Fatty Acids & Lipids Flashcards
2 characteristics of lipids
- Low solubility in water
- Relatively hydrophobic
9 function of lipids
- Energy storage: good packing due to hydrophobic nature
- Insulation from Environment: high heat capacity (can “absorb” heat)
- Water repellant: hydrophobic nature
- Bouyancy control & acoustics in in marine mammals
- Membrane structure: main structure of cell membranes
- Cofactors for enzymes: vit K - blood clot formation
- Signaling molecules: growth factors, hormones
- Pigments: colour of tomatoes, carrots
- Antioxidants: Vit E
Two major lipid categories
- Lipids that contain fatty acids (complex lipids)
- Lipids that dont contain FAs (cholesterol, vitamins, pigments)
What categories can complex lipids be further divided into
- Storage lipids
- Membrane lipids
What is the healthy kind of fat
Unsaturated fat - contains double bonds
Which 2 fats are the unhealthy fats
- Trans fats
- Saturated fats
Saturated fats
No double bonds between carbons in the alkyl chain
Monounsaturated fats
One double bond between carbons in the alkyl chain
Polyunsaturated fats
More than one double bond in the alkyl chain
What would 18:1 delta 9 mean
- 18 carbons
- 1 double bond
- Double bond on 9th carbon from carbonyl carbon (COOH carbon)
What does 18:1 omega 9 mean
- 18 carbons
- 1 double bond
- Double bond 9 carbons from the terminal methyl (last carbon)
What happens when the length of hydrocarbon chain increases in FAs (2)
- The solubility of the FA in water decreases, as molecule is becoming more non polar, less able to form hydrogen bonds with water
- The melting point of the FA increases also
What are the 2 major classes of polyunsaturated FAs
- Omega 6
- Omega 3
(essential FAs)
What does the cis configuration of double bonds do to the fatty acid chain
Kinks the chain
What way do saturated FAs pack
In an orderly way - no d bonds = no kinks in chains
What way do unsaturated FAs pack
Less orderly due to the kink (caused by double bond)
Do unsaturated or saturated cis FAs have a lower melting point & why
Unsaturates cis FAs have a lower melting point as they are packed less tightly so require less energy to break, therefore they have a lower melting point
By what process do trans fatty acids form
By partial dehydrogenation of unsaturated FAs
Melting point of trans unsaturated FAs
A trans double bond does not form a kink.
Trans FAs can pack more tightly and therefore have higher melting points.
What is a triglyceride
A lipid with 3 FAs esterified by a glycerol backbone
Solubility of triglycerides in water compared to that of FAs
Less soluble in water than FAs due to esterification of carboxylate group
What are waxes
Esters of long chain saturated & unsaturated FAs with long chain alcohols
Solubility & melting point of waxes
- Insoluble
- High mp
5 functions of waxes
- Storage of metabolic fuel in plankton
- Protection & pliability for hair & skin
- Waterproofing of feathers
- Prtection from evaporation in tropical plants
- Used in lotions, ointments, polishes
3 types of membrane lipid
- Glycerophospolipid
- Glycerolipid
- Sterol - contains steroid rings
Structure of glycerophospholipids
Two FAs form ester linkages with the 1st & 2nd hydroxyl groups of L-glycerol-3-phosphate
* Head group substituent
* Glycerol
* Fatty acids
What is the backbone of sphingolipids
The backbone of sphingolipids is long chain amino alcohol sphingosine
In sphingolipids, the FA is joined to sphingosine via what kind of linkage
Amide linkage
What are glycosphingolipids
A subgroup of sphingolipids that contain saccharide head groups
Structure of sterols
- Four fused rings of steroid nucleus gives rigidity
- Hydroxyl group (polar head) in A-ring
- Non polar side chains
Physiological role of sterols
- Cholesterol & related sterols in membranes of eukaryotic cells
- Modulate fluidity & permeability
- Thicken plasma membrane
What are phospholipids degraded by
Phospholipases A-D
Each cleaves a specific bond
Where are structural & signalling lipids degraded
In the lysosome
Examples of polyketides (biologically active lipids with medicinal uses)
- Erythromycin (antibiotic)
- Amphotericin B (anti fungal)
- Lovastatin (statin) - cholesterol lowering drugs