Fatty Acid Synthesis

Front 1

Where does de novo fatty acid synthesis occur?

Back 1

cytoplasm

Front 2

Where does elongation of existing fatty acids take place?

Back 2

mitochondria

Front 3

Where does desaturation of fatty acids occur?

Back 3

endoplasmic reticulum

Front 4

How does the Acetyl-CoA needed for fatty acid synthesis get from the mitochondria where it is formed to the cytoplasm?

Back 4

Acetyl CoA can't cross the mitochondrial membrane, but citrate can. Citrate is broken down into Acetyl-CoA and OAA by citrate lyase.

Front 5

What is the rate limiting step in de novo fatty acid synthesis?

Back 5

The conversion of Acetyl-CoA to malonyl CoA by Acetyl CoA carboxylase using 1 ATP, CO2 and a biotin cofactor.

Front 6

What reducing cofactor is used in de novo fatty acid synthesis? How is it's levels maintained in the cytoplasm?

Back 6

NADPH, Citrate -> OAA -> malate -> pyruvate + NADPH

Front 7

What inhibits Acetyl CoA carboxylase?

Back 7

palmitoyl CoA, phosphorylation by cAMP mediated protein kinases

Front 8

What stimulates Acetyl CoA carboxylase?

Back 8

citrate

Front 9

What is the effect of glucagon on fatty acid synthesis?

Back 9

inhibits fatty acid synthesis

Front 10

What is the effect of glucagon on beta oxidation? How?

Back 10

stimulates beta oxidation because it inhibits the formation of malonyl CoA which inhibits the carnitine palmitoyl transferase 1 needed for beta oxidation

Front 11

What enzymes are part of Fatty acid Synthetase complex (FAS)?

Back 11

acetyl transferase, malonyl transferase, beta-ketoacyl synthetase, beta-ketoacyl reductase, dehydratase, enoyl reductase

Front 12

What enzyme transfers acetyl CoA to the FAS complex?

Back 12

acetyl transferase

Front 13

What enzyme transfers malonyl CoA to the ACP-sulfhydryl on the FAS complex?

Back 13

malonyl transferase

Front 14

What is an ACP?

Back 14

acyl carrier protein

Front 15

What does beta-ketoacyl synthetase do?

Back 15

transfers the acetyl group on FAS to the alpha carbon of malonyl CoA on ACP displacing CO2

Front 16

What does beta-ketoacyl reductase do? What cofactor does it use?

Back 16

reduces the beta carbon producing beta hydroxybutyryl-S-ACP and oxidizing NADPH to NADP+

Front 17

What enzyme creates a double bond between the alpha and beta carbons of beta hydroxybutyryl-S-ACP?

Back 17

dehydratase

Front 18

What enzyme reduces the carbon double bond created by the dehydratase enzyme in fatty acid synthesis? Does it require a cofactor?

Back 18

Enoyl reductase, oxidizes NADPH to NADP+

Front 19

What is the last step in de novo fatty acid synthesis? What enzyme catalyzes it?

Back 19

a transferase shifts the newly formed acyl from the Sulfhydryl of ACP to the sulfhydryl of FAS, freeing it to accept another malonyl CoA molecule and continue elongation

Front 20

What is the longest fatty acid carbon chain that can be created by de novo fatty acid synthesis?

Back 20

Palmitic Acid (16:0)

Front 21

What does deacylase do?

Back 21

it removes the newly synthesised fatty acid from FAS so that FAS can be reused to synthesize more FAs

Front 22

How many CO2 are consumed to synthesize palmitic acid by de novo fatty acid synthesis?

Back 22

7 CO2 (one for every malonyl CoA formed and added to the growing fatty acid)

Front 23

How many NADPH are consumed per malonyl CoA added to the fatty acid chain?

Back 23

2 NADPH

Front 24

Which step of de novo fatty acid synthesis requires ATP?

Back 24

the formation of malonyl CoA from acetyl CoA via acetyl CoA carboxylase

Front 25

Name three pathways that generate NADPH.

Back 25

pentose phosphate pathway, isocitrate dehydrogenase, malic enzyme (malate -> pyruvate)

Front 26

Why does C75 Cerulenin drug inhibit hunger?

Back 26

it inhibits the fatty acid synthetase complex, thereby causing a buildup of malonyl CoA qhich either inhibits neuropeptide Y or other neuropeptides that stimulate hunger sensation in the brain

Front 27

fatty acid elongation in the mitochondria uses what precursor and adds what compound to it?

Back 27

starts with palmityl CoA and adds acetyl CoA

Front 28

Name the four enzymes involved in fatty acid elongation in order.

Back 28

thiolase, dehydrogenase, hydratase, dehydrogenase (reverse of beta oxidation pathway)

Front 29

the dehydrogenases in fatty acid elongation use what cofactor?

Back 29

NADPH (it gets oxidized)

Front 30

fatty acid elongation in the ER uses which compound as the 2 carbon donor?

Back 30

malonyl CoA

Front 31

What reaction does thiolase catalyze in fatty acid elongation?

Back 31

The transfer of palmitoyl CoA onto the alpha carbon of acetyl CoA.

Front 32

Under what conditions does fatty acid elongation occur?

Back 32

in the fed state

Front 33

why are linoleic and linolenic acids essential?

Back 33

because the mixed function oxidase used in the desaturation of fatty acids in the ER cannot add a double bond beyond the 9-10 carbons of fatty acids

Front 34

what enzyme adds double bonds to saturated fatty acids in the ER?

Back 34

mixed-function oxidase called desaturase

Front 35

does desaturase use a cofactor? which one?

Back 35

it oxidizes NADPH to NADP+

Front 36

what kind of double bond does desaturase create?

Back 36

cis

Front 37

what is the precursor of arachidonic acid?

Back 37

linoleic acid

Front 38

what is the precursor of docosahexaenoic acid?

Back 38

linolenic acid

Front 39

what pathway uses arachidonic acid as a substrate?

Back 39

prostaglandin synthesis

Front 40

what is docosahexaenoic acid used for?

Back 40

neuronal synapses and retinal photoreceptors