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Biological Chemistry > Lipids 2 > Flashcards

Lipids 2 Flashcards

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1
Q

What is Glycerolphospholipids composed of ?

A

Alcohol, Phosphate, Glycerol and 2 Fatty acids

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2
Q

Fatty acids form ester linkages with the first and second hydroxyl groups of ?

A

L-glycerol-3-phosphate

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3
Q

The phosphate group is ?

A

Charged at physiological pH

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4
Q

Where does biosynthesis of membrane phospholipids occur ?

A

In cytosol

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5
Q

Phospholipid head is attached to ? and by what ?

A

Phospholipid head is attached to diacylglycerol by a phosphodiester bond

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6
Q

PLA2 can release ?

A

Inflammatory mediators such as histamine, prostaglandins & leukotrienes

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7
Q

What happens in absence of strict regulation of PLA2 ?

A

A disproportionate release of inflammatory mediators can take place

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8
Q

What does Glucocorticoids upregulate ?

A

Lipocortin which inhibits PLA2 and reduce the inflammatory response

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9
Q

What is Lecithin ?

A

They are mixtures of glycerol phospholipids that contain the amino alcohol choline e.g. phosphatidylcholine

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10
Q

Where is Lecithin found ?

A

Found in egg yolks, wheat germ & soybeans

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11
Q

Lecithin is extracted and used as emulsifying agent in food because ? and what does this enable ?

A

Extracted & used as emulsifying agent in food because it has both polar & non-polar properties. This enables it to mix other fats & oils with water

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12
Q

What does Cephalin contain?

A

The amino alcohols serine or ethanolamine

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13
Q

Where are cephalins found?

A

Found in most cell membranes, particularly brain tissue (e.g. Phosphatidyl ethanolamine)

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14
Q

Cephalin is important in ?

A

The blood coagulation process, found in blood platelets (e.g. Phosphatidyl ethanolamine & Phosphatidyl serine work to increase thrombin)

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15
Q

Difference between Lecithin and Cephalin ?

A

Lecithin contains the amino alcohol - choline. Whereas, Cephalins contain the amino alcohol – ethanolamine (or serine)

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16
Q

Sphingolipids have a backbone of ?

A

Sphingosine (a derivative of ceramide)

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17
Q

Sphingosine is a ?

A

18-C amino alcohol with unsaturated hydrocarbon tail

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18
Q

What Sphingolipids contain?

A

Choline, Phosphate, Sphingosine (with built in hydrocarbon tail) and Fatty acid

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19
Q

Polar head group is connected to ?

A

Sphingosine by a glycosidic or phosphodiester linkage.

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20
Q

Where are Sphingolipids found ?

A

Found largely in the outer face of plasma membranes

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21
Q

Biological relevance of Sphingolipids ?

A
  • 60+ human sphingolipids identified in cell membranes
  • Prominent in neurons & cell recognition sites
  • Define human blood groups
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22
Q

Ceramide is the precursors to ?

A

Sphingolipids

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23
Q

What is Ceramide formed by?

A

Fatty acid attached to carbon 2 via an amide bond

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24
Q

What are Sphinglipidoses ?

A

They are disorders of sphingolipid metabolism Eg. Nieman-Picks disease

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25
Q

Ceramide + Water =

A

Fatty acid + Sphingosine

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26
Q

What are Sphingolipids subdivided into ?

A

Sphingomyelins, Glycosphingolipids (neutral glycolipids) and Gangliosides

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27
Q

Phosphatidylcholine (a glycerophospholipid) and sphingomyelin (a sphingolipid) have similar ?

A

3D structure & physical properties

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28
Q

What different roles to they plan in membranes ?

A

Sphingomyelin is abundant in myelin sheath that surrounds some nerve cells in animals

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29
Q

What is Glycosphingolipids subdivided into ?

A

Glycosphingolipids (Glycolipids) One or more sugars connected directly to the ceramide

  • Cerebrosides – 1 sugar
  • Globosides – 2+ sugars

Gangliosides Complex sphingolipids with oligosaccharide polar head & 1> sialic acid termini (-ve charge at pH7).

30
Q

Galactose + ceramide =

A

Galactocerebroside

31
Q

What does Cerebroside contain ?

A

Monosaccharides, Sphingosine (with attached hydrocarbon tail) and fatty acid

32
Q

What does Ganglioside contain ?

A

NANA (Sialic acid), Sugar(s), Sphingosine (with attached hydrocarbon tail) and fatty acid

33
Q

Where is the highest sialic acid concentration ? and why important role does it play ?

A

The brain has highest sialic acid concentration where it plays an important role in neural transmission & ganglioside structure

34
Q

What can Glycosphingolipids determine and using what part?

A

Blood groups (O, A, B) determined in part by oligosaccharide head group of glycosphingolipids

35
Q

Simply explain Fat (Triacylglycerols - TAGs) ?

A

Simplest storage lipids (energy source) constructed from fatty acids & alcohol

36
Q

What are lipids divided into?

A

Lipids that contain fatty acids (complex lipids)
- storage lipids: Triacylglycerols
- membrane lipids: Phospholipids & Glycolipids
Lipids that do not contain fatty acids e.g. cholesterol, vitamins, pigments.

37
Q

What is the advantage of fats over polysaccharides ?

A
  • Fatty acids carry more energy per carbon because they are more reduced.
  • Fatty acids carry less water per gram because they are nonpolar.
  • Glucose & glycogen are for short-term energy needs & quick delivery
  • Fats are for long-term (months) energy needs, good storage and slow delivery.
38
Q

Explain the structure of TAGs?

A
  • A triglyceride (TG, triacylglycerol – TAG or triacylglyceride) is an ester derived from glycerol & 3-4 Fatty Acids
  • All 3 hydroxyl groups of glycerol are esterified
  • Many different types: mainly division between saturated & unsaturated
  • The primary storage form of lipids (body fat)
  • Less soluble in water than FA due to esterification of carboxylate group
  • Less dense than water: fats & oils float
39
Q

High levels of triglycerides in the bloodstream have been linked to ?

A

Atherosclerosis and the risk of heart disease & stroke

40
Q

Properties of TAGs ?

A
  • Neutral (no ionic groups)
  • Non-polar & hydrophobic
  • Insoluble in water
  • Transported around the body shielded from water in plasma
  • Carried by large lipid particles the lipoproteins
  • Simple TAGs have 3 identical fatty acids esterified to glycerol backbone
  • Mixed TAGS have 2-3 differing fatty acids
41
Q

Basic structure of lipoprotein?

A

Non-polar lipid core containing TAG & cholesterol esters (cholesterol linked to fatty acid)

42
Q

5 classes of Lipoproteins by increasing density:

A
  1. Chylomicrons (CM)
  2. Very low density (VLDL)
  3. Intermediate density (IDL)
  4. Low density (LDL)
  5. High density (HD)
43
Q

What is are the TAGs & cholesterol esters surrounded by ?

A

Polar outer phospholipids shielding them from water

44
Q

What is used to synthesise their membranes ?

A

Cells use fats and cholesterol to synthesise their membranes

45
Q

TAGs cannot be absorbed by? but are broken into ?

A

TAGs cannot be absorbed by intestine, they are broken down into free fatty acids & glycerol by pancreatic lipase & colipase:
The activated complex works only at a water-fat interface
Must be emulsified by bile salts for excretion

46
Q

What is the main function of bile acid ?

A

The main function of bile acid is to facilitate the formation of micelles, which promotes the processing of dietary fat

47
Q

Bile salts are ?

A

Amphipathic molecules & very effective detergents

48
Q

What do Bile Salt act to solubilise ?

A

They act to solubilise dietary lipids & also the lipid-soluble vitamins A, D, E and K

49
Q

Soaps are ?

A

Salts of TAGs formed by breakdown in a strong base (saponification)

50
Q

Solubility in water and grease/oil in a long non-polar hydrophobic hydrocarbon chain ?

A

Insoluble in water but soluble in grease/oil

51
Q

Short polar carboxylate ion is? solubility in water and grease/oil ?

A

Short polar carboxylate ion is hydrophilic - water soluble but insoluble in grease/oil

52
Q

Non-polar tails dissolve in?

A

Grease/oil surrounding a dirt particle & disperse or emulsify the particles which are then washed away

53
Q

What are waxes ?

A

Carboxylic acid esters of long chain (C14-C36) saturated & unsaturated fatty acids with long chain alcohols (C16-C30)

54
Q

Insoluble with high melting points involved in:

A
  • storage of metabolic fuel in plankton
  • protection & pliability for hair & skin in vertebrates
  • waterproofing of feathers in birds
  • protection from evaporation in tropical plants and ivy
  • used by people in lotions, ointments, and polishes
55
Q

Triacontanoylpalmitate, major component of beeswax, is ?

A

An ester of palmitic acid with the alcohol triacontanol

56
Q

Waxes form ?

A

Protective coats on leaves / fruits and on birds & mammals. Bees use wax in the construction of their larval chambers

57
Q

Biological waxes e.g. lanolin/beeswax & Carnuba wax (palm) are widely used in?

A

Lotions, ointments & polishes

58
Q

What are sterols ?

A

Structural membrane lipids with 4 fused carbons

59
Q

Cholesterol and related sterols are present in ?

A

The membranes of most eukaryotic cells

  • modulate fluidity and permeability
  • thicken the plasma membrane
  • no sterols in most bacteria
60
Q

Mammals obtain cholesterol from ?

A

Food or synthesise it de novo in the liver

61
Q

Cholesterol, bound to proteins, is transported to ?

A

Tissues via blood vessels

- Cholesterol in low-density lipoproteins tends to deposit and clog arteries

62
Q

Many hormones are derivatives of ?

A

Sterols

63
Q

What cannot synthesise sterols ?

A

Bacteria cannot synthesise sterols

64
Q

Vitamin D is derived from?

A

Vitamin D is derived from cholesterol in a series of reactions, one of which requires UV light to break the bond between two C atoms

65
Q

Steroids are oxidised derivatives of ?

A

Sterols

66
Q

Steroids have the ? but lack?

A

Steroids have the sterol nucleus but lack the alkyl chain found in cholesterol

67
Q

Steroids are more polar than?

A

Cholesterol

68
Q

Steroid hormones are synthesised from ?

A

Cholesterol in gonads and adrenal glands

69
Q

How are they carried through ?

A

They are carried through the body in the bloodstream, usually attached to carrier proteins

70
Q

Many of the steroid hormones are ?

A

Male and female sex hormones

Biological Chemistry (15 decks)

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