Week 6 (structure and function of lipids)

Question 1

Describe biological lipids

Answer 1

Chemically diverse
Functionally diverse
Insoluble in water
Fats and oils principle form of stored energy for organisms.

Question 2

What are fatty acids?

Answer 2

Hydrocarbon derivatives

Question 3

Describe the structure of fatty acids

Answer 3

Carboxylic acids
Hydrocarbon chains 4 to 36 carbons long.
Chains can be saturated (no double bonds) or unsaturated (contains double bonds)

Question 4

Name the 2 isomerism structures of fatty acids

Answer 4

Cis
Trans

Question 5

What are the physical properties of fatty acids determined by?

Answer 5

Length
Degree of unsaturation

Question 6

What are the physical properties of fatty acids?

Answer 6

Solubility (the longer the chain and fewer the double bonds the lower the solubility in water)
Melting point (the greater the number of unsaturated/double bonds the lower the melting point. Double bonds result in a kink in the tail which reduces the packing of fatty acids)

Question 7

Describe the structure of triglycerides

Answer 7

3 fatty acids
3 ester bonds (between fatty acids and glycerol molecule)
1 glycerol molecule

Question 8

What do triglycerides do?

Answer 8

Store energy
Provide insulation

Question 9

What are biological waxes?

Answer 9

Esters of long chain fatty acids + long chain alcohols.

Question 10

Describe omega-3 fatty acids

Answer 10

Have an important role in nutrition.
Double bond nearest methyl end is important (label from that end)

Question 11

What do humans require but lack the ability to synthesis?

Answer 11

a-linolenic acid
Therefore it must be obtained from the diet.

Question 12

What can an imbalance of omega 6 and 3 lead to?

Answer 12

An increased risk of CVD

Question 13

What is the optimal ratio of omega 6 to 3?

Answer 13

3:1 to 4:1

Question 14

What is the role of phospholipid bilayer?

Answer 14

Act as a barrier to polar molecules and ions.

Question 15

Describe the structure of the membrane lipids in the phospholipid bilayer

Answer 15

Amphipathic
Packaged into sheets
Hydrophobic interactions between each other.
Hydrophilic head interacts with water.

Question 16

Name the 5 general types of structural lipids

Answer 16

Glycerophospholipids (phospholipids)
Sphingolipids (phospholipid/glycolipid)
Galactolipids/sulfoxides (glycolipids)
Archaeal ether lipids
Sterols

Question 17

Describe glycerophospholipids

Answer 17

Two fatty acids, glycerol and phosphodiester.
Named phosphatidyl-x (where x is the polar alcohol head): phosphatidylcholine.
Polar heads can be charged or neutral; contribute to surface properties of membranes.

Question 18

What are galactolipids?

Answer 18

Predominate in plant cells.
Located in the internal membranes of chloroplasts.
70-80% of membrane lipids of vascular plants.
Most abundant membrane lipid in biosphere.

Question 19

Describe sphingolipids

Answer 19

Contains polar head and two non-polar tails, but no glycerol.
Contains sphingosine (long-chain amino alcohol).
Three subclasses.
60+ different sphingolipids.
Prominent in plasma membrane of neurons.
Recognition sites on cell surface.
Play an important role in the determination of blood groups.

Question 20

Name the 3 subclasses of sphingolipids

Answer 20

Sphingomyelins
Glycolipids
Gangliosides

Question 21

Describe sphingomyelins

Answer 21

Polar head = phosphocholine or phosphoethanolamine.
Classified as a phospholipid.
Found in plasma membrane of animal cells.
Prominent in myelin (neurons): insulate axons.

Question 22

Describe glycosphingolipids

Answer 22

Polar head = one or more sugars
Cerebrosides = one sugar.
Galactose = plasma membrane of neuronal tissue.
Glucose = plasma membrane of non-neuronal tissue.

Question 23

Describe gangliosides

Answer 23

Most complex polar head = oligosaccharides.
At termini: one or two sialic acid residues (negative charge)

Question 24

Describe sterols

Answer 24

Structural lipids in most eukaryotic cells.
Animal tissue = cholesterol

Question 25

Describe cholesterol

Answer 25

Key component of cell membrane
- maintains integrity
- maintains fluidity
- anchors proteins (lipid rafts)
Precursors
- steroids hormones
- bile acids
Separates the phospholipids so that the fatty acid tails don’t crystallise with one another.

Question 26

What are metabolites and messengers?

Answer 26

A family of lipids that have active roles.

Question 27

Give examples of metabolites and messengers

Answer 27

Hormones
Enzyme cofactors
Pigment molecules

Question 28

Describe phosphatidylinositol (PIP2)

Answer 28

Located in the cytoplasmic force of plasma membrane.
Reservoir of messenger molecules: formation of inositol and important in muscle contraction.

Question 29

What are eicosanoids?

Answer 29

Paracrine hormones
All derived from arachidonic acid.

Question 30

What are the roles of eicosanoids?

Answer 30

Roles in reproduction, inflammation, fever, pain, formation of blood clots, blood pressure regulation, gastric acid secretion.

Question 31

Name the 3 classes of eicosanoids

Answer 31

Prostaglandins (PG)
Thromboxane
Leukotrienes

Question 32

What are the roles of prostaglandins?

Answer 32

Elevate temperature (fever)
Affects blood flow
Contraction of smooth muscle in menstruation and labour.

Question 33

What are the roles of thromboxanes?

Answer 33

Produced by platelets.
Role in formation of blood clots.
Reduce local blood flow.

Question 34

What are steroid hormones?

Answer 34

Oxidised derivatives of sterols.
Move through the bloodstream bound to plasma proteins.
4 carbon ring.
Oxidised derivatives of cholesterol.
Lipophilic.

Question 35

What is vitamin D?

Answer 35

Considered a hormone.
Uses cholesterol as its base unit.
Can be stored for up to 3 months in the liver and then is metabolised to be circulated in its more active form,
Travels through the blood, bound to plasma proteins.

Question 36

What is vitamin A?

Answer 36

A lipid vitamin