
Q

What type of bonds does Fatty acid synthase make with growing intermediates, and what does it use to make these bonds?

A
  • Acyl Carrier protein part requires phospho-pantetheinyl prosthetic group (CoA)
  • 2 sulfhydral groups are also used
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11
Q

What forms the initial thioester bond with malonylCoA?

A

Panthothenic Acid

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12
Q

Compare the 4 steps of Fatty acid oxidation to Fatty acid synthesis.

A

Oxidation:

  1. Oxidation
  2. Hydration
  3. Oxidation
  4. Cleavage

Synthesis:

  1. Condensation
  2. Reduction
  3. Dehydration
  4. Reduction
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13
Q

What are the 5 steps of Fatty acid synthesis?

A
  1. Transfer - malonyl to FA synthase
  2. Condensation - malonyl and an acyl group
  3. Reducion - ß-ketoacyl group with NADPH
  4. Dehydration - forms double bond
  5. Reduction - of double bond with NADPH
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14
Q

How many carbons are added with each cycle of the FA synthase complex?

A

2 with each round

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15
Q

What MUST be the acceptor of the malonyl transfer?

A

Acetyl CoA

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16
Q

How do VLDLs get broken down and absorbed?

A
  • The same way that Chylomicrons do by LPL
17
Q

T or F: acetyl CoA is the 2 carbon donor used in fatty acid synthesis

A

False, malonyl CoA is the 2 carbon donor

18
Q

What differences are there between enzyme location and structure in fatty acid synthesis and degration?

A
  • In synthesis a Multifunctional Complex is used in the CYTOSOL
  • In degradation separated enzymes are used in the MITOCHONDRIA
19
Q

What is the carrier in fatty acid oxidation and synthesis.

A

Synthesis - ACP

Oxidation - coenzyme A

20
Q

What reducing agents are used in fatty acid oxidation and synthesis?

A

Synthesis - NADPH

Oxidation - NADH and FADH2

21
Q

What are the primary agents for synthesis and oxidation of fatty acids.

A

Synthesis - Liver and Fat

Oxidation - Liver and Muscle

22
Q

How are synthesis and oxidation affected by the insulin/glucagon ratio?

A

High insulin/glucagon = synthesis

Low insulin/glucagon = degradation

23
Q

What step is regulated in fatty acid synthesis and what are the regulators?

A
  • Fatty acyl CoA inhibits Acetyl CoA carboxylase

- Citrate upregulates Acetyl CoA Carboxylase

24
Q

What inhibits ß-oxidation?

A

Malonyl CoA

25
Q

How would you make a Fatty acid that is 22-24 carbons in length starting from acetyl CoA?

A
  1. For up to 16 carbons the chain would be elongated using FAsynthase in the cytoplasm
  2. Greater than 16 carbons, then the chain would be elongated using ELONGASE in the ER
26
Q

T or F: like FAsynthase, Elongase in the ER is a multienzyme complex

A

True

27
Q

What is the 2 carbon donor for elongase?

A

Malonyl CoA

28
Q

What is the fatty acid attached to elongase as it is being elongated?

A
  • Elongation occurs while the Fatty acid is bound to CoA

Note: in FAsynthase elongation occurs while the fatty acid is bound to ACP

29
Q

How many reducing equivalents are needed per 2 carbons added to a fatty acid using elongase, and what is the form of these reducing equivalents?

A

2 NADPH’s needed

30
Q

Where do fatty acids go the become desaturated and by what enzyme?

A
  • Desaturation of fatty acids occurs in the ER

- Enzyme = Fatty Acyl CoA desaturase

31
Q

What is the energetic cost of desaturating a fatty acid?

A

1 NADH

32
Q

What types of unsaturations cannot be achieved by enzymes in the ER?

A

omega 3 or 6

MBOD week 11 (11 decks)

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