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CHEM- 3503 > Chapter 19: Lipid Metabolism > Flashcards

Chapter 19: Lipid Metabolism Flashcards

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1
Q

How is the glycerol portion of the TAGfat catabolized ? Where does this occur? Draw a mechanism

A

the glycerol is metabolized by phosphorylation followed by an oxidation of glycerol 3 phosphate. this occurs in the cytosol.

This process utilizes an ATP and makes an NADH

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2
Q

3 main steps of catabolism of the fatty acid component of fats

A

1) add a co! to the cytosol
2) transport into the mitochondria (because coA cannot go on its own)
3) oxidize into acetyl coA by beta oxidation

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3
Q

Draw out the mechanism of adding a coA to a fatty acid. How many ATP does this take?

A

take 2 atp. refer to notes.

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4
Q

How is the Fatty acyl CoA transported into the mitochontdria? Draw the shuttle

A

via the carnitine carrier protein. coA of the fatty acyl is replaced with carnitine, which crosses, then carnitine is replaced with matrix coA.

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5
Q

Beta oxidation produces ___ NADH and ___ FADH2 per cycle, in addition to acetyl coA

A

1 NADH and 1 FADH2

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6
Q

beta oxidation forms a double bond between ____ and ___ carbons

A

between alpha and beta carbons.

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7
Q

outline the process of fatty-acyl coA oxidation. Draw the mechanism is which a Fatty-acylCoA gets oxidized to form a fatty acylCoA 2 carbons shorter

A

FAD to FADH2 creates a double bond (now trans enoyl)

  • add water across a double bond (hydroxyacyl coA)
  • oxidize hydroxyl to ketone (keyoacyl coA)
  • cleave acetyl coA, leave the ketone at the end of the FA chain, chain is now 2 carbons shorter.
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8
Q

How many ATPS is an 18:0 FA unsaturated chain worth?

A

roughly 120-122

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9
Q

What happens do the position of the trans double bond during the oxidation of a monounsaturated FA? (at 9th position)

A

the position is at 3rd carbon instead of 2nd carbon. The bond gets moved over instead of FAD creating a new bond, therefore, you get one less FADH then you would during unsaturated oxidation.

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10
Q

In an odd chain fatty acid oxidation, the last step of beta oxidation forms ____, which can eventually form succinyl-coA and then succinate.

A

propionyl-coA

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11
Q

T/F humans can make glucose out of odd chain fatty acids.

A

true. 1 glucose can be made or every 2 odd chain FA’s metabolized.

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12
Q

how does ACC play a role in the regulating FA oxidation?

A

ACC converts acetyl coA into malonyl coA, which prevents the transportation of Fatty acyl coAs into the mitochondria (blocks carnitine shuttle).

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13
Q

T/F Fatty acid oxidation is regulated by insulin and glucagon

A

true. if you are well fed, there is insulin present, which means you do not need break down fatty acids. insulin activates ACC, which turns acetyl coA into malonyl coA, which prevents transportation of fatty acyl coAs into the mitochondria.

glucogon does the reverse, and deactivates ACC, allowing fatty acids to go into the mitochondria for oxidation. this occurs under hungry conditions.

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14
Q

T/F Fatty acid oxidation is regulated by insulin and glucagon

A

true. if you are well fed, there is insulin present, which means you do not need break down fatty acids. insulin activates ACC, which turns acetyl coA into malonyl coA, which prevents transportation of fatty acyl coAs into the mitochondria.

glucogon does the reverse, and deactivates ACC, allowing fatty acids to go into the mitochondria for oxidation. this occurs under hungry conditions.

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15
Q

Draw beta hydroxybutyrate and acetoacetate, both ketone bodies.

A

see notes

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16
Q

Purpose of ketone bodies

A

allows the body to reduce the rate at which muscle mass is lost supporting gluconeogenesis, and rely more on fat stores during times of starvation.

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17
Q

What organ degrades fatty acids into ketone bodies?

A

the liver.

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18
Q

Draw the mechanism acetoacetate is formed from fatty acids.

A

fatty acids turn into acetyl coA, which form acetoacylcoa, which can form acetoacetate and acetyl coA

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19
Q

How can acetoacetate create betahydroxybutyrate

A

via the oxidation of an NADH, creating NAD+

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20
Q

How can acetoacetate create betahydroxybutyrate

A

via the reduction of an NAD+

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21
Q

Why does Krebs cycle slow down during starvation?

A

the liver is undergoing gluconeogenesis to maintain glucose supply, using oxaloacetate. oxa levels drop, slowing down krebs, and making acetyl coA accumulate since krebs is not burning as much. acetyl coA is then funneled for ketone body formation.

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22
Q

Where does CATABOLISM of ketone bodies take place? what are ketone bodies broken down into?

A

catabolism of ketone bodies take place in bodily tissues. they break them down into 2 acetyl coA. (Recall, acetyl coA cannot cross membranes that well, and so the liver makes them into ketone bodies before delivering them to extra-hepatic tissues)

23
Q

draw the mechanism of betahydroxybutarate catabolizing into acetyl coA

A

makes 2 acetyl coAs

24
Q

In humans, FA oxidation, ketone body synthesis, and Fatty acid elongation occur in ___

A

the mitochondria

25
Q

in humans, NADPH production via the PPP, sterol synthesis, and FA synthesis occurs in the ____

A

cytosol,

26
Q

in plants, where are NADPH, ATP, and Fatty acid synthesis reactions located?

A

in the chloroplasts

27
Q

Where does fatty acid oxidation take place in plants?

A

Peroxisomes

28
Q

essentially, for mammals: FAs are catabolized in the ____ and synthesized in the _____

A

FAs are catabolized in the mitochondria and synthesized in the cytosol

29
Q

essentially, for mammals: FAs are catabolized in the ____ and synthesized in the _____

A

FAs are catabolized in the mitochondria and synthesized in the cytosol

30
Q

In beta oxidation, NAD+ and FAD+ are electron acceptors. In Fatty acid synthesis, what molecule contributes electrons?

A

NADPH.

31
Q

2 main things you need to make fatty acids?

A

acetyl coA and NADPH.

32
Q

What’re the 2 major ways of getting NADPH? Draw the mechanism

A

1) malic enzyme; making NADPH from malate into pyruvate.

2) Pentose Phosphate Pathway in the cytosol. Turns glucose 6 phosphate into ribulose 5 phosphate.

33
Q

The tricarboxylate transport system transport ____ out of the mitochondria, while transporting _____ into the mitochondria. This allows ____ to be produced for fatty acid synthesis in the cytosol. NADPH is also produced, which is a plus, because that is also needed for fatty acid synthesis.

A

The tricarboxylate transport system transports CITRATE out of the mitochondria, while transporting PYRUVATE into the mitochondria. This allows ACETYL COA to be produced, to be used for fatty acid synthesis in the cytosol.

34
Q

How does Acetyl-coA get transported into the cytosol for fatty acid synthesis?

A

the tricarboxylate transport system.

35
Q

draw the tricarboxylate transport system

A

refer to notes.

36
Q

Instead of converting malate into pyruvate in the tricarboxylate transport system before exporting it into the matrix, the malate could go via the malate-alpha ketoglutarate transporter back into the matrix. What is a benefit of this alternative route?

A

the alternative system can make NADH in the matrix. It trades a cytosolic nadh for a mitchondrial NADH. this costs 1 less atp than the tricarboxylate transport system, which brings nADPH into the cytosol. (because pyruvate does not need to be made into oxaloacetate in the mitochondria.)

This alternative method however, does not make NADPH because it skips making pyruvate from malate.

37
Q

What must acetyl coA be made into before it can undergo fatty acid synthesis? draw te mechanism. Where does this happen?

A

malonyl coa via the ACC. costs 1 ATP. happens in the cytosol.

acetyl coA + ATP+ CO2–> malonyl coA + ADP + Pi

38
Q

when making fatty acids, acetyl co A and malonyl co A get attached to the _____ carrier, which is part of the FA synthase complex

A

the Acyl carrier protein.

39
Q

What kind of fatty acid chain is produced by fatty acid synthase?

A

always a 16:0 chain. if you need a different kind of chain, the 16:0 chain gets modified in the ER .

40
Q

Outline the events that happen on ACP of FA synthase to create a Fatty acid. Draw the mechanism

A

1) acetyl coA and malonyl coA are covalently attached to synthase on the ACP.
2) acetyl groups attack the 2nd carbon of the malonyl group
2) the beta keto gets reduced to beta hydroxy.
3) beta-hydroxy gets dehydrated and becomes a double bond.
4) double bond gets reduced and becomes butyryl-ACP
5) butryl acP moves to site where acetyl coA was originally. A new malonyl coA is attached to the vacant site. the cycle continues until FA 16:0 has been made.

41
Q

How much NADPH is expended during FA synthesis of a 16:0 saturated FA? How many electrons in total is added ?

A

2 NADPH. One for converting a ketone into a hydroxyl, and the other for converting the double bond to single bond. 4 electrons are thus needed to add 2 carbons to a fatty acid chain.

42
Q

T/F A fatty acid is built from head to tail

A

false, it is built from tail to head. the last malonyl group added becomes C1 and C2. the original acetyl becomes C15 and C16

43
Q

How many rounds of fattyacid synthase-ACP addition do you need to make a 16:0 fatty acid?

A
  1. The first round adds 4 carbons together (the first malonyl and first acetyl), and then the next rounds add two carbons.
44
Q

What molecules activate fatty acid synthesis? deactivate?

A

EXCESS CITRATE AND INSULIN ACTIVATE FA synthesis. This means that you have enough glucose to be undergoing sugar metabolism (you are well fed), and you do not need to be burning your fats right now. You will undergo FA synthesis to store your fat for later.

EXCESSS PALMITOYL COA or GLUCAGON or EPINEPHRINE will DEACTIVATE fatty acid synthesis. Glucagon indicates starving conditions, meaning that your body will need to mobilize (break down) your fat stores, not store more fat. Epinephrine indicates fight or flight. your body does not need to be using energy making fatty acids when you are trying to run away from something.

45
Q

Outline the ATP differences between the catabolism of a 16:0 FA and the anabolism of a 16:0 FA. Do not include the krebs cycle

A

making acetyl coa–> 16:0 FA

  • activate acetyl coA to malonyl coA for 7 rounds of reduction (-7ATPS)
  • 7 cycles of addition (-14NADPH)

NET: -42-49 ATP
degrading 16:0 FA –> acetyl coA
-acetalize the FA chain (-2ATP)
- 7 rounds of beta oxidation (7 NADH, 7 FADH2)

NET: +33 ATP.

46
Q

What system is responsible for fatty acid elongation? Where does this occur? is ACP used in this system as an anchor? Out line the mechanism.

A

the fatty acid elongation system is responsible for fatty acid elongation. Instead of using ACP, Fatty acids are attached to coA.

refer to notes for mechanism. NADH reduces ketone to OH, NADPH reduces double bond to single bond

47
Q

How is an unsaturated fatty acid created?

A

the fatty acid is oxidized (-2e-) and NADPH is oxidized (also -2e-) to reduce O2, which makes H2O. This process utilizes cytochrome b and cytochrome b reductase (FADH2–> FAD+) to create the double bond.

48
Q

How is lysophosphatidic acid formed? draw the two ways this can be made.

A

when DHAP from glycolysis gets reduced with a fatty acid.

49
Q

How is lysophosphatidic acid converted into phosphatidic acid?

A

by adding another fatty acid to make phosphatidic acid.

50
Q

Insulin _____ Fatty acid synthesis in terms of regulation

A

insulin ACTIVATES fatty acid synthesis

51
Q

outline complete catabolism of propionyl coA

A 
propcoA to methmalonylcoA (-1ATP)
methmalonyl to succinyl coA
succinyl coA to succinate (+1GTP)
succinate to fumarate (+FADH2)
fumarate to malate 
malate to oxaloacetate (+NADH)
oxaloacetate to pyruvate (+1ATP)
pyruvate to acetyl coA (+1 NADH)
acetyl coa through krebs (+3 NADH, +1 FADH2, +1 GTP)
52
Q

What step of the tricarboxylate- transporter system is acetyl coA formed in the cytosol?

A

when citrate uses ATP to form oxaloacetate and acetyl coA

53
Q

Where does the conversion of pyruvate to oxaloacetate occur?

A

in the matrix of the mitochondria. This happens in the tricarboxylate transport system between the matrix (Where the krebs intermediates are) and the cytosol (where fatty acid synthesis is to take place)

CHEM- 3503 (8 decks)

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