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Biochem 2 > Membrane Phospholipids > Flashcards

Membrane Phospholipids Flashcards

1
Q

Biosynthesis of membrane phospholipids begins with ________ or ________

A

Phosphatidic acid or DAG

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2
Q

In biosynthesis of membrane phospholipids, the head group is attached to ____ group

A

C-3 OH group

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3
Q

Biosynthesis of glycerol phospholipids, activation of 1,2 DAG or alcohol by _____

A

CTP

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4
Q

What are the activated intermediates in the biosynthesis of glycerophospholipids?

A

CDP-alcohol

CDP-1,2 DAG

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5
Q

Donation of a ______ from CDP- DAG to an alcohol

A

Phosphatidic acid

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6
Q

Donation of ________ group from CDP alcohol to 1,2 DAG

A

phosphomonoester

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7
Q

G3P is transported to the ER where it wil be converted to phosphatidate and from there will be converted to a phospholipids witht he addition of _______

A

Alcohol

*** for phospholipids synthesis either the phosphatidate or the alcohol must be activated by reaction with an NTP

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8
Q

Phospholipids are synthesized in the _______, transported to the _______, for additional synthesis

A

Smooth ER

Golgi complex

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9
Q

_________ must be inserted into specific membranes in specific proportions but cant diffuse bc they are nonpolar

A

Phospholipids

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10
Q

How are phospholipids transported to where they can be inserted into membrane?

A

Transported in membrane vesicles

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11
Q

Where is phospholipids A2 present in?

A

many mammalian tissues
pancreatic juice
Also present in snake and bee venoms

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12
Q

_______ secretions are especially rich in the phopsholipase A2 proenzyme

A

Pancreatic

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13
Q

What activates phospholipase A2?

A

Trypsin and bile salts

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14
Q

Phospholipase A2 sting on ______ releases archidonic acid (the precursor for ______)

A

Phosphatidylinositol

Prostaglandins

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15
Q

What is phoshopliapase A2 inhibited by?

A

Glucocorticoids (ex: cortisol)

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16
Q

_______ are short range hormones include prostaglandins, luekotrienes, and thromboxanes

A

Eicosanoids

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17
Q

Eicosanoids are created from _______ that’s incorporated into the phospholipids of membranes

A

Arachidonate 20:4

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18
Q

In response to hormone (stimuli) _______ is activated and attacks the C2 FA realeasing arachidonate

A

Phospholipase A2

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19
Q

Arachidonate can be synthesized from _____, _____ and _____

A

Phospholipids
DAG
And dietary linoleic acid

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20
Q

Prostaglandins are made by ___________

A

Prostaglandin H2 synthase (PGH2 synthase)

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21
Q

PHG2 synthase funciton in the _______

A

Smooth ER

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22
Q

What adds 2 O2 to form PGG2 in the synthesis of prostaglandins?

A

COX (PGH2 synthase’s cycloxygenase)

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23
Q

What converts peroxide to alcohol in prostaglandin synthesis to form PGH2?

A

PGH2 synthase peroxidase

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24
Q

_________ is precursor to other eicosanoids

A

PGH2

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25
Q

What are 2 examples of inhibits of cyclooxygenase activity of COX? (Prevents conversion of arachidonate to PGG2)

A

Aspirin and ibuprofen

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26
Q

________ catalyzes synthesis of prostaglandins that regulates GASTRIC MUCIN SECRETION

A

COX-1

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27
Q

_______ catalyzes synthesis of prostaglandins that mediate pain, inflammation and fever

A

COX-2

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28
Q

_______ inhibit both COX-1 and COX-2

A

NSAIDs (Apsirin, Ibuprofen, acetaminophen)

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29
Q

What are inhibitors that are specific for COX-2?

A

Celebrex and Vioxx

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30
Q

Aspirin is a(n) _________ inhibitor. It acetylates a ______ in the active site and blocks the active site in both COX isozymes

A

Irreversible

Serine

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31
Q

Ibuprofen and naproxen are ________ inhibitors. Resemble substrate, also block active site in BOTH enzymes

A

Competitive inhibitors

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32
Q

Aspirin, Ibuprofen, and naproxen are a few NSAIDs that inhibit ______________

A

PGH2 synthase

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33
Q

_______ developed to inhibit prostaglandin formation without harming the stomach

A

COX-2 specific inhibitors

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34
Q

What are some examples of COX-2 inhibitors?

A

Vioxx, Bextra, and Celebrex

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35
Q

__________ synthesis also begins with arachidonate

A

Leukotriene

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36
Q

O2 is added to arachidonate via ________

A

Lipoxygenases

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37
Q

_________ condense to form mevalonate in cholesterol synthesis step 1

A

3 acetate

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38
Q

Mevalonate converts to phosphorylated ________ in step 2 of cholesterol synthesis

A

5-C isoprene

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39
Q

_____________ polymerize to for the 30-C linear squalene in step 3 of cholesterol synthesis

A

Six isoprenes (5-C)

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40
Q

________ cyclizes to form the 4 rings that are modified to produce cholesterol

A

Squalene

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41
Q

Formation of mevalonate catalyzed by ________

A

HMG-CoA reductase

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42
Q

What is the rate limiting step of cholesterol synthesis?

A

Mevalonate

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43
Q

Bile acids assist in _________

A

Emulsification of fats

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44
Q

Bile is stored in the __________, secreted into ________ after a fatty meal

A

Gall bladder

SI

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45
Q

Bile acids such as ________ emulsify fats (surround droplets of fat to ioncrease Surface area for attack by lipases

A

Taurocholic acid

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46
Q

Cholesterol esters are more or less nonpolar than cholesterol?

A

More nonpolar

47
Q

What are the 4 major classes of lipoprotein particles?

A

Chylomicrons (largest and least dense)
VLDL
LDL
HDL (smallest and most dense)

48
Q

Chylomicrons and VLDL both mostly carry ________ but each come from different locations. _________ comes from the SI while ________ comes from the liver

A

TAGS
chylomicrons come from SI
VLDL come from liver

49
Q

LDL contains mostly ______

A

Cholesterol esters

50
Q

HDL contains mostly _________

A

Protein

51
Q

________ carries dietary fat front he small intestine to cells

A

Chylomicron

52
Q

_________ carries lipids made and taken up by the liver to cells

A

VLDL

53
Q

________ carries cholesterol made by the liver and from other sources to cells

A

LDL

54
Q

________ contributes to cholesterol removal from cells and inturn, excretion of it from the body

A

HDL

55
Q

_________ provide sites for the particle to bind to cell surface receptors, activate enzymes, etc.

A

Apolipoproteins

56
Q

What apoproteins are present on Chylomicrons

A

ApoB-48, ApoE, ApoC-II

57
Q

What apoprotein activates lipoprotein lipase To allow Free FA release for fuel in the capillaries of adipose tissue, heart and skeletal muscle?

A

ApoC-II

58
Q

What Apoprotein is present in the nascent Chylomicron from the small intestine?

A

Apoprotein B-48

59
Q

What lipoprotein does the nascent chylomicron which already has Apoprotein B-48 receive ApoC-II and ApoE from?

A

From HDL

60
Q

Extracellular lipoprotein lipase, activated by ______, degrades ______ in Chylomicrons

A

Apo C-II

TAG

61
Q

When chylomicrons are depleted of their TAG, “remnants” go to _______

A

Liver

62
Q

______ receptors in liver bind the remnants and take them up via ______

A

ApoE

Endocytosis

63
Q

Remnants of chylomicrons deposit their _______ in the liver

A

Cholesterol

64
Q

________ transport endogenous lipids

A

VLDL

65
Q

_______ and ______ from excess FA and cholesterol are packed into VLDL

A

Cholesterol esters and TAGs

66
Q

what apoproteins are present on VLDL? (5)

A 
ApoB-100
ApoC-1
ApoC-II
Apo-CIII
ApoE
67
Q

VLDLs take _____ to adipose and muscle

A

TAGs

68
Q

_______ take up the Free FA released via lipoprotein lipase from _____, reconvert them to _____ and store them in lipid droplets

A

Adipocytes
VLDL
Reconvert them to TAGs

69
Q

Muscles use the ______ for energy that is released from VLDL via ________

A

TAG; lipoprotein lipase

70
Q

What is the major apolipoprotein of LDL?

A

ApoB-100

71
Q

VLDL remnants become _____

A

LDL

72
Q

Removal of TAG from VLDL produces ______

A

LDL

73
Q

LDL is enriched in ________

A

Cholesterol/cholesterol esters

74
Q

________ carry cholesterol from liver to muscle and adipose tissue

A

LDLs

75
Q

_______ enable myocytes and adipocytes to take up cholesterol via receptor mediated endocytosis.

A

LDL receptors

76
Q

Familial hypercholesterolemia is associated with _________

A

LDL receptor mutations

77
Q

Mutations in ________ prevent normal uptake of LDL by liver and other tissues

A

LDL receptors

78
Q

Homozygous individuals with familial hypercholesterolemia have an increased risk of ________

A

Heart attack

79
Q

________ picks up cholesterol from non-liver tissues, including _____ cells at growing plaques

A

HDL

Foam cells

80
Q

What lipoprotein is involved in reverse cholesterol transport?

A

HDL

81
Q

ABC (ATP binding cassette transporters bring ______ from inside the cell to the plasma membrane

A

Cholesterol

82
Q

_________ carries cholesterol back to liver

A

HDL

83
Q

HDL proteins are _____ and _____

A

ApoA-1 and LCAT

84
Q

What is the function of LCAT present on HDL?

A

Catalyzes the formation of cholesterol esters from lecithin and cholesterol

85
Q

______ converts the cholesterol of chylomicron and VLDL remnants to cholesterol esters

A

LCAT

86
Q

There are 5 moves of regulation of cholesterol synthesis and transport:
______ of HMG-CoA reductase
______ of HMG-CoA gene
______ of HMG-CoA reductase
Activation of _______ which increases esterification for storage
Transcriptional regulation of the _______

A

Covalent modicaiton of HMG-CoA Reductase
Transcriptional regulation of HMG-CoA gene
Proteolytic degradation of HMG-CoA reductase
Activation of ACAT
Transcriptional regualtion of LDL receptors

87
Q

Insulin ________ HMG-CoA reductase

glucagon ______ HMG-CoA reductase

A

Insulin activates

Glucagon inhibits

88
Q

_______ stimulates proteolysis of HMG-CoA reductase and prevents the formation of ______

A

Oxysterol

Mevalonate

89
Q

When there is low ATP, ______ inhibits HMG-CoA reductase preventing the formation of ________

A

AMPK

Mevalonate

90
Q

_______ inhibits receptor mediated endocytosis of extracellular LDL-cholesterol

A

Oxysterol

91
Q

_____ stimulates the conversion of intracellular cholesterol to cholesterol esters

A

ACAT

92
Q

What is the transcription factor for HMG-CoA reductase?

A

SREBP

93
Q

SREBP-SCAP goes from the _______ to the ________, where it will be proteolytically cleaved into ____

A

ER to the Golgi, where it will be proteolytically cleaved into SREBP

94
Q

SREBP from the golgi will go to the nucleus where it will induce the transcription of _____ and lead to the synthesis of HMG-CoA reductase

A

SRE

95
Q

HMG-CoA reductase is active when _______ and inactive when ______

A

Dephosphorylated

Phosphorylated

96
Q

What phosphorylates HMG-CoA reductase to inactivate it?

A

AMPK

97
Q

HMG-CoA reductase is most active when

A

Dephosphorylated

98
Q

_________ of HMG-CoA reductase provides short term regulation

A

Covalent modification

99
Q

What 3 things lead to decreased activity of HMG-CoA reductase?

A

High AMP (which activates AMP dependent protein kinase)
Glucagon
Epinephrine

All lead to phosphorylation of HMG-CoA reductase

100
Q

Very high LDL-cholesterol levels tend to correlate with _______

A

Atherosclerosis

101
Q

High ________ cholesterol are negatively associated with heart disease

A

HDL

102
Q

_______ drugs inhibit HMG-CoA reductase to lower cholesterol

A

Statin

103
Q

Statins resemble _______ -> competitive inhibitors of HMG-CoA reductase

A

HMG-CoA

104
Q

In synthesis of bile salts in liver, it involves conversion of cholesterol to ________

A

Cholate

105
Q

Describe the activation of Cholate in the synthesis of bile salts in liver

A

Cholate + ATP + CoA to form Cholyl-CoA +AMP+ PPi

106
Q

In synthesis of bile salts in liver: Attachment of ______ to Cholyl-CoA forms glycochlate + CoA

A

Glycine

107
Q

In synthesis of bile salts in liver: Attachment of ______ to Cholyl-CoA forms Taurocholate + CoA

A

Taurine

108
Q

What are examples of bile salts

A

Glycocholate

Taurocholate

109
Q

What two amino acids are important in synthesis of bile salts?

A

Glycine or taurine

110
Q

What organelle are steroids made from cholesterol?

A

Mitochondria

111
Q

The side chain on _______ of the D ring is modified or cleaved in synthesis of steroids from cholesterol

A

C-17 of the D ring

112
Q

Steroids are made from cholesterol via ______, ______ and ______

A

Mixed-funciton oxidases
NADPH
Cytochrome P450 reductase

113
Q

Two adjacent hydroxylases groups on Carbons ____ and _____ in the synthesis of steroids from cholesterol

A

20 and 22

114
Q

_________ is important in synthesis of isoprenoids and can be made into over 20,000 additional products

A

Delta 3-Isopentenyl pyrophosphate

Biochem 2 (5 decks)

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