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BMSC 230 > Chapter 28 and 29 - Lipid Biosynthesis > Flashcards

Chapter 28 and 29 - Lipid Biosynthesis Flashcards

1
Q

fatty acid synthase (FAS)

A

a multi enzyme complex that synthesize fatty acids

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2
Q

FA chain length is increased by sequential addition of …

A

2-carbon units

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3
Q

elongation of FA stops with the formation of..

A

palmitate

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4
Q

site of fatty acid biosynthesis

A

cytosol

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5
Q

transport of acetyl CoA out of mitochondria in the form of..

A

citrate

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6
Q

ATP-citrate lyase

A

cleaves citrate at the cost of a molecule of ATP to yield cytoplasmic acetyl CoA and oxaloacetate

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7
Q

malonyl CoA

A

activated form of acetyl CoA

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8
Q

acetyl CoA carboxylase

A

catalyzes the first and rate limiting step of FA biosynthesis

  • carboxylation of acetyl CoA to malonyl CoA
  • irreversible
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9
Q

acetyl CoA carboxylase has a ______ prosthetic group

A

biotin

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10
Q

fatty acid synthase

A

a complex of distinct enzymes that data;yzes the synthesis of saturated long chain FA from acetyl CoA, malonyl CoA, and NADPH

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11
Q

fatty acid synthase in bacteria, plants

A

seven activities in seven separate polypeptides

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12
Q

fatty acid synthase in yeast

A

seven activities in two separate polypeptides

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13
Q

fatty acid synthase in vertebrates

A

seven activities in one large polypeptide

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14
Q

acetyl transacylase

A

catalyze the formation of acetyl ACP from Acetyl CoA

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15
Q

malonyl transacylase

A

catalyze the formation of malonyl ACP from malonyl-CoA

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16
Q

Intermediates of FA synthesis remain attached to FAS via…?

A

2 thiol groups

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17
Q

REVIEW

A

FAS steps

18
Q

FAS stops at ….

A

palmitate, 16C

19
Q

most fatty acids are long that…

A

palimatate.. 18-26C

20
Q

fatty acid elongation

A
  • occurs in ER

- 2 carbons added at a time from malonyl CoA

21
Q

how does fatty acid elongation work?

A

reactions use malonyl CoA to add two-carbon units sequentially to the carboxyl ends of both saturated and unsaturated acyl CoA substrates

22
Q

fatty acid desaturation

A

introduction of CIS double bonds

-catalyzed by desaturase enzymes (specific for location of double bond)

23
Q

Humans lack ___ and ___ desaturases.

A

delta12 and delta15; therefore, linoleate and a-linoleate are considered essential fatty acids

24
Q

Cholesterol is a lipid synthesized by virtually all cells, but especially…

A

liver

25
Q

functions of cholesterol

A
  • structural component of membranes

- precursor of bile salts, steroid hormones, and vit D.

26
Q

cholesterol structure

A
  • 27 carbons
  • all C-atoms come from acetyl CoA
  • synthesized in cytosol and ER
  • 4 fused rings, a hydrocarbon tail, -OH group on C3 and double bond at C5 and C6
27
Q

cholesterol biosynthetic pathways

A

acetyl CoA to cholesterol

  • 25 rxns
  • 4 stages
28
Q

step 1 of cholesterol biosynthetic pathway

A
  • synthesis of mevalonate
  • catalyzed by 3-hydroxy-3-methylglutaryl CoA reductase
  • irreversible
29
Q

Cholesterol is stored as….

A

cholesterol ester

30
Q

cholesterol is transported by…

A

lipoproteins

  • TA: chylomicrons and VLDL
  • cholesterols: LDL and HDL
31
Q

How is cholesterol synthesis regulated?

A
  • balance between synthesis and dietary uptake

- feedback inhibition by cholesterol

32
Q

famililal hypercholesterolemia

A
  • High cholesterol levels promote atherosclerosis
  • characterized by high concentrations of cholesterol and LDL in the plasma
  • cholesterol is deposited in various tissues because of the high concentration of LDL cholesterol in the plasma (defective LDL receptors)
33
Q

famililal hypercholesterolemia treatment

A

statins (cholesterol lowering drugs): competitive inhibitors of HMG CoA reductase

34
Q

acyltransferase

A

catalyze sequential attachment of fatty acids to glycerol backbone (ester bond)

35
Q

synthesis of phsophatidylcholine

A

liver possesses an enzyme, phosphatidylethanolamine methyltransferase, that synthesizes phosphatidylcholine from phosphatidylethanolamine when dietary choline is insufficient.

36
Q

eicosanoid

A
  • specialized fatty acids
  • signaling molecules, hormone-like actions
  • 20C polyunsaturated fatty acid (arachidonate)
37
Q

biological actions of eicosanoid

A

vasodilation, constriction, platelet aggregation, inhibition of platelet aggregation, contraction of smooth muscle, chemotaxis of leukocytes, release of lysosomal enzymes

38
Q

excess eicosanoid production symptoms

A

pain, inflammation, fever, nausea, vomiting

39
Q

phospholipase A2

A

release arachidonate

40
Q

eicosanoids are derived from..

A

arachidonate

41
Q

arachidonate

A

a 20:4 fatty acid derived from linoleate

-major precursor of several classes of signal molecules (prostaglandins, leukotrienes: called eicosanoids)

BMSC 230 (15 decks)

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