Fatty Acid and TAG Synthesis Flashcards Preview

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Flashcards in Fatty Acid and TAG Synthesis Deck (35):
0

Essential fatty acids

Needed in diet
Linoleic acid 18:2(9,12)
Linolenic acid 18:3(9,12,15)
If Linoeic isn't around arachadonic is essential

1

Major sites of Fatty acid synth

Liver, lactating mammary gland

2

Minor sites of Fatty acid synth

Kidney adipose tissue

3

Coenzymes needed for FA Synth?

Acetyl CoA (pantothenic acid) ATP NADPH CO2

4

Where in the cell does FA synth take place?

Cytoplasm

5

How does acetyl CoA get to the cytoplasm

Citrate shuttle

6

When does FA synth take place?

When ATP is high and inhibits isocitrate dehydrogenase

7

How is citrate made from acetyl CoA?

Addition to oxaloacetate by citrate synthase

8

What enzyme catalyzes the rate limiting step of FA synth?

Acetyl CoA carboxylase (requires biotin) and 1 ATP per malonyl CoA formed

9

How is the active ACC different from the inactive?

Active is polymer
Inactive is dimer

10

Name one positive and one negative allosteric modifier of ACC.

+=citrate (substrate activation)
-=palmitoyl CoA (product inhibition)

11

How is ACC regulated hormonally?

Inactivated by phosphorylation (by glucagon, epinephrine, norepinephrine)

12

What effect does a high fat diet have on ACC? (Same as fasting and glucagon)

Down regulation, decreased synthesis of FA

13

What effect does a high carb fat free diet have on ACC?

Up regulated, more FA made

14

Step 1 of FA Synth

Acetyl CoA added to cysteine of condensing arm of FA synthase

15

Step 2 of FA synth?

Malonyl CoA added to ACP sulfhydryl group
(Takes 2 to tango; second substrate Added to A
Cuban Pedro)

16

Step 3 of FA synth?

Acetyl condensing group adds to malonyl acyl Carrier

17

Step 4 of FA synth?

Keto group is reduced (adds a hydroxyl group)

18

Step 5 of FA synth?

Dehydrated to make trans monounsaturated fatty acyl group

19

6th step of FA synth?

NADPH is used to reduce the double bond, leaving a saturated fatty acyl group to be transferred to the condensing enzyme SH

20

Mnemonic for FA synthase steps

Aaron Makes Terrible Remembering Devices...Not!

21

What enzyme releases palmitoyl-ACP from the FA synthase?

Thioesterase

22

Where does FA chain elongation occur?

ER

23

What double bonds can be formed by the three human fatty acid desaturases?

5, 6, or 9

24

What 3 things does the fatty acid desaturase system need?

Cytochrome b5
Desaturase
NADPH-cytochrome b5 reductase

25

Where can TAGs be made?

Liver and adipose tissue

26

TAG synthesis step one makes....

Lysophosphatidic acid (glycerol phosphate with 1 FA added)

27

Step 2 of TAG synthesis makes....

Phosphatidic acid (glycerol phosphate plus two FAs)

28

Step 3 of TAG synthesis makes....

DAG (by removing the phosphate to make room for a third FA to be added next)

29

Step 4 of TAG synthesis makes...

TAG!

30

What enzyme catalyzes each step of TAG synthesis?

1, 2, & 4 = acylytransferase
3= phosphatase

31

Where are chylomicrons made?

Intestinal mucous cells

32

**MT**
What is the cellular location of citrate lyase? What irreversible reaction does it catalyze?

Cytosol
Citrate + ATP ➡️ oxaloacetate+ Ac-CoA + ADP + Pi

33

**MT**
What is the cellular location and reaction catalyzes by the malic enzyme?

Malate + NADP ➡️ Pyruvate + CO2 + NADPH

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