Fatty Acid Synthesis

Question 1

how many carbons does palmitate have?

Answer 1

16 carbons

Question 2

which part of the cell does fatty acid synthesis occur?

Answer 2

cytosol/cytoplasm

Question 3

which organs does biosynthesis of FA happen?

Answer 3

liver, mammary gland, adipose tissue (mainly)

kidney, brain, lungs

Question 4

where do we find acetylcoA?

Answer 4

mitochondria

acetylcoA will move into the cytoplasm - where FA synthesis occurs - as CITRATE!

Question 5

what enzyme converts acetyl coA to citrate?

Answer 5

citrate synthase

Question 6

phosphorylation of acetyl coA carboxylase

Answer 6

deactivation of the enzyme

Question 7

dephosphorylation of acetyl coA carboxylase

Answer 7

activates the enzyme

Question 8

excess carbs, proteins, and other molec obtained from body can be turned to ____ and stored as _____/

Answer 8

fatty acids, triacylglycerols

Question 9

co-factor requirements of FA synthesis

Answer 9

NADPH, ATP, manganese, biotin, HCO3

Question 10

what is the immediate substrate of FA synthesis?

Answer 10

acetyl coA

Question 11

what is the end product of FA synthesis ?

Answer 11

free palmitol

Question 12

what is the initial and controlling step of FA synthesis?

Answer 12

production of malonyl coA

Question 13

what provides all the carbon atoms in FA synthesis?

Answer 13

acetyl coA

Question 14

acetyl coA is made from _____ in mitochondria

Answer 14

pyruvate

Question 15

what enzyme converts pyruvate to acetyl coA in mitochondria?

Answer 15

pyruvate dehydrogenase

Question 16

How does acetyl coA become available for FA synthesis?

Answer 16

acetyl coA moves out from mitochondria and into cytoplasm as CITRATE while being co-transported w/ malate.

Citrate is then further cleaved by ATP CITRATE LYASE w/ utilization of energy & addition of coA – forming ACETYL COA.

Question 17

what condition activates ATP citrate lyase?

Answer 17

well-fed state (more substrates available for FA synthesis)

Question 18

what is the effect of the inhibition of ATP citrate lyase?

Answer 18

decreased formation of citrate to acetyl coA for FA synthesis

Question 19

how is malonyl coA formed?

Answer 19

acetyl coA undergoes carboxylation by acetyl coA carboxylase into malonyl coA.

CO2 and ATP are used in this process.

Question 20

what step in FA synthesis do biotin and HCO3 get to work?

Answer 20

process of converting acetyl coA to malony coA

which is also the controlled step in the entire process

Question 21

what are the 3 sources of NADPH in FA synthesis?

Answer 21

• PPP (major)
• activity of malic enzyme (major)
• activity of isocitrate dehydrogenase (minor)

Question 22

what enzyme assembles fatty acid chain in FA synthesis?

Answer 22

fatty acid synthase

Question 23

what counter-regulatory hormones deactivate acetyl coA carboxylase?

Answer 23

glucagon
epinephrine
catecholamines

Question 24

how is acetyl coA carboxylase regulated short-term?

Answer 24

through hormones

counter-regulatory hormones phosphorylate acetyl coA carboxylase leading to its deactivation.

INSULIN, on the contrary, dephosphorylates acetyl coA carboxylase leading to its activation.

Question 25

what is the effect of long chain fatty acyl coA and citrate on acetyl coA carboxylase?

Answer 25

long chain fatty acyl coA deactivates enzyme. citrate activates enzyme.

Question 26

does insulin promote FA synthesis

Answer 26

yes b/c insulin normally is an ANABOLIC hormone

Question 27

long term regulation of Acetyl coA carboxylase

Answer 27

high-calorie/high carbohydrate diets increased enzyme synthesis

Question 28

a multienzyme complex of one polypeptide chain w/ 7 separate enzyme activities & an acyl carrier protein

Answer 28

fatty acid synthase

Question 29

ACP contains _______ carrying intermediates of FA synthesis

Answer 29

phosphopantotheine moiety

Question 30

what part of ACP do acetyl coA and malonyl groups esterify?

Answer 30

-- SH group

Question 31

what is the first step fo FA elongation process?

Answer 31

a. acetyl coA combine w/ -- SH group (nz. Acetyl transcyclase) b. malonyl combines w/ --SH group on phosphopantotheine of ACP (nz. Malonyl transcyclase) forming 5-carbon ACYL-MALONYL enzyme.

Question 32

2nd step of FA elongation

Answer 32

decarboxylation of acyl-malonyl enzyme into 3-ketoacyl enzyme/ acetoacetyl enzyme (nz. 3-ketoacyl synthase_

Question 33

3rd step of FA elongation

Answer 33

reduction of acetoacetyl enzyme --> D(-)-3-hydroxyacyl enzyme (nz. 3-ketoacyl reductase)

Question 34

4th step of FA elongation

Answer 34

dehydration of D(-)-3-hydroxyacyl enzyme --> 2,3 unsaturated acyl enzyme (nz. hydratase)

Question 35

5th step of FA elongation

Answer 35

reduction of 2,3 unsaturated acyl enzyme --> acyl enzyme (nz. enoyl reductase)

Question 36

after the FA is synthesized, what enzyme is responsible for its release?

Answer 36

thioesterase

Question 37

fates of free palmitate

Answer 37

- esterification to acylglycerol - chain elongation /desaturation - esterification to cholesteryl esters (cholesterol)

Question 38

Stoichiometry of FA synthesis

Answer 38

Acetyl coA + 7 malonyl coA + 14 NADPH + 14 H+ ----> Palmitic + 7CO2 + 6H2O + 8 Coenz A + 14 NADP

Question 39

effect of insulin on intracellular cAMP

Answer 39

decreases intracellular cAMP level ---> LYPOLYSIS INHIBITED in adipose tissue --> decreased concentration of plasma FFA and long chain acyl coA

Question 40

what is effect of insulin in adipose tissue?

Answer 40

converts inactive form of pyruvate dehydrogenase to active form