Week 6 Structural Lipids

Question 1

Structural lipids

Answer 1

Key architectural feature of biological membranes - phospholipid bilayer
—Acts as a barrier to polar molecules & ions
—Membrane lipids are amphipathic
—Packaged into sheets
— Hydrophobic interactions between each other
— Hydrophilic head interacts with water

Question 2

Five general types of structural lipids:

Answer 2

Glycerophospholipids (phospholipid) -contain only phospholipids
— Sphingolipids (phospholipid/glycolipid)
— Galactolipids/sulfolipids (glycolipid)
—Archaeal ether lipids
— Sterols ridged ring of 5 carbon very strong

Question 3

Glycerophospholipids

Answer 3

Two fatty acids, glycerol and phosphodiester

Named phosphatidyl-x
—Phosphatidylcholine
(where x is the polar alcohol head)

—Polar heads can be charged (neg/pos) or neutral(quite unusual)
— Contributes to surface properties of membranes

Question 4

Galactolipids

Answer 4

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?
2 fatty acid chains conecte to a glycerol
Carbohydrate residue

Question 5

Sphingolipids

Answer 5

Contains polar head and two non-polar tails, but no glycerol
—Contains sphingosine (long-chain amino alcohol)
— Three subclasses
— Sphingomyelins
— Glycolipids
— Gangliosides

Question 6

Sphingomyelins

Answer 6

Polar head = phosphocholine or phosphoethanolamine
—Classified as a phospholipid
— Found in plasma membrane of animal cells
— Prominent in myelin (neurons). Insulating axon

Question 7

Glycosphingolipids

Answer 7

Polar head = one or more sugars
Cerebrosides = one sugar
Galactose – plasma membrane of neuronal tissue
Glucose – plasma membrane of non-neuronal tissue
^Distinguish where the found

Question 8

Gangliosides

Answer 8

Most complex, polar head = oligosaccharides
At termini – one or two sialic acid residues (neg charge)

Question 9

Sphingolipids

Answer 9

60+ different sphingolipids identified in humans
Prominent in plasma membrane of neurons

Recognition sites on cell surface
Some carbohydrate moieties define human blood groups

Phospholipases/lysophospholipases - hydrolytic enzymes

Question 10

Sterols

Answer 10

Structural lipids in most eukaryotic cells
Animal tissue – cholesterol

Non polar tail
Polar head group
Ring steroid ring structure

Question 11

Cholesterol

Answer 11

Key component of cell membrane
-Maintains integrity
- Maintains fluidity
- Anchors proteins (lipid raft)
Head Closely attracted to the phospholipid head
Immobilise the outer membrane
Extra water tight to cell membrane preventing very small molecules to pass through

Separate phospholipids so. They can’t crystallise

• Precursor for
• Steroids hormones
  -Bile acids