fatty acid synthesis (13)

Question 1

what organ are fatty acids synthesized in?

Answer 1

the liver

Question 2

when acetyl coA is in high concentration, what enzyme is inhibited?

Answer 2

pyruvate dehydrogenase

Question 3

what enzyme is inhibited when there are low levels of acetyl coA?

Answer 3

pyruvate carboxylase

Question 4

what enzyme cleaves citrate in the cytosol to acetyl coA and OAA?

Answer 4

citrate lyase

Question 5

where can the enzyme pyruvate dehydrogenase be found (what part of the cell)

Answer 5

ONLY in the mitochondria

Question 6

can acetyl coA cross the mitochondrial membrane?

Answer 6

HELLL NO

Question 7

what are the 2 sources of NADPH that is necessary for the synthesis of fatty acids?

Answer 7

1. recycling of OAA

2. pentose phosphate shunt

Question 8

what are the two steps of OAA recycling?

Answer 8

• OAA is reduced by an NADH dependent cytosolic malate dehydrogenase to malate
• Malate is then converted by the NADP+ dependent malic enzyme which oxidizes & decarboxylates malate to pyruvate

Question 9

what are the two enzymes necessary for fatty acid synthesis?

Answer 9

acetyl coA carboxylase-ACC

fatty acid synthase-FAS

Question 10

which enzyme is the rate controlling step in fatty acid synthesis?

Answer 10

ACC

Question 11

what reaction does ACC catalyze?

Answer 11

the addition of a carboxyl group from acetyl coA onto malonyl coA

Question 12

what is ACC’s cofactor?

Answer 12

biotin

Question 13

what does biotin bind in the presence of ATP during the ACC reaction?

Answer 13

binds CO2

Question 14

list the positive regulators of ACC (2)

Answer 14

• citrate causes ACC to polymerize (activates ACC)

- insulin stimulates phosphatase which dephosphorylates ACC to its active state)

Question 15

list the negative regulators of ACC (3)

Answer 15

• palmitoyl coA (feedback inhibition)
• glucagon & epinephrine phosphorylate ACC
• AMP (indicates low energy levels)

Question 16

what are the 5 steps of fatty acid synthesis

Answer 16

1. activation
2. condensation
3. reduction
4. dehydration
5. reduction

Question 17

what enzyme catalyzes step 1 of fatty acid synthesis?

Answer 17

ACC

Question 18

what enzyme catalyses steps 2-5 of fatty acid synthesis?

Answer 18

FAS

Question 19

what enzyme of fatty acid synthesis does this action describe?
“adds two carbon units form malonyl coA to the growing fatty acyl chain with the final product being palmitiate”

Answer 19

FAS

Question 20

describe what is happening in the 2nd step of fatty acid synthesis the condensation step

Answer 20

• acetyl group from acetyl coA first associates with the ACP phospho-pantetheinyl sulfhydryl group and then is transferred to the cysteine sulfhydryl of the other subunit
• malonyl from malonyl coA then associates with ACP phospho-pantetheinyl sulfhydryl group
• the malonyl and the acetyl groups condense with the release of the malonyl carboxyl group as CO2

Question 21

what is the product of the condensation step, step 2 of fatty acid synthesis?

Answer 21

a 4 carbon ß-keto acyl chain which is attached to the ACP phospho-pantetheinyl sulfhydryl group

Question 22

what step does the following describe

“reduction of the beta-keto group to an alcohol”

Answer 22

step 3, reduction step

Question 23

what molecule provides the reducing equivalents for steps 3 through 5?

Answer 23

NADPH

Question 24

where are fatty acids elongated (within the cell)

Answer 24

in the ER

Question 25

what is the major elongation that occurs in the body?

Answer 25

palmityl coA to sterayl coA (18 carbons)

Question 26

what is fatty acid desaturatoin?

Answer 26

the oxidation of fatty acids resulting in cis double bonds | it creates lipids of increasing structural and functional complexity with distinct biological roles

Question 27

where are desaturases located?

Answer 27

in the ER of a cell

Question 28

what 3 things do desaturases require?

Answer 28

O2, NADH and cytochrome b5

Question 29

what happens to desaturase activity during starvation?

Answer 29

their activity sharply decreases

Question 30

what happens to desaturase activity when large amounts of unsaturated fats are eaten?

Answer 30

desaturase activites descrease

Question 31

what 3 distinct desaturases do humans have?

Answer 31

∆9 desaturase ∆6 desaturase ∆5 desaturase

Question 32

what type of PUFAs does fish oil contain?

Answer 32

ω3 and ω6 PUFAs

Question 33

why isn't arachidonic acid considered an essential fatty acid?

Answer 33

because of linoleic acid is present (which is essential) the body can synthesize it

Question 34

list the 3 things that arachidonic acid is considered a substrate for

Answer 34

leukotrines, thromboxanes &prostaglandin

Question 35

name some things that eicosanoids are involved in

Answer 35

inflammatory response smooth muscle contraction brococonstriction/dilation

Question 36

what are the 3 pathways for eicosanoids syntheiss?

Answer 36

1. cyclic (cyclooxygenase) pathway 2. linear (lipoxygenase) pathway 3. cytochrome P450 pathway

Question 37

what does the cytochrome P450 pathway form?

Answer 37

epoxides

Question 38

what does the linear pathway form?

Answer 38

leukotrines, HETEs and lipoxins from a common intermediate HPETE

Question 39

what does the cyclic pathway form?

Answer 39

prostaglandins, throboxanes and prostacyclins

Question 40

what enzyme does aspirin and other NSAIDs act on?

Answer 40

COX enzyme

Question 41

what is the function of the COX enzyme?

Answer 41

convert arachidonic acid to PGH2

Question 42

COX1 or COX2 which does the following describe | " the consitiutive form expressed in all tissues"

Answer 42

cox1

Question 43

describe cox 2

Answer 43

the inducible form regulated by a variety of cytokines and growth factors increased in response to inflammation

Question 44

which of the following are irreversilbe/reversilbe inhibitors of COX1 and COX2 aspirin acetaminophren ibuprofen

Answer 44

aspirin- irreversible inhibitor acetaminophren- reversible inhibitor ibuprofen- reversible inhibitor