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Biology - Macromolecules > Lipid Properties > Flashcards

Lipid Properties Flashcards

1
Q

Lipids

A

Organic substances soluble in organic solvents, making them easily seperated from organic material.

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2
Q

Structurually, what are fatty acids?

A

Carboxylic acids with long hydrocarbon side chains

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3
Q

What form are fatty acids mostly in?

A

Esterfied form.

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4
Q

Esterfied

A

A compound produced by combination of alcohol and acid.

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5
Q

How many carbons do FA most commonly have?

A

Between C16 and C18 carbons.

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6
Q

What are the most common fatty acids?

A

Palmitic, Oleic, Linoleic and Stearic acids.

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7
Q

Why are most fatty acids an even number of carbons?

A

Their synthesis happens in C2 units.

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8
Q

Unsaturated fatty acids

A

FA with double bonds, being either mono or poly.

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9
Q

Where do UFA double bonds occur most?

A

Between C9 and C10, and typically every third carbon in polyunsaturated fats.

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10
Q

How are PU fats identified in nomenclature?

A

Omega 3 and Omega 6 FA, identifying the last double-bonded carbon atom as counted from the methyl terminated end of the chain.

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11
Q

An example of PU nomenclature

A

Linolenic acid has double bonds between C9-10 and C12-C13, whilst a-linolenic acid between C9-C10, C12-13 and C15-C16

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12
Q

Why are unsaturated fats useful in membrane fluidity?

A

They are almost always in cis configuration, allowing a 30 degree bend in the chain, packing less efficinetly together.

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13
Q

Why do Unsaturated FA melting points decrease with degree of unsaturation?

A

Due to reduced VDW forces.

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14
Q

Saturated Fatty Acids

A

FA fully saturated with H, being highly flexible, allowing wide range of conformations due to free range of each bond

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15
Q

Why are fatty acid linear forms more favourable?

A

Have the least amount of steric interference between methyl groups.

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16
Q

Triacylglycerols

A

Non-polar, water insoluble substances of FA bound to a glycerol backbone.

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17
Q

Function of triglycerides

A

Energy reservoirs in animals

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18
Q

How are triacylglycerols named?

A

According to the placement of their glycerol moiety.

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19
Q

An example of triglyceride nomenclature?

A

1-palmitoleoyl-2-linoleoyl-3-stearoylglycerol, where palmitoleoyl is found on C1 of glycerol, linoleoyl on C2 and stearoylglycerol on C3

20
Q

Why are fats more efficent as metabolic energy stores?

A

They are less oxidised than carbohydrates and proteins, yielding far more energy per unit mass on complete oxidation

21
Q

How, based on how they’re stored, are fats more efficent than glycogen?

A

Fats are stored in anhydrous form, whilst glycogen holds twice its weight in water.

22
Q

How are adipocytes specialised for synthesis/storage of TAG?

A

Adipocytes are almost entirely filled with fat globules.

23
Q

What is the importance of adipocyte fat storage?

A

Allow survival from starvation for up to 2 to 3 months, whilst supplying thermal insulation.

24
Q

What is the most abundant membrane lipid?

A

Glycerophospholipids

25
Q

What is the structure of glycerophospholipids?

A

A glycerol-3-phosphate backone, linked to a polar group, with C1 and C2 positions esterfied with fatty acids.

26
Q

What is the saturation properties of glycerophospholipids?

A

They contain a saturated C16/18 at C1 with C2 occupied by unsaturated C16-20 FA.

27
Q

What catalyses glycerophospholipid hydrolysis?

A

Phospholipases.

28
Q

What is an example of glycerophospholipid hydrolysis?

A

Phospholipase A2 hydrolytically excises C2 fatty acid residue producing lysophospholipids, with disrupt lysis.

29
Q

Sphingolipids

A

A lipid class contaiing the sphingosine.

30
Q

Sphingosine

A

An amino alchol with an 18-carbon unsaturated alkyl chain

31
Q

Ceramides

A

N-acyl fatty acid derivatives of sphingosines, parent compounds of sphingolipids.

32
Q

What is the most common ceramide?

A

Sphingomyelin, ceramides bearing a phosphocholine or phosphoethanolamine head group.

33
Q

How much of plasma membrane lipids are sphingomyelins?

A

10 to 20%

34
Q

Cerebrosides

A

Ceramides with head groups of a single sugar residue, lacking phosphate groups being non-ionic

35
Q

Gangliosides

A

Fats with ceramides attaching to oligosaccharides, including at least one sialic acid residue.

36
Q

Why are gangliosides important in medical and physiological areas?

A

Due to their carbohydrate head groups which extend beyond the surfaces of cell membranes, acting as receptors for pituitary hormones that regulate physiological functions.

37
Q

Isoprenoids

A

Lipids used in pigmentation, fragrances and vitamins.

38
Q

What is an example of an Isoprenoid?

A

Isoprenoid ubiquinone, (coenzyme Q), which is reversible reduced and oxidised in the mitochondrial membrane.

39
Q

Vitamin A

A

A fat-soluble vitamin deriving from carotene

40
Q

How does Vitamin A relate to eyesight?

A

Retinol is oxidised to aldehyde form retinal, functioning as the eyes photoreceptor at low light intesities, causing retinal isomerization, triggering signalling pathways in optic nerves.

41
Q

Vitamin K

A

A lipod important in blood clotting and bone formation

42
Q

How does Vitamin K relate to blood clotting?

A

In carboxylates glu residues in blood clotting proteins, so deficiency has reduced carboxylation, resulting in inactive clotting proteins and excess bleeding.

43
Q

Vitamin E

A

A highly hydrophobic molecule, incorporating into cell membranes functioning as an antioxidant to prevent oxidative damage to membrane proteins and lipids.

44
Q

Elicosanoids

A

A non-membranous lipid active in production of pain and fever and regulating blood pressure, coagulation and reproduction.

45
Q

What is the major lung surfactant lipid?

A

Dipalmitoyl Phosphatidylcholine, coating alveoli, decreasing surface tension.

46
Q

How does the structure of DPPC allow them to pack closely?

A

They are sturated, thus extend straight out without bending and orientation in a signle layer with non-polar tails toward air.

47
Q

Function of DPPC in surfactant?

A

In expiration, volume/SA of alveoli decreasing with full colappse prevented by DPPC.

Biology - Macromolecules (16 decks)

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