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intro bch > Lipid Chemistry And Membranes > Flashcards

Lipid Chemistry And Membranes Flashcards

1
Q

What are lipids?

A

A large and heterogeneous group of substances of biological origin which are soluble in nonpolar solvents only. They include esters of fatty acids and glycerol or substances that yield them on hydrolysis.

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2
Q

Why are lipids only partially soluble in water or insoluble?

A

Due to the lack of polarizing atoms

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3
Q

Functions of lipids

A
  • Fat and oil store energy.
  • Phospholipids and sterols make up biological membranes
  • Some are enzyme cofactors, hydrophobic anchors for proteins eg, GPI anchores
  • Emulsifying agents, eg bile
  • Signalling molecules, eg hormones and intracellular messengers
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4
Q

Classes of lipids based on structure

A
  • Simple and Complex
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5
Q

Groups of lipids

A 
Fat and oil
Neutral fat (Triacylglycerol) Phospholipids Sphingolipids
Glycolipids
Waxes
Terpenoids (Carotenoids)
Steroids (Cholesterol)
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6
Q

Other classes of lipids

A
  • Storage, Structural, Signal Molecules

- FNPSGWTS (For No Person Sees God Without The Son)

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7
Q

What are simple lipids?

A

Lipids that yield fatty acids and alcohol on hydrolysis

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8
Q

What are complex lipids?

A

Lipids which may contain phosphate various carbohydrates and nitrogenous components such as sphingosine, ethanolamine, serine, hexosamines

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9
Q

Fat and oil are derivatives of fatty acids, true or false?

A

True

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10
Q

What are the universally stored forms of energy in living organisms?

A

Fats and oil

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11
Q

Amphipatic nature of fat and oil

A

They have both hydrophilic and hydrophobic parts.

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12
Q

Physiologic roles of fat and oil

A
  • Building blocks of phospholipids and glycolipids.
  • Modify proteins by covalent attachment and target them to their membrane location
  • Fuel molecules are stored as triacylglycerol which are uncharged esters of glycerol
  • Serve as hormones and intracellular messengers
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13
Q

How many carbons make up a fatty acid?

A

4 to 36

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14
Q

What kinds of acids are fatty acids?

A

Carboxylic acids with hydrocarbon chains

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15
Q

Functional group of fatty acids

A

Carboxyl group with formula R-COOH, named with ‘oic’

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16
Q

Types of fatty acids

A

Saturated - Unbranched, single bond

Unsaturated - Double bonds

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17
Q

Most fatty acids have even number of carbon atoms, true or false?

A

True

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18
Q

What is responsible for the even or odd number of carbon atoms in fatty acids?

A

They are synthesized from two carbon unit

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19
Q

Which fatty acids are the most abundant in animal tissues?

A

Saturated fatty acids

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20
Q

Examples of saturated fatty acids

A

Steric acid
Myristic acid
Palmitic acid
Arachidonic acid

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21
Q

What about the melting point and boiling point of saturated fatty acids?

A

It increases with increase in chain length

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22
Q

What about solubility of saturated fatty acids?

A

Solubility decreases with increasing chain length.

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23
Q

Number of chains of saturated fatty acids

A

Saturated fatty acids are usually between 2 -10 chain lengths and are solids at room temperature

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24
Q

Saturated fatty acids are most abundant in…

A

…animal tissues

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25
Q

What are the sources of unsaturated fatty acids?

A

Plants

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26
Q

Which packs better? Saturated or unsaturated fatty acids?

A

Saturated

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27
Q

What is the result of unsaturated fatty acids not packing well?

A

Intermolecular forces between molecules are lower so they’re easy to separate by raising the temperature.

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28
Q

What about the melting point of unsaturated fatty acids?

A

Lower

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29
Q

The configuration of the double bonds of most naturally occurring unsaturated fatty acids is in the…

A

…‘cis’ configuration.

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30
Q

‘Trans’ fatty acids are produced by…

A
  • fermentation in the rumen of dairy animals and are obtained from dairy products and meat
  • hydrogenation of fish or vegetable oils.
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31
Q

Effect of trans fatty acids

A
  • Trans configuration at double bonds causing molecule to straighten
  • No kinks in hydrocarbon chain
  • Behave like saturated
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32
Q

Is there a lower melting point in trans fatty acids?

A

No, since they behave like saturated

33
Q

What influences the melting point of a fatty acid?

A

Length of hydrocarbon chain

34
Q

Clinical effects of trans fatty acid.

A

Diets high in ‘trans’ fatty acids, correlate with increased blood levels of low density lipoprotein, leading to cardiovascular diseases

35
Q

At room temperature, all unsaturated fatty acids are..:

A

…liquid

36
Q

What are neutral fats?

A

Also known as triacylglycerol, they are esters of fatty acids and trihydric alcohol glycerol.

37
Q

Which types of lipids are the most abundant in nature?

A

Neutral fats, triacylglycerol

38
Q

The state of a triglycerol is determined by:

A

How the fatty acid chains it contains behaves

39
Q

Where one or two fatty acids are esterified with glycerol, we have…

A

…Mono- and Di-acylglycerols

40
Q

Usefulness of neutral fats

A
  • Energy storage, especially during starvation

- Insulation

41
Q

Examples of amphipathic molecules

A

Fatty acids

Phospholipids

42
Q

What are phospholipids?

A

Phospholipids are polar, ionic lipids composed of 1,2-diacylglycerol and a phosphordiester bridge that links the glycerol backbone to some base, usually a nitrogenous one, such as choline, serine or ethanolamine.

43
Q

The most abundant phospholipids in human in human tissues are…

A

… phosphatidyl choline (also called lecithin), phosphatidyl ethanolamine, and phosphatidyl serine.

44
Q

Phospholipids are:

A
  • components of bile
  • proteins anchors in membrane
  • signal mediators
  • components of lung surfactant
  • components of lipoproteins
45
Q

Sphingolipids are…

A

…complex lipids whose core structure is provided by the chain amino alcohol, sphingosine.

46
Q

Sphingolipids are present in large amounts in…

A

…the brain and nerve tissues, only a few are found as depot fat.

47
Q

The core structure of a natural sphingolipid is…

A

…ceramide

48
Q

Ceramide is formed…

A

…the attachment of unsaturated fatty or saturated fatty acids to sphingosine through its amino group

49
Q

The linkage between the amino group of the sphingosine and the fatty acid is…

A

…an amide linkage.

50
Q

Types of sphingolipids

A

Sphingomyelin
Cerebrosides
Gangliosides

51
Q

Sphingomyelin is a major structural lipid of membranes of nervous tissue. True or false?

A

True

52
Q

What is the only sphingolipid that is a phospholipid?

A

Sphingomyelin

53
Q

Structure of sphingolmyelin:

A
  • The primary alcohol at C-1 of sphingosine is esterified to choline
  • through a phosphodiester bridge
  • and the amino group of sphingosine is attached to a long chain fatty acid by an amide bond.
54
Q

What constitutes a sphingomyelin?

A

Ceramide + Phosphocholin group

55
Q

What are cerebrosides?

A

Cerebrosides are ceramide monohexosides .They contain Cerebronic acid, a C24 fatty acid linked to sphingosine by an amide linkage.
The term cerebroside usually refers to galactocerebroside, is also called GALACTOLIPID.

56
Q

The two most common cerebrosides are…

A

Galactocerebroside and Glucocerebroside.

57
Q

What is the major sulfolipid of the blame and accounts for approximately 15% of the lipids of the white matter?

A

Galactocerebrowside-3- sulphate

58
Q

Gangliosides are sphingoplipids found in…

A

The ganglia of nerve cells and the spleen

59
Q

Which shpingolipid contains sialic acid?

A

Gangliosides

60
Q

Functions of sphingolipids

A
  • The carbohydrate moieties of certain sphingolipids define the human blood groups so are key in blood transfusion
  • They are usually found in the outer surface of cell, where they present points of recognition for extracellular molecules or surfaces of neighbouring cells
  • They are important for organ and tissue specificities.
61
Q

Steroids are…

A

…structural lipids present in the membrane of most eukaryotic cells.

62
Q

What is the major sterol in animal tissues?

A

Cholesterol

63
Q

What is a sterol?

A

Steroid + Alcohol

64
Q

Structure of cholesterol

A

Cholesterol is amphipathic with a polar head group (the hydroxyl group at C-3) and a non-polar hydrocarbon body (the steroid nucleus and the hydrocarbon side chain at C-17) about as long as a 16- carbon fatty acid in its extended form.

65
Q

Function of cholesterol

A

It is an important component of cell membranes and is the basis for the synthesis of other steroids

66
Q

_____ is a precursor of bile acids

A

Cholesterol

67
Q

Cholesterol is present in high quantities in plants. True or false?

A

False, it is rarely present

68
Q

Which portion of cholesterol acts as an anchor that interacts with fatty acid chains of phospholipids?

A

Steroid portion

69
Q

What is the function of the hydroxyl group in cholesterol?

A

It binds it to phospholipids in the cell membrane.

70
Q

Steroids that are synthesized with cholesterols as the basis

A

Estradiol
Testosterone
Cortisone
Vitamin D

71
Q

Natural waxes are esters of…

A

…fatty acids and long chain alcohols

72
Q

Waxes characteristically consist of short alkyl chains, true or false?

A

False; the chains are long

73
Q

Functions of waxes

A

They serve as energy stores, waterproofing and lubrication

74
Q

Waxes can be found in…

A

…plants, animals and microbial tissues

75
Q

Terpenes’ basic structures follows a general principle of…

A

…2-methylbutane, usually referred to as isoprene units, (C5)n which build up the carbon skeleton of terpenes.

76
Q

Terpenes contain carbon atoms in multiples of

A

Five

77
Q

A terpene is made up of

A

Isoprene units

78
Q

Tetrapenes (C-40) are referred to as

A

Terpenoids

79
Q

Carotenoids are…

A

…terpenoids found in plant

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