Lipid Properties

Question 1

Lipids

Answer 1

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

Question 2

Structurually, what are fatty acids?

Answer 2

Carboxylic acids with long hydrocarbon side chains

Question 3

What form are fatty acids mostly in?

Answer 3

Esterfied form.

Question 4

Esterfied

Answer 4

A compound produced by combination of alcohol and acid.

Question 5

How many carbons do FA most commonly have?

Answer 5

Between C16 and C18 carbons.

Question 6

What are the most common fatty acids?

Answer 6

Palmitic, Oleic, Linoleic and Stearic acids.

Question 7

Why are most fatty acids an even number of carbons?

Answer 7

Their synthesis happens in C2 units.

Question 8

Unsaturated fatty acids

Answer 8

FA with double bonds, being either mono or poly.

Question 9

Where do UFA double bonds occur most?

Answer 9

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

Question 10

How are PU fats identified in nomenclature?

Answer 10

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

Question 11

An example of PU nomenclature

Answer 11

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

Question 12

Why are unsaturated fats useful in membrane fluidity?

Answer 12

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

Question 13

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

Answer 13

Due to reduced VDW forces.

Question 14

Saturated Fatty Acids

Answer 14

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

Question 15

Why are fatty acid linear forms more favourable?

Answer 15

Have the least amount of steric interference between methyl groups.

Question 16

Triacylglycerols

Answer 16

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

Question 17

Function of triglycerides

Answer 17

Energy reservoirs in animals

Question 18

How are triacylglycerols named?

Answer 18

According to the placement of their glycerol moiety.

Question 19

An example of triglyceride nomenclature?

Answer 19

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

Question 20

Why are fats more efficent as metabolic energy stores?

Answer 20

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

Question 21

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

Answer 21

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

Question 22

How are adipocytes specialised for synthesis/storage of TAG?

Answer 22

Adipocytes are almost entirely filled with fat globules.

Question 23

What is the importance of adipocyte fat storage?

Answer 23

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

Question 24

What is the most abundant membrane lipid?

Answer 24

Glycerophospholipids

Question 25

What is the structure of glycerophospholipids?

Answer 25

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

Question 26

What is the saturation properties of glycerophospholipids?

Answer 26

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

Question 27

What catalyses glycerophospholipid hydrolysis?

Answer 27

Phospholipases.

Question 28

What is an example of glycerophospholipid hydrolysis?

Answer 28

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

Question 29

Sphingolipids

Answer 29

A lipid class contaiing the sphingosine.

Question 30

Sphingosine

Answer 30

An amino alchol with an 18-carbon unsaturated alkyl chain

Question 31

Ceramides

Answer 31

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

Question 32

What is the most common ceramide?

Answer 32

Sphingomyelin, ceramides bearing a phosphocholine or phosphoethanolamine head group.

Question 33

How much of plasma membrane lipids are sphingomyelins?

Answer 33

10 to 20%

Question 34

Cerebrosides

Answer 34

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

Question 35

Gangliosides

Answer 35

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

Question 36

Why are gangliosides important in medical and physiological areas?

Answer 36

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

Question 37

Isoprenoids

Answer 37

Lipids used in pigmentation, fragrances and vitamins.

Question 38

What is an example of an Isoprenoid?

Answer 38

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

Question 39

Vitamin A

Answer 39

A fat-soluble vitamin deriving from carotene

Question 40

How does Vitamin A relate to eyesight?

Answer 40

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.

Question 41

Vitamin K

Answer 41

A lipod important in blood clotting and bone formation

Question 42

How does Vitamin K relate to blood clotting?

Answer 42

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

Question 43

Vitamin E

Answer 43

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

Question 44

Elicosanoids

Answer 44

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

Question 45

What is the major lung surfactant lipid?

Answer 45

Dipalmitoyl Phosphatidylcholine, coating alveoli, decreasing surface tension.

Question 46

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

Answer 46

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

Question 47

Function of DPPC in surfactant?

Answer 47

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