Fatty Acid and TAG Metabolism

Question 1

which two fatty acids cannot synthesize double bonds beyond the 9 Carbon position?

Answer 1

linoleic acid

alpha-linolenic acid

Question 2

How must we obtain linoleic acid and alpha-linolenic acid?

Answer 2

from diet

Question 3

what makes arachidonic acid?

Answer 3

linoleic acid

Question 4

what is the parent of all eicosanoids?

Answer 4

arachidonic acid (from linoleic acid)

Question 5

When is fatty acid synthesis and TAG synthesis most likely to occur?

Answer 5

during fed state

Question 6

what hormone promotes TAG and fatty acid synthesis?

Answer 6

insulin

Question 7

what is the prepretory step in fatty acid synthesis?

Answer 7

acetyl CoA is superactivated/prepped by making malonyl CoA

Question 8

where are the enzymes of FA synthesis located?

Answer 8

cytoplasm

Question 9

what does malic enzyme convert malate directly to?

Answer 9

pyruvate and removes CO2 and produces NADPH

Question 10

what does acetyl CoA carboxylsae (ACC) need?

Answer 10

CO2 and biotin

Question 11

what does citrate do the ACC?

Answer 11

activates allosterically (Short term)

Question 12

what does palmitoyl CoA do to ACC?

Answer 12

allosterically inhibits ACC

Question 13

what does phosphorylation on Ser/Thr residues through AMPK do to ACC?

Answer 13

inhibits ACC (hormonally)

Question 14

what causes phosphorylation of ACC?

Answer 14

glucagon / epinepherine

Question 15

when is ACC active?

Answer 15

dephosphorylated form

Question 16

what does insulin activate to make ACC active?

Answer 16

protein phosphatase

Question 17

FAS takes 1 malonyl CoA and adds how many carbons to it?

Answer 17

2

Question 18

what are the two forms of FAS?

Answer 18

dimer (active)

monomer

Question 19

how much energy is needed to synthesize FA?

Answer 19

7 ATP - to prep malonyl CoA

14 NADPHs - elongation steps

Question 20

what determines the overall rate of FA synthesis?

Answer 20

availability of malonyl CoA

Question 21

what energy source is important during elongation steps?

Answer 21

NADPH

Question 22

Every 2 C added in FA synthesis are added in the form of what?

Answer 22

malonyl CoA - uses 2 out of the 3 C (1 C gets kicked off)

Question 23

what are the 2 major roles of citrate?

Answer 23

allosteric activator of ACC

vehicle by which acetyl coA moves from mitochondria to cytoplasm

Question 24

what moves acetyl CoA from mitochondria to cytoplasm?

Answer 24

citrate

Question 25

where does chain elongation and desaturation occur?

Answer 25

ER

Question 26

what 3 things do you need for the desaturation of FA?

Answer 26

1. desaturase 2. cytochrome B5 3. cytochrome B5 reductase + NADPH

Question 27

what does elongation and desaturation allow us to do?

Answer 27

synthesize polysaturated FA from essentail FA

Question 28

what stimulates TAG synthesis from FA?

Answer 28

insulin

Question 29

what stimulates glycogen synthesis from glucose?

Answer 29

insulin

Question 30

which part of TAGs is essential for its storage?

Answer 30

glycerol backbone

Question 31

which tissues have glycerol phosphate?

Answer 31

adipose tissue | liver*

Question 32

what are 90% of FA in plasmas as?

Answer 32

fatty acid esters (TAGS, cholsteryl esters, phospholipids) in circulating lipoproteins

Question 33

where does unsaturated FA have double bonds?

Answer 33

3 C apart

Question 34

what introduces the kinks to unsaturated FA?

Answer 34

cis

Question 35

if linoleic acid is not supplied what becomes essential in diet?

Answer 35

arachidonic acid

Question 36

what are the precursors of FA synthesis?

Answer 36

acetyl CoA (pantothenic acid) ATP NADPH Co2

Question 37

what is a key intermediate between fat and carb metabolism?

Answer 37

Acetyl CoA

Question 38

what are the 3 pathways of FA synthesis?

Answer 38

1. synthesis of palmitate from Acetyl CoA 2. elongation of palmitate 3. desaturation

Question 39

where is acetyl CoA in mitochondria coming from?

Answer 39

oxidation of pyruvate (PDH complex)

Question 40

what does high ATP in the mitochondria inhibit?

Answer 40

isocitrate dehydrogenase

Question 41

what is the first committed step of FA synthesis?

Answer 41

Acetyl CoA carboxylase (ACC)

Question 42

what is the rate limiting enzyme for FA synthesis?

Answer 42

ACC

Question 43

what does the carboxylation of acetyl CoA to form malonyl CoA require as far as energy?

Answer 43

1 ATP per malonyl CoA formed!

Question 44

what are long term regulation of ACC that promote FA synthesis?

Answer 44

high carb and fat free diets - upregulation, induction

Question 45

what are long term regulation of ACC that decrease FA synthesis?

Answer 45

high fat diets, fasting, glucagon - down reg, repression

Question 46

what up regulates the amount of dimeric form of FAS expressed?

Answer 46

insulin

Question 47

what are the key regulators of Acetyl CoA carboxylase (ACC)?

Answer 47

citrate palmitoyl CoA/fatty acyl CoA Insulin Glucagon/Epinepherine

Question 48

where does FA elongation occur by reversal of Beta oxidation?

Answer 48

mitochondria (minor elongation pathway)

Question 49

where is the major elongation pathway taking place?

Answer 49

ER

Question 50

what are sites of unsaturation introduced to?

Answer 50

fatty acyl CoA desaturases that introduce double bonds to 5,6,9 position

Question 51

what are the essential FA?

Answer 51

linoleate linolenate *they have unsaturations beyond the 9 carbon

Question 52

what does the synthesis of polyunsaturated FA start with?

Answer 52

linolenic acid