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Biochemistry > Fatty Acid Synthesis > Flashcards

Fatty Acid Synthesis Flashcards

1
Q

how many carbons does palmitate have?

A

16 carbons

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2
Q

which part of the cell does fatty acid synthesis occur?

A

cytosol/cytoplasm

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3
Q

which organs does biosynthesis of FA happen?

A

liver, mammary gland, adipose tissue (mainly)

kidney, brain, lungs

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4
Q

where do we find acetylcoA?

A

mitochondria

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

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5
Q

what enzyme converts acetyl coA to citrate?

A

citrate synthase

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6
Q

phosphorylation of acetyl coA carboxylase

A

deactivation of the enzyme

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7
Q

dephosphorylation of acetyl coA carboxylase

A

activates the enzyme

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8
Q

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

A

fatty acids, triacylglycerols

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9
Q

co-factor requirements of FA synthesis

A

NADPH, ATP, manganese, biotin, HCO3

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10
Q

what is the immediate substrate of FA synthesis?

A

acetyl coA

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11
Q

what is the end product of FA synthesis ?

A

free palmitol

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12
Q

what is the initial and controlling step of FA synthesis?

A

production of malonyl coA

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13
Q

what provides all the carbon atoms in FA synthesis?

A

acetyl coA

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14
Q

acetyl coA is made from _____ in mitochondria

A

pyruvate

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15
Q

what enzyme converts pyruvate to acetyl coA in mitochondria?

A

pyruvate dehydrogenase

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16
Q

How does acetyl coA become available for FA synthesis?

A

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.

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17
Q

what condition activates ATP citrate lyase?

A

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

18
Q

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

A

decreased formation of citrate to acetyl coA for FA synthesis

19
Q

how is malonyl coA formed?

A

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

CO2 and ATP are used in this process.

20
Q

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

A

process of converting acetyl coA to malony coA

which is also the controlled step in the entire process

21
Q

what are the 3 sources of NADPH in FA synthesis?

A
  • PPP (major)
  • activity of malic enzyme (major)
  • activity of isocitrate dehydrogenase (minor)
22
Q

what enzyme assembles fatty acid chain in FA synthesis?

A

fatty acid synthase

23
Q

what counter-regulatory hormones deactivate acetyl coA carboxylase?

A

glucagon
epinephrine
catecholamines

24
Q

how is acetyl coA carboxylase regulated short-term?

A

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.

25
Q

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

A

long chain fatty acyl coA deactivates enzyme.

citrate activates enzyme.

26
Q

does insulin promote FA synthesis

A

yes b/c insulin normally is an ANABOLIC hormone

27
Q

long term regulation of Acetyl coA carboxylase

A

high-calorie/high carbohydrate diets

increased enzyme synthesis

28
Q

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

A

fatty acid synthase

29
Q

ACP contains _______ carrying intermediates of FA synthesis

A

phosphopantotheine moiety

30
Q

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

A

– SH group

31
Q

what is the first step fo FA elongation process?

A

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.

32
Q

2nd step of FA elongation

A

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

33
Q

3rd step of FA elongation

A

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

34
Q

4th step of FA elongation

A

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

35
Q

5th step of FA elongation

A

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

36
Q

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

A

thioesterase

37
Q

fates of free palmitate

A
  • esterification to acylglycerol
  • chain elongation /desaturation
  • esterification to cholesteryl esters (cholesterol)
38
Q

Stoichiometry of FA synthesis

A

Acetyl coA + 7 malonyl coA + 14 NADPH + 14 H+

—->

Palmitic + 7CO2 + 6H2O + 8 Coenz A + 14 NADP

39
Q

effect of insulin on intracellular cAMP

A

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

40
Q

what is effect of insulin in adipose tissue?

A

converts inactive form of pyruvate dehydrogenase to active form

Biochemistry (8 decks)

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