Week 6 (structure and function of lipids) Flashcards
Describe biological lipids
Chemically diverse
Functionally diverse
Insoluble in water
Fats and oils principle form of stored energy for organisms.
What are fatty acids?
Hydrocarbon derivatives
Describe the structure of fatty acids
Carboxylic acids
Hydrocarbon chains 4 to 36 carbons long.
Chains can be saturated (no double bonds) or unsaturated (contains double bonds)
Name the 2 isomerism structures of fatty acids
Cis
Trans
What are the physical properties of fatty acids determined by?
Length
Degree of unsaturation
What are the physical properties of fatty acids?
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)
Describe the structure of triglycerides
3 fatty acids
3 ester bonds (between fatty acids and glycerol molecule)
1 glycerol molecule
What do triglycerides do?
Store energy
Provide insulation
What are biological waxes?
Esters of long chain fatty acids + long chain alcohols.
Describe omega-3 fatty acids
Have an important role in nutrition.
Double bond nearest methyl end is important (label from that end)
What do humans require but lack the ability to synthesis?
a-linolenic acid
Therefore it must be obtained from the diet.
What can an imbalance of omega 6 and 3 lead to?
An increased risk of CVD
What is the optimal ratio of omega 6 to 3?
3:1 to 4:1
What is the role of phospholipid bilayer?
Act as a barrier to polar molecules and ions.
Describe the structure of the membrane lipids in the phospholipid bilayer
Amphipathic
Packaged into sheets
Hydrophobic interactions between each other.
Hydrophilic head interacts with water.
Name the 5 general types of structural lipids
Glycerophospholipids (phospholipids)
Sphingolipids (phospholipid/glycolipid)
Galactolipids/sulfoxides (glycolipids)
Archaeal ether lipids
Sterols
Describe glycerophospholipids
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.
What are galactolipids?
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.
Describe sphingolipids
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.
Name the 3 subclasses of sphingolipids
Sphingomyelins
Glycolipids
Gangliosides
Describe sphingomyelins
Polar head = phosphocholine or phosphoethanolamine.
Classified as a phospholipid.
Found in plasma membrane of animal cells.
Prominent in myelin (neurons): insulate axons.
Describe glycosphingolipids
Polar head = one or more sugars
Cerebrosides = one sugar.
Galactose = plasma membrane of neuronal tissue.
Glucose = plasma membrane of non-neuronal tissue.
Describe gangliosides
Most complex polar head = oligosaccharides.
At termini: one or two sialic acid residues (negative charge)
Describe sterols
Structural lipids in most eukaryotic cells.
Animal tissue = cholesterol
Describe cholesterol
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.
What are metabolites and messengers?
A family of lipids that have active roles.
Give examples of metabolites and messengers
Hormones
Enzyme cofactors
Pigment molecules
Describe phosphatidylinositol (PIP2)
Located in the cytoplasmic force of plasma membrane.
Reservoir of messenger molecules: formation of inositol and important in muscle contraction.
What are eicosanoids?
Paracrine hormones
All derived from arachidonic acid.
What are the roles of eicosanoids?
Roles in reproduction, inflammation, fever, pain, formation of blood clots, blood pressure regulation, gastric acid secretion.
Name the 3 classes of eicosanoids
Prostaglandins (PG)
Thromboxane
Leukotrienes
What are the roles of prostaglandins?
Elevate temperature (fever)
Affects blood flow
Contraction of smooth muscle in menstruation and labour.
What are the roles of thromboxanes?
Produced by platelets.
Role in formation of blood clots.
Reduce local blood flow.
What are steroid hormones?
Oxidised derivatives of sterols.
Move through the bloodstream bound to plasma proteins.
4 carbon ring.
Oxidised derivatives of cholesterol.
Lipophilic.
What is vitamin D?
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.
What is vitamin A?
A lipid vitamin
