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NPLEX - Biochemistry > Lipids > Flashcards

Lipids Flashcards

1
Q

When the liver has enough ATP, what does it do with the build-up of acetyl CoA?

A

it forms polymers of acetyl-CoA (fatty acids)

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2
Q

Are ketone bodies produced in a fed state or in a fasting state?

A

fasting

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3
Q

Name two key functions of thromboxanes.

A

coagulation, vasoconstriction

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4
Q

Bile acids (cholic acid and chenodeoxycholic acid) are synthesized in the liver from?

A

cholesterol

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5
Q

How many carbons are in linoleic acid? How many double bonds?

A

18:2

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6
Q

T/F: VLDL delivers hepatic triglycerides to peripheral tissues.

A

T

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7
Q

Where in the cell does beta-oxidation occur?

A

mitochondrial matrix

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8
Q

What is the biological significance of cardiolipin?

A

It serves as an insulator and stabilizes the activity of protein complexes important to the electron transport chain

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9
Q

Which enzyme converts arachidonic acid to leukotrienes?

A

lipoxygenase

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10
Q

What type of bond is formed between each fatty acid and the glycerol molecule in a triglyceride?

A

ester bonds

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11
Q

Where does the first double bond in linolenic acid occur?

A

third carbon from the methyl terminus

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12
Q

Type IIa hypercholesterolemia has increased levels of ___

A

LDL

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13
Q

Generally, when fatty acids are oxidized inside the mitochondria, how many carbons are removed per reaction?

A

two carbons

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14
Q

Lipoprotein functions: Which cells secrete chylomicrons?

A

intestinal epithelial cells

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15
Q

ApoE is located on all lipoproteins except ___.

A

LDL

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16
Q

Before leaving the liver, bile acids are conjugated in amide linkage to ___.

A

glycine (glycocholic acid) or taurine (taurochenodeoxycholic acid)

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17
Q

In fatty acid synthesis, which Kreb intermediate is translocated form the mitochondria to the cytosol to produce acetyl-CoA?

A

citrate

citrate is cleaved by citrate lyase to produce cytosolic acetyl-CoA and OAA

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18
Q

Does secretin get activated by low or high pH of intestinal contents?

A

low pH (chyme entering the intestine is acidic)

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19
Q

How many double bonds are in palmitic acid?

A

16:0

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20
Q

25-hydroxycholecalciferol is transported to the ___ of the kidneys where it can be hydroxylated by one of two enzymes to different forms of vitamin D.

A

proximal tubules

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21
Q

Where is lipoprotein lipase synthesized? What would a deficiency cause?

A

adipocytes and muscle cells

familial lipoprotein lipase deficiency (type I hyperlipoproteinemia) results in extremely high chylomicronemia

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22
Q

Name three cofactors required for the hydroxylation of vitamin D by 25-hydroxylase.

A

NADPH, O2, MG2+

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23
Q

Which shunt is the major supplier of NADPH for fatty acid synthesis?

A

hexose monophosphate shunt (pentose phosphate pathway)

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24
Q

Does insulin phosphorylate or dephosphorylate hormone sensitive lipase?

A

hormone sensitive lipase is dephosphorylated and becomes inactive

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25
Q

Is arachidonic acid a saturated or unsaturated fatty acid?

A

unsaturated (20:4)

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26
Q

Are triglycerides readily absorbed in the duodenum?

A

no

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27
Q

Does insulin activate or deactivate HMG-CoA reductase?

A

activate

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28
Q

List the six steps of cholesterol synthesis starting from acetyl-CoA.

A

acetyl-CoA to mevalonic acid to isoprene to squalene to lanosterol to cholesterol

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29
Q

HDL is screted from which two places?

A

liver, intestine

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30
Q

Where in the cell does steroid synthesis occur?

A

cytoplasm

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31
Q

apoA-1 and apoA-II are proteins located on?

A

HDL

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32
Q

Is stearic acid an unsaturated or saturated fatty acid?

A

saturated (found in many foods including red meat and peanuts)

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33
Q

Fatty acids are synthesized in the ___ of the cell.

A

cytosol

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34
Q

HDL - What is the major molecule it transports?

A

reverse cholesterol transport (from tissues to liver)

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35
Q

Fatty acid synthesis occurs in the ___ and beta oxidation occurs in the ___.

A

cytoplasm

mitochondria

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36
Q

Fatty acid entry into cytosol is via the ___.

A

citrate shuttle

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37
Q

What is the pathophysiology of type IIa hypercholesterolemia?

A

decreased number of LDL receptors

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38
Q

Name the five main functions of prostaglandins.

A

inflammation, pain, fever, tissue repair, clotting

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39
Q

What is the role of PIP2?

A

hormonal signal transmission via activated phospholipase C formation of inositol-3-P (IP3) and diacylglycerol (DAG), followed by mobilization of Ca2+ and activation of protein kinase C

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40
Q

What are two situations where ketone bodies are found in urine?

A

prolonged starvation, diabetic ketoacidosis

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41
Q

T/F: short and medium chain length FAs require micelles for absorption by the intestinal mucosa

A

F

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42
Q

Type III dysbetalipoproteinemia has altered apolipoprotein ___, and increased ___ and ___.

A

E, IDL, VLDL

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43
Q

Corticosteroids (cortisol) inhibit which enzyme involved in prostaglandin synthesis?

A

phospholipase A2

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44
Q

Do trans fats ever occur naturally in nature, or are they always synthesized?

A

trans fats do occur naturally

45
Q

Cholesterol synthesis: 2/3 of plasma cholesterol is esterified by ___.

A

lecithin-cholesterol acyltransferase (LCAT)

46
Q

What is the main function of apolipoprotein E?

A

mediates remnant (extra) uptake

47
Q

Thromboxane A2 is made from ___ and thromboxane A3 is made from ___.

A

TXA2 from arachidonic acid (AA) and TXA3 from eicosapentaenoic acid (EPA).

48
Q

What is the main function of apolipoprotein B-48?

A

mediates chylomicron secretion

49
Q

Name the five steps of fatty acid synthesis.

A

carboxylation, condensation, reduction, dehydration, reduction

50
Q

Lipoprotein lipase is involved in the storage of triacylglycerol. Name the enzyme that initiates mobilization of stored fat and removes a fatty acid from carbon 1 or 3 of the triacylglycerol.

A

hormone sensitive lipase

51
Q

Chylomicrons are released by exocytosis from intestinal mucosa and enter the blood via which vein located near the heart?

A

left subclavian vein

52
Q

Apolipoprotein B-100 binds to ___ receptors.

A

LDL

53
Q

HMG-CoA reductase catalyzes the rate-limiting step in cholesterol synthesis and inhibits the formation of?

A

mevalonic acid from HMG-CoA

54
Q

Type IIb combined hyperlipidemia has increased levels of ___ and ___.

A

LDL, VLDL

55
Q

Cholecalciferol is formed in the skin when UV light acts upon ___.

A

7-dehydrocholesterol

56
Q

LDL is taken up by target cells via what process?

A

receptor-mediated endocytosis

57
Q

Does EPI turn on or off the cAMP cascade leading to triacylglycerol degradation?

A

turned on (FA synthesis turned off)

58
Q

VLDL - What is the major molecule it transports?

A

delivers hepatic TG to tissues

59
Q

Which enzyme releases free fatty acids from triglycerides?

A

lipase

60
Q

LDL delivers hepatic cholesterol to ___.

A

peripheral tissues

61
Q

Type IV hypertriglyceridemia is caused by hepatic overproduction of ___.

A

VLDL

62
Q

Name the three products of the beta-oxidation of a fatty acid.

A

FADH2, NADH, acetyl-CoA

63
Q

What two factors influence the melting temperature of a fatty acid?

A

increasing chain length increasing melting temp

addition of double bounds decreases the melting temp

64
Q

What is the predominant fatty acid in olive oil? How many double bonds are in this fatty acid?

A

oleic acid

18:1 (omega-9)

65
Q

If removal of the chylomicron remnant is defective, what condition results? Which apo protein is defective?

A

familial type II hyperlipoproteinemia (aka dysbealipoproteinemia)

apoE

66
Q

Which enzyme converts arachidonic acid into prostaglandins?

A

cyclooxygenase

67
Q

The simplest glycerophospholipid is ___.

A

phosphatidic acid

68
Q

Which lipoproteins contain apoC-II?

A

chylomicrons, VLDL, HDL

69
Q

What is the rate-limiting step of cholesterol synthesis?

A

HMG-CoA reductase

70
Q

The side chains of bile salts contain which two amino acids?

A

glycine, taurine

71
Q

Fatty acids are degraded in the ___ of the cell.

A

mitochondria

72
Q

Which organ makes ketone bodies but cannot use them?

A

liver

73
Q

T/F: type V mixed hypertriglyceridemia has only increased VLDL.

A

F

increased VLDL and chylomicrons

74
Q

In fatty acid synthesis, acetyl-CoA via carboxylation forms ___.

A

malonyl-CoA

75
Q

Apolipoprotein C-II is a cofactor for which enzyme?

A

lipoprotein lipase

76
Q

How does a drug that lowers bile acids lower cholesterol?

A

when bile is removed, replacement bile must be synthesized from cholesterol, which lowers cholesterol

77
Q

Which phospholipid does not have a glycerol backbone and is abundant in neurons?

A

sphingomyelin

78
Q

HDL mediates transport of cholesterol from where to where?

A

periphery to liver (reverse cholesterol transport)

79
Q

Chylomicrons deliver dietary ___ to ___ and dietary ___ to ___.

A

triglycerides to peripheral tissues

cholesterol to liver

80
Q

Is the tail of a phospholipid hydrophilic or hydrophobic?

A

hydrophobic

81
Q

Cholecalciferol is hydroxylated in the liver to ___ by the enzyme ___.

A

25-hydroxycholecalciferol

25-hydroxylase

82
Q

Vitamin D is hydroxylated first in the ___ and then in the ___.

A

liver

kidney

83
Q

Fatty acid entry into mitochondria is via ___, which is inhibited by ___.

A

carnitine shuttle

cytoplasmic malonyl-CoA

84
Q

Of the 15-30g of bile salts secreted per day, ___ grams are lost in feces.

A

0.5

85
Q

Is the head of a phospholipid hydrophobic or hydrophilic?

A

hydrophilic

86
Q

Arrange the following in order of size (largest to smallest): LDL, IDL, HDL, VLDL, Chylomicron

A

Chylomicron, VLDL, IDL, LDL, HDL

87
Q

Apolipoprotein A-I activates ___.

A

activates LCAT

88
Q

In which part of the small intestine does the process of emulsification of dietary lipids begin?

A

duodenum

89
Q

LDL - What is the major molecule it transports?

A

delivers hepatic cholesterol to tissues

90
Q

Would high levels of malonyl-CoA increase or decrease the levels of acylcarnitine transferase I?

A

decrease

malonyl-CoA inhibits acylcarnitine transferase I

91
Q

Name the enzyme found in the mucosa of the jejunum and lower duodenum that causes gallbladder contractions in response to dietary lipids?

A

CCK - cholecystokinin

92
Q

Is oleic acid a mono- or polyunsaturated fatty acid?

A

mono

93
Q

Describe the composition of a triglyceride.

A

triglycerides are formed from a single molecule of glycerol, combined with three fatty acids on each of the OH groups

94
Q

Define the term amphipathic.

A

contains both hydrophobic and hydrophilic regions (ex: phospholipid)

95
Q

The enzyme 1-alpha-hydroxylase is activated by ___ to form the main biologically active vitamin D.

A

PTH

96
Q

Congenital abetalipoproteinemia occurs when triacylglycerols accumulate in the intestinal mucosa. Name the apo protein that is deficient.

A

Apo B-48

97
Q

Fatty acids are made by a multienzyme complex called ___.

A

fatty acid synthase

98
Q

In fatty acid synthesis, what is the enzyme that catalyzes the reaction of acetyl-CoA to malonyl-CoA?

A

acetyl-CoA carboxylase (biotin enzyme)

99
Q

Where is VLDL secreted from?

A

liver

100
Q

How many carbons are linolenic acid? How many double bonds?

A

18:3

101
Q

Excess lipids in the feces is termed ___.

A

steatorrhea

102
Q

What is the active carrier of choline?

A

CDP-choline

103
Q

Where does the digestion of lipids begin?

A

stomach

104
Q

Ketone bodies are metabolized by the brain to two molecules of ___.

A

acetyl-CoA

105
Q

Where is the cell acetyl-CoA generated?

A

cytosol

106
Q

The hormonally active form of vitamin D is also known as ___.

A

calcitriol

107
Q

Chylomicron - where is it secreted and what two main dietary substances does it transport?

A

delivers dietary TG to peripheral tissue and dietary cholesterol to liver

secreted by intestinal epithelium

108
Q

Name the four major families of eicosanoids.

A

leukotrienes (LTA), thromboxanes (TXA), prostacyclins (PGI), prostaglandins (PGE)

NPLEX - Biochemistry (8 decks)

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