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Biochemistry > Lipids > Flashcards

Lipids Flashcards

1
Q

What are the 2 structures that lipids can be broken down into?

A

fatty acids and isoprenoids

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2
Q

How do we name fatty acids? 2 methods.

A

:D^123

#= number of carbons
D= number of double bonds (db)
^123= 1st carbon of each db, counting from the acid end

OR

#= “ “
D= “ “
(omega - 3) = first carbon of first db counting from the methyl end, each subsequent db is then 3 carbons away

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3
Q

What are the 2 types of unsaturated fatty acids?

A

Cis and trans

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4
Q

Which form of unsaturated fats create a “bend” in the structure?

A

Cis

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5
Q

Does a bend in the structure increase or decrease membrane fluidity?

A

Increases

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6
Q

Do cis bonds allow for tighter or looser packing of phospholipids?

A

looser

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7
Q

Which type of unsaturated fats are mostly from naturally made fats?

A

cis

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8
Q

What are the 2 sources of trans fats?

A

1.) Some made naturally by gut bacteria of ruminants, meat.
2.) Most made commercially as a by-product of partial hydrogenation

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9
Q

Partially hydrogenation targets cis-bonds in fatty acids to:

A) Remove hydrogens and turn oils into solid fats
B) Remove hydrogens and turn solid fats into oils
C) Add hydrogens and turn oils into solid fats
D) Add hydrogens and turn solid fats into oils

A

C.) Add hydrogens and turn oils into solid fats

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10
Q

What is the by product of partial hydrogenation?

A

trans bonds

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11
Q

Less that how many grams per serving can be labelled as “0% trans fat”?

A

.5 g per serving

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12
Q

Where are fatty acids synthesized?

A

cytoplasm

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13
Q

Which fatty acid is usually synthesized? How many carbon?

A

16:0 palmitate

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14
Q

What are fatty acid substrates?

A

Acetyl CoA and malonyl CoA

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15
Q

Malonyl CoA is acetyl CoA with what extra group added?

A

CO2

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16
Q

With fatty acid synthase, how many fatty acid chains can be made at once?

A

2

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17
Q

What are 3 coenzymes that could be involved in FA synthesis?

A

B7, B5, B3

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18
Q

What does B7 (biotin) do in FAS?

A

Helps add CO2 to acetyl CoA to make malonyl CoA

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19
Q

What does B5 do in FAS?

A

Part of fatty acid synthase
Part of acetyl CoA and malonyl CoA

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20
Q

What does B3 do in FAS?

A

Reduced the FA chain

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21
Q

What are the steps of FA synthesis?

A

1.) acetyl group joins
2.) malonyl group joins
3.) acetyl and malonyl groups condense with loss of CO2
4.) O removed as water, NADPH donates H’s
5.) FA chain shifts over

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22
Q

If we can only make 2 FA chains at once, how do we get a 16 carbon chain?

A

Keep repeating steps 2-4

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23
Q

How do you separate the FA chain from the enzyme?

A

Use water to break the bond

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24
Q

How do you make a chain bigger than 16C? Where does this happen?

A

Elongate using enzymes embedded in the ER membrane. ER. Similar steps, different enzymes

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25
Q

How do you make odd-numbered fatty acid chains?

A

Start with propionyl CoA (3C) rather than acetyl CoA (2C) in step one can make odd number chains.

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26
Q

How do you get unsaturated FAs? (2)

A

1.) Made in ER: Desaturase enzymes use NAD(P)H (B3) to create double bonds
2.) Others are essential, from diet. (linoleic acid), plants

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27
Q

What do fatty acids support?

A

cardiovascular, immune, reproductive and nervous systems

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28
Q

What kind of fatty acid is alpha- linolenic acid?

A

Omega-3

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29
Q

What kind of fatty acid in linolenic acid?

A

Omega-6

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30
Q

What kind of il has a high level of linoleic acid?

A

vegetable oils

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31
Q

When is epinephrine released?

A

Sympathetic responses (flight or fight)

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32
Q

Synthesis is oppositely regulated to ______________.

A

breakdown

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33
Q

Glucagon promotes (beta ox / FA synthesis) and therefore (increases / decreases) FA synthesis.

A

beta ox
decreases

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34
Q

Insulin promotes (beta ox / FA synthesis) and therefore (increase / decrease) beta ox

A

FA synthesis, decreases

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35
Q

Epinephrine promotes (beta ox/FAS) and therefore decreases/increases FAS.

A

beta ox
decreases

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36
Q

What are the 3 regulators of fatty acid synthesis? And what do they do?

A

Glucagon and epinephrine (inhibit acetyl CoA carboxylase)

Insulin (activates acetyl CoA carboxylase)

37
Q

Acetyl CoA will be inhibited by phosphorus. True or False

A

True

38
Q

What are the 2 outcomes of the inhibition of acetyl CoA carboxylase, and the lowering of malonyl CoA

A

1.) decreased substrate for FA –> decreased FAS
2.) increased transport of FAs into the mitochondria –> increased beta oxidation

39
Q

Triglycerides are 3 fatty acids attached to a _____________ backbone via an _____________ link.

A

glycerol
ester

40
Q

What do FAs provide?

A

energy and insulation

41
Q

True or False. TGs pack tighter and therefore store energy more efficienty.

A

TGs

42
Q

Where does lipogenesis take place?

A

cytosol

43
Q

Steps of lipogenesis

A

1.) Addition of 2 FAs to a glycerol backbone
2.) Make substrates (glycerol-3-phosphate backbone and 3 fatty acyl CoAs)
3.) Transfer 2 FA chains to the backbone sequentially
4.) Replace the phosphate on the backbone with the 3rd FA chain

44
Q

What enzyme adds a phosphate to glycerol?

A

glycerol kinase

45
Q

In adipose and liver, what enzyme is used to convert DHAP to glycerol-3-phosphate using what enzyme?

A

glycerol-3-phosphate dehydrogenase

46
Q

What acts to carry the FA chains to the backbone and transfer them over from FA to fatty acyl CoA?

A

ATP

47
Q

What do both phospholipids and glycosphingolipids both contain what 3 things?

A

1.) a backbone
2.) lipid
3.) head group

48
Q

Phosphoglycerides contain what 2 things?

A

1.) glycerol backbone
2.) 2 fatty acid chains

49
Q

What 2 things do sphingolipids?

A

1.) sphingosine backbone
2.) ceramide: sphingosine (includes a fatty chain), plus and additional FA chain

50
Q

What are 3 sphingolipids?

A

1.) sphingomyelin
2.) cerebrosides
3.) gangliosides

51
Q

What are 2 phosoholipids?

A

1.) phosphatidates
2.) sphingomyelin

52
Q

What structures have a polar phosphate-alcohol head?

A

phospholipids

53
Q

What structures have a carbohydrate head?

A

glycosphingolipids

54
Q

What are the 3 major kinds of cell membrane lipids in animals?

A

glycolipids, phospholipids and cholesterol

55
Q

Where are phospholipids synthesized?

A

cytosol

56
Q

What 2 ways is glycerol-3-P made?

A

1.) Glycerol-3-phosphate is made from dihydroxyacetone phosphate (DHAP) in liver and adipose tissue.

2.) The liver can also convert glycerol into glycerol-3-phosphate.

57
Q

Once you have phosphatidic acid, how do you get to other phopholipids? What is added then removed in this process? What substitution is necessary?

A

1.) Phosphatidic acid is dephosphorylated

2.) Additional head groups are added: Different head groups are added to the remaining diacylglycerol (DAG) backbone

3.) CMP

4.) Nucleophilic

58
Q

What is the difference between the 2 phosolipid groups, glycerophospholipids and sphingomyelin?

A

It has a sphingosine back bone, rather than a glycerol backbone.

59
Q

What is the same between the 2 phospholipid groups?

A

both have 2 fatty acid-like tails

60
Q

What group do cerebrosides and gangliosides belong to?

A

sphingolipids (glycosphingolipids)

61
Q

What differentiates sphingomyelin and cerebrosides/gangliosides?

A

sm has a phosphorous head group
c/g have carbohydrate head group

G: 1 or more sialic acid PLUS 1 or more additional monosaccharide
C: monosaccharide head group
***sulfatide if additionally sulfated

62
Q

Which type of sphingolipid has a polar and nonpolar part?

A

Ganglioside

63
Q

What is sphingolipid storage disease (spingolipidases)? Most common example?

A

accumulation of sphingolipids
usually fatal by 5 years old
Tay-Sachs Disease
GM2 accumulates in lysosome due to enzyme deficiency
Most severe excesses occur in brain= neural cell damage

64
Q

What are eicosanoids derived from? (2)

A

1.) arachidonic acid (20:4)
2.) 20 C FAs

65
Q

What is a common eicosanoid?

A

prostaglandin

66
Q

What are 3 physiological functions of eicosanoids?

A

1.) vasodilation
2.) vasoconstriction
3.) platelet aggregation

67
Q

What is a mixture FAs linked to long-chain hydrocarbon alcohols via ester bonds?

A

wax (the simplest FA esters)
non polar

68
Q

What is an isoprene unit linked together called?

A

isoprene

69
Q

What forms could terpenes be?

A

alcohol, aldehyde, ring

70
Q

What is the smallest terpene? How many isoprene units?

A

monoterpene, 2

71
Q

What is a sesqui (1.5) terpene called?

A

Farnescene

72
Q

What is a triperpene called?

A

squalene

73
Q

What is a tetraterpene called?

A

beta cartene

74
Q

What is a mixed terpene?

A

terpene + non- terpene
ex: CoQ, vit K, farnesylated proteins

75
Q

How many isoprene units make up a steroid?

A

6 (4 fused rings with various substituents)

76
Q

What are steroids made from?

A

cholesterol

77
Q

Cholesterol synthesis starts with 3 of what molecule, making which intermediate?

A

acetyl-CoA into 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA)

78
Q

In cholesterol synthesis, what is the rate limiting enzyme? What does it do? What does high cholesterol do to this enzyme?

A

HMG-CoA reductase

catalyzes the conversion of HMG-CoA to mevalonate, a key step in the pathway. Regulation of HMG-CoA reductase is vital for maintaining cholesterol homeostasis in the body.

When cholesterol levels are elevated, it inhibits the activity of HMG-CoA reductase, thus reducing the production of cholesterol. This regulatory mechanism helps prevent excessive accumulation of cholesterol in cells.

79
Q

What class of pharma drugs inhibits this enzyme?

A

statins

80
Q

What isoprenoid is formed that is ultimately converted to the cyclic structure of cholesterol?

A

In the pathway of cholesterol synthesis, an isoprenoid called farnesyl pyrophosphate (FPP) is formed. FPP serves as a precursor for various molecules, including squalene. Squalene is then converted to lanosterol, which eventually leads to the formation of the cyclic structure of cholesterol.

81
Q

Cholesterol synthesis

A

1.) 3 A-COA
2.)HMG CoA
a.) ketogenesis
b.) rate limiting step
i.) HMG-CoA reductase begins synthesis
ii.) HMG- CoA r. blocked by high cholesterol levels or statin drugs
3.) mevalonate
4.) isopentenyl pyrophosphate (isoprene units)
5.) squalene
6.) cholesterol

82
Q

Where does most cholesterol synthesis occur?

A

liver

83
Q

What does the liver do with cholesterol?

A

1.) make bile
2.) make lipoproteins (LDL) to carry cholesterol to the tissues –> binds on cell and taken in –> broken down inside –> chol. released

84
Q

What is familial hypercholesteremia?

A

inherited defect in LDL-receptors (increase circulated LDL, therefore cholesterol in the blood
increase risk of myocardial infarction

85
Q

What is the precursor to steroid hormones?

A

cholesterol

86
Q

What is cholesterol first converted to, which is then converted to various other steroid hormones?

A

pregnenolone

87
Q

What can compete with intestinal cholesterol absorption? What do they help?

A

plant sterols
lower LDL cholesterol levels

88
Q

Cardiac glycosides are derivatives of what?

A

plant sterols

89
Q

What does digoxin do? (cardiac glycoside)

A

Increase heart contractility and decrease rate

Biochemistry (14 decks)

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