Wee 6 Structure And Function Of Lipids Flashcards
Lipids
Biological lipids
-Chemically diverse
-Functionally diverse
- Defining feature – insolubility in water
Storage lipids
Fats & oils principle form of stored energy for organisms -Are derivatives of fatty acids
- Fatty acids – hydrocarbon derivatives
-Triglycerides & waxes contain fatty acids
Highly exogonic
Fatty acids
Carboxylic acids
Hydrocarbon chains 4 to 36 carbons long (C4 to C36)
Chains can be saturated (no double bonds) or unsaturated (contains double bonds)
Fatty acid nomenclature
Palmitic acid is abbreviated as 16:0
First carbon attached to carboxiliac end
Oleic acid is abbreviated as 18:1D9
Denotes position of double bond
Double bond Found at postion 9
Isomerism
Trans c are opposite sides of the double bind
Polyunsaturated fatty acids (PUFAs)
Omega-3 (ω-3) fatty acids important role in nutrition
- Termed so due to position of double bond
- Double bond nearest methyl end is important so can label from that end
- Omega-6 fatty acids – double bond between carbon 6 & 7 From methyl end
(Opposite from carboxylic end )
Omega-3 fatty acids
umans require but lack ability to synthesise α-linolenic acid (ALA; 18:3D9,12,15)
Must obtain from diet
-From ALA can synthesise
— Eicosapentaenoic acid (EPA; 20:5D5,8,11,14,17)
— Docosahexaenoic acid (DHA; 22:6D4,7,10,13,16,19)
Chia, walnuts, kiwi seeds
Imbalance of omega-6 & -3 can = risk of CVD
- Optimal ratio omega-6 to -3, 1:1 to 4:1 Ratio in N.
—American diets, 10:1 to 30:1
—‘Mediterranean diet’ rich in omega-3
Fatty acids
Physical properties
—Determined by length & degree of unsaturation
— Solubility – longer the chain & fewer the double bonds = lower solubility in water
Melting point – greater number of unsaturated/double bonds
—Lower melting point
— Double bonds = ‘kink’ in tail = reduced packing of fatty acids
Glucose Oxygen is electronegative = pull electrons towards it leaving hydrogen electro postive = solubility in h20 is higher
Saturated fatty acids = lots together, van de waals bonds
Unsaturated fatty acids kinks = unable to line up, Limited van de waals bonds, less heat to melt it
Triglycerides
Also known as triacylglycerols, fats or neutral fats
—Triglyceride structure = 3 fatty acids, 3 ester bonds, 1 glycerol
Non polar = hydrophobic, insoluble in water
Triglycerides provide stored energy & insulation
—Form separate phase in aqueous cytosol – droplets of metabolic fuel
— Adipocytes store fat droplets (nuclei pushed out to edge of plasma membrane)(not many mitochondria)
Energy from fats
Fats = 9 cal per gram, not many o2, highly reduced, don’t carry water as there insoluble
Protien = 4 cal per gram
Carbs = 4 cal per gram
Storage from fats
White adipose under are skin
Acts as insulation
Partial Hydrogenation of cooking oils
Hydrogenation of oleic acid
Wax
Biological waxes – esters of long chain fatty acids (c14 – C36) + long chain alcohols (c16 – C30)
Insoluble due to the lack of oxygen