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Biochemistry 2 > Final: fatty acid synthesis > Flashcards

Final: fatty acid synthesis Flashcards

1
Q

different forms of lipids

A

cholesterol, glycerol, phospholipids, fatty acids

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2
Q

simplest form of lipids

A

fatty acids

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3
Q

short and medium chain fatty acids

A

come from diet

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4
Q

long chain fatty acids

A

synthesized by liver and fat cells

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5
Q

how are long chain fatty acids synthesized?

A

combining lots of 2 carbon molecules (acetyl-CoA) into palmitoyl-CoA (single chain 16 carbon molecule

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6
Q

use of palmitoyl-CoA

A

use to synthesize even longer fatty acids

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7
Q

to create palmitoyl-CoA where do atoms come from?

A

acetyl-CoA provides carbon atoms

NADPH provides hydrogen atoms

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8
Q

where do we get acetyl-CoA for fatty acid synthesis

A

carbohydrate metabolism (mainly glucose)

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9
Q

after a starchy meal…

A

increase in glucose, pancreas releases insulin, cells take in glucose

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10
Q

inside cells…

A

glucose enters glycolysis, yields 2 pyruvate and ATP

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11
Q

pyruvate goes to…

A

mitochondria after pyruvate dehydrogenase converts it to acetyl-CoA

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12
Q

acetyl-CoA goes to…

A

CAC where it combines with oxaloacetate to form citrate

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13
Q

citrate goes to…

A

ETC to form ATP

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14
Q

more glucose =

A

more ATP

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15
Q

when CAC enzymes are inhibited, what do we use acetyl-CoA for?

A

fatty acid synthesis

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16
Q

where are enzymes for fatty acid synthesis found?

A

in the cytoplasm

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17
Q

how does acetyl-CoA get from mitochondria to cytoplasm?

A

acetyl-CoA combines with oxaloacetate to form citrate (just like in CAC)
happens when ATP is high

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18
Q

once in cytoplasm,

A

citrate lyase cleaves citrate into oxaloacetate and acetyl-CoA
citrate shuttle!

19
Q

citrate-malate shuttle…what does oxaloacetate do once in cytoplasm?

A

goes back to mitochondria to combine with the next acetyl-CoA
malic enzyme converts oxaloacetate to pyruvate (so it can cross to mito)
NADP+ to NADPH

20
Q

once back in mitochondria, pyruvate…

A

is converted back into oxaloacetate by pyruvate carboxylase

21
Q

what increases pyruvate carboxylase activity?

A

acetyl-CoA!

makes oxaloacetate more available

22
Q

what provides hydrogens for fatty acid synthesis?

A

some comes from NADPH produced by malic enzyme

the rest comes from metabolism of excess glucose in PPP

23
Q

fatty acid synthesis overview

A

acetyl-CoA to palmitoyl-CoA

24
Q

fatty acid synthesis rxn 1

A

acetyl-CoA to malonyl-CoA

enzyme: acetyl-CoA carboxylase

25
Q

acetyl-CoA carboxylase cofactors

A

ATP
Biotin
Carbon dioxide
ABC!

26
Q

rate-limiting step

A

acetyl-CoA carboxylase

27
Q

2 types of regulation of acetyl-CoA carboxylase

A

hormonal and allosteric regulation

28
Q

hormonal regulation of acetyl-CoA carboxylase

A

insulin (removes) and glucagon (adds) a phosphate group to acetyl-CoA carboxylase

29
Q

fed state

A

insulin activates phosphatase 2 which removes phosphate group from acetyl-CoA carboxylase, increasing activity

30
Q

fasted state

A

glucagon activates AMP-dependent kinase, adds phosphate group to acetyl-CoA carboxylase, decreasing activity
we want to use fatty acids for energy, not build them

31
Q

allosteric regulation

A

molecule increases or decreases activity of an enzyme by binding on a site different to where the substrate binds

32
Q

citrate and acetyl-CoA carboxylase

A

citrate allosterically increases activity of acetyl-CoA carboxylase

33
Q

fatty acids and acetyl-CoA carboxylase

A

fatty acids allosterically inhibit acetyl-CoA carboxylase

34
Q

1 cycle, what happens

A

1 acetyl-CoA to 1 malonyl-CoA

2 NADPH needed

35
Q

to make a 16 carbon palmitoyl-CoA we need…

A

8 acetyl-CoA

14 NADPH

36
Q

where are fatty acids stored

A

in adipocytes and liver cells as TAGs

37
Q

difference between fatty acid synthesis and beta-oxidation?

A

1) intermediates in fatty acid synthesis are covalently linked to sulfhydryl groups of ACP (acyl carrier proteins)
2) fatty acid synthesis occurs in cytosol
3) fatty acid synthase (FAS) is only protein in synthesis (it has many enzymatic activities)
4) synthesis uses NADP+/NADPH as co-enzyme for REDOX rxns

38
Q

what does it take to generate palmitate?

A

acetyl-CoA
7 malonyl-CoA (includes acetyl-CoA, CO2, ATP)
14 NADPH

39
Q

source of 2 carbon units during fatty acid synthesis?

A

malonyl-CoA

40
Q

how is malonyl-CoA produced?

A

by acetyl-CoA carboxylase

41
Q

acetyl-CoA carboxylase regulation

A

inhibited by palmitoyl-CoA and activated by citrate

42
Q

acetyl-CoA carboxylase regulation pt. 2

A

more active when not phosphorylated

less active when phosphorylated

43
Q

what happens to free fatty acids?

A

they don’t stay in cytosol!

they rapidly esterify and move in TAGs or membrane lipids

Biochemistry 2 (32 decks)

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