lipids synthesis

Question 1

how long can FA be made

Answer 1

up to 36 carbons can be made in vivo but they all originate from the same precursor- the C16 FA palmitate

Question 2

where does palmiate synthesis take place

Answer 2

in the cytosol

Question 3

what creates the palmitate FA

Answer 3

the single multifunctional enzyme
fatty acid synthase (FAS)

Question 4

The synthesis of long-chained fatty acids
(C18 and higher) occurs where

Answer 4

in the endoplasmic
reticulum and mitochondria

Question 5

The synthesis of long-chained saturated
fatty acids from palmitate requires:

Answer 5

– palmitoyl-CoA (aka “activated” palmitate)
– malonyl-CoA (endoplasmic reticulum) or
acetyl-CoA (mitochondria)
– NADH or NADPH, plus H +
– 4 individual enzymes (rather than one enzyme
as with palmitate synthesis)

Question 6

what are the steps to fatty acyl Co-A elongation

Answer 6

1. condensation
2. reduction
3. dehydration
4. reductino

Question 7

what enzyme does condensation step

Answer 7

fatty acid elongase

Question 8

what enzyme does the first reduction step

Answer 8

B-keto acyl CoA reductase

Question 9

what enzyme does the dehydratino step

Answer 9

B-hydroxy acyl CoA dehydrase

Question 10

what enzyme does the second reduction

Answer 10

2 trans enoyl CoA reducatase

Question 11

what is the final step of fatty acyl CoA elongation

Answer 11

The final step involves either the action of thioesterase on the elongated fatty acyl- CoA (liberating the new fatty acid and CoA-SH), or the further elongation or desaturation of the elongated fatty acyl- CoA

Question 12

what enzyme carries out elongation of very long chained fatty acids

Answer 12

Elovl- previously termed fatty acid elongase, condense malonyl-CoA and acetyl-CoA with a fatty acyl-CoA
* To date, there are 7 Elovl’s
– Elovl1, Elovl2… Elovl7

Question 13

how are the Elovl’s categorized

Answer 13

The Elovl’s are divided into three classes:
– Elongation of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA):

– Elongation of polyunsaturated fatty acids
(PUFA):

– Elongation of specific fatty acids:

Question 14

what carries our the Elongation of saturated fatty acids (SFA) and
monounsaturated fatty acids (MUFA):

Answer 14

Elovl1, Elovl3, and Elovl6

Question 15

what carries out the Elongation of polyunsaturated fatty acids
(PUFA):

Answer 15

Elovl2 and Elovl4

Question 16

what carries out the elongation of specific fatty acids

Answer 16

Elovl5 and Elovl7

Question 17

what does the unsaturation of fatty acid require

Answer 17

the fatty acyl-CoA desaturases

Question 18

what desaturases are there in mammals

Answer 18

– ∆5 desaturase
– ∆6 desaturase
– ∆9 desaturase or stearoyl-CoA desaturase
(SCD)
* 5 isozymes exist: SCD1, SCD2… SCD5

Question 19

With very few exceptions, the desaturation
(or the introduction of a carbon-carbon
double bond by reduction) of a saturated
fatty acyl-CoA is introduced at the

Answer 19

9 th
carbon from the carboxylic acid (with the
carbon at C=O being #1)

Question 20

where can insects desaturate sites

Answer 20

delta 5, 6, 9, 12, 15

Question 21

wherecan lower plants desaturate fatty acids

Answer 21

delta 6, 9, 12, 15

Question 22

where can animals desaturate fatty acids

Answer 22

delta 4, 5, 6, 9

Question 23

where can plants desaturate fatty acids

Answer 23

delta 9, 12, 15

Question 24

what are the essential fatty acids that cannot be syntheszed by mammals

Answer 24

Linoleate (18:2(∆9,12 ) or 18:2n6)
α-linolenate (18:3(∆9,12,15 ) or 18:3n-3)

Question 25

how do plants generate omega 3 and omega 6 fatty acids

Answer 25

Plants have ∆12 and ∆15 desaturases

Question 26

what can linoleate and a- linolenate be used for

Answer 26

Linoleate and α-linolenate can be used by
mammals to make key omega-3 and -6
lipids that exhibit many functions in vivo

Question 27

functions of fatty acids

Answer 27

-stored as a component of TG, PL, an CE
-providing up to 14 ATP for every pair of carbons during
β-oxidaton
-have several beneficial and detrimental functions in vivo

Question 28

how is the gene expression of SCD1 regulated

Answer 28

by the cellular levels of cholesterol and
polyunsaturated fatty acids (PUFA)

Question 29

effect of high and low cholesterol on SCD1

Answer 29

High cholesterol levels inhibit the expression
of SCD1 whereas low cholesterol levels
increase the expression of SCD1

Question 30

how does high levels of PUFA affect expression of SCD1

Answer 30

High PUFA levels also inhibits the expression
of SCD1

Question 31

how is the mRNA of SCD1 regulated

Answer 31

by cellular fatty acids

Question 32

effect of stearate and oleate on SCD1 transcript

Answer 32

Stearate and oleate have no effect on the
half-life of the SCD1 transcript (of 8h)

Question 33

effect of arachidonate on SCD1

Answer 33

Arachidonate uniquely reduces the half-life of
the SCD1 transcript from 8h to 4h

Question 34

starvation effect on SCD1 activity

Answer 34

diminished

Question 35

uncotrolled type 1 diabetes effect on SCD1 activity

Answer 35

diminished

Question 36

how is SCD1 expression altered with dietary sources of n-3 and n-6 fatty acids (as free FA or assocaited with TG/PL)

Answer 36

they repress the expression of SCD1

Question 37

what are the dietary soruces of n-3 and n-6 FA that alter the expressino of SCD1

Answer 37

18:2n-6
18:3n-3
20:4n-6
20:5n-3
22:6n-6

Question 38

how do diets with high carb levels affect SCD1 activity

Answer 38

induce it

Question 39

how do diets with insulin administration affect SCD1 activity

Answer 39

induce it

Question 40

how do diets rich in SFA affect SCD1 levels

Answer 40

elevate it