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Block 3 > MMT: fatty acid biosynthesis > Flashcards

MMT: fatty acid biosynthesis Flashcards

1
Q

What is the main product of fatty acid synthase?

A

Palmitic acid

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2
Q

What are the transporters of fatty acids in the fed state?

A

Chylomicrons and VLDL

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3
Q

What are the transporters of fatty acids in the fasting state?

A

Albumin

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4
Q

In the fed state, fatty acids are released by?

A

LPL in the capillaries

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5
Q

In the fasting state, fatty acids are released by?

A

Hormone-sensitive lipase in adipocytes

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6
Q

What are the 4 major stages of palmitate formation?

A
  1. Pyruvate formation 2. Citrate formation 3. Malonyl CoA formation 4. Palmitate
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7
Q

What is the rate limiting enzyme of fatty acid synthesis?

A

Acetyl CoA carboxylase

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8
Q

In the fed state, what drives the formation of citrate?

A

Acetyl CoA buildup

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9
Q

How does the high insulin/glucagon ratio in the fed state drive formation of citrate?

A

It reduces the need for gluconeogenesis and upregulates glycolysis, allowing oxaloacetate that is formed to be used to make citrate

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10
Q

How does a high ATP/ADP ratio in the fed state impact the formation of citrate?

A

It reduces the need for acetyl CoA to be used in the citric acid cycle, making it available to make citrate

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11
Q

What enzyme is upregulated in the fasting state to promote formation of oxaloacetate?

A

Pyruvate carboxylase

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12
Q

What vitamin is needed to produce malonyl CoA from acetyl CoA?

A

Biotin (acetyl CoA carboxylase)

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13
Q

Malonyl CoA inhibits…? What is the significance of this?

A

CPTI; upregulates fatty acid synthesis instead of oxidation

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14
Q

What is the ‘short arm’ of fatty acid synthase?

A

Cysteine; associated with acetyl group

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15
Q

What is the ‘long arm’ of fatty acid synthase?

A

ACP; associated with malonyl group

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16
Q

What is the structure of fatty acid synthase?

A

A dimer that makes 2 palmitic acids at a time

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17
Q

What is the 4-reaction cycle of fatty acid synthesis?

A
  1. Condensation 2. Reduction 3. Dehydration 4. Reduction
18
Q

What is used as a reducing agent in fatty acid synthesis?

A

NADPH

19
Q

Where does fatty acid synthesis occur?

A

The cytoplasm

20
Q

What happens once palmitate is formed?

A

It is released from fatty acid synthase and converted to palmitoyl CoA

21
Q

What enzyme forms palmitoyl CoA?

A

Fatty acyl CoA synthase

22
Q

What is the major control point of fatty acid synthesis?

A

Acetyl CoA carboxylase

23
Q

What are the main regulatory methods of acetyl CoA carboxylase?

A

Phosphorylation and allosteric modulators

24
Q

More citrate will __ fatty acid synthesis?

A

Promote

25
Q

More palmitoyl CoA will __ fatty acid synthesis?

A

Reduce

26
Q

Describe the regulation of ACC in the fed state.

A

Insulin promotes a phosphatase that promotes formation of malonyl CoA and thus inhibition of CPTI. This leads to synthesis of fatty acids.

27
Q

Describe the regulation of ACC in the fasting state.

A

High AMP causes AMPK to phosphorylate ACC, causing less malonyl CoA. This will promote fatty acid oxidation as opposed to synthesis.

28
Q

What enzymes upregulate fatty acid synthesis due to insulin?

A

Malic enzyme and citrate lyase

29
Q

Elongation of fatty acids occurs in the…

A

ER

30
Q

Where does VLC FA oxidation take place?

A

Peroxisomes

31
Q

What are the steps for elongation of fatty acids?

A

Same as synthesis! 1. Condensation 2. Reduction 3. Dehydration 4. Reduction

32
Q

In unsaturated fatty acids, where can we introduce double bonds?

A

Carbon 4, 5, 6, and 9, but not beyond 9!!

33
Q

What is fatty acyl CoA desaturase?

A

A membrane-bound oxygenase that desaturates fatty acids in the ER

34
Q

What does desaturation require to occur?

A

Iron

35
Q

What are the main functional roles of fatty acids?

A
  1. Serve as fuel 2. Make up TGs and phosphoacylglycerols 3. Serve as hormones and intracellular messengers
36
Q

Why does the brain not use free fatty acids for fuel?

A
  1. ATP generation from beta oxidation demands more oxygen than from glucose, which increases risk of neural hypoxia 2. Superoxide is generated in beta oxidation which can cause oxidative stress 3. Rate of ATP generation is slower than that of glucose
37
Q

What is the starting molecule for phosphoacylglycerol?

A

G3P

38
Q

Other than cell membranes, where can phosphoacylglycerols be found?

A

Outside of lipoproteins

39
Q

What are eicosanoids?

A

Molecules formed from arachidonic acid that act as local hormones; they can cause inflammation, clotting, smooth muscle contraction, etc

40
Q

Where is arachidonic acid in the cell membrane?

A

In the fatty acid tails of phospholipids

41
Q

What are the pathways of eicosanoid synthesis?

A

COX and LOX

42
Q

Aspirin and ibuprofen block…

A

COX

Block 3 (52 decks)

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