Lipids Flashcards
Biological functions of lipids
-Storage of energy - reduced compounds, hydrophobic nature
-Insulation from environment - low thermal conductivity, high heat capacity, mechanical protection
-Water repellent - hydrophobic
-Buoyancy control and acoustics in marine mammals
-Membrane structure
-Cofactors for enzymes - vit K for blood clot formation, coenzyme Q for ATP synthesis
-Signalling molecules
-Pigments
-Antioxidants - vit E
What are carotenoids?
Lipids that can provide colour e.g canthaxanthin (bright red), Zeaxanthin (bright yellow)
What are the 2 types of lipids that contain fatty acids?
Storage lipids (Glycerol and 3 fatty acids)
Mmembrane lipids - more complex
What are the 3 types of membrane lipids and what can these be broken into
- Phospholipids
-Glycerophospholipids (Glycerol, 2 fatty acids, phosphate+alcohol)
-Sphingolipids (Sphingosine, 1 fatty acid, PO4+choline - Glycolipids
-Sphingolipids (Sphingosine, 1 fatty acid, mono or oligosaccharide
-Galactolipids (sulfolipids) (Glycerol, 2 fatty acids, mono or disaccharide+(SO4) - Archael ether lipids (3 glycerols, 2 diphytanyl, 2 PO4)
What are trans fats and give examples
Unsaturated fatty acids that have be modified in food processing and made bad for you
E.g Hydrogenated vegetable oils, fast foods, cakes/pastries, chocolate, deep fried food
What are the 2 types of saturated fatty acids and give examples
-Have no double bonds
i) Vegetable fats - coconut, palm oil, 3 in 1 beverages, creamer, condensed milk
ii) Animal fats - poultry skin, fatty meat, butter, ghee, tallow lard, full cream dairy products
What are unsaturated fatty acids, what are the 2 types and give examples
-Has double bonds and are good for you
i) Polyunsaturated fats - com oil, soybean oil, sunflower oil, seeds, cold water fish
ii) Monounsaturated - olive oil, canola oil, peanut oil, sesame oil, avocado, most nuts
What is a fatty acid made up of?
Carboxylic acids (polar) with hydrocarbon chains (non polar) containing between 4-36 carbons
Almost all FAs have even no. of carbons
Most arev unbranched
Delta numbering VS Omega numbering
Delta - decribes location of first carbon of the alkene (dbl bond) in relationship to the carbonyl carbon (carbon in carboxyl end)
Omega - describes location of first carbon of alkene in relation to terminal methyl (last carbon)
As length of the fatty acid increases the melting point……..
solubility…………
Melting point increases if saturated (no dbl bonds) and decreases if number of double bonds increase as less tightly packed together
Solubility decreases as non polar hydrocarbon end is increasing as the chain is getting longer - hydrophobic effect is increasing
What are the 2 main classes pf polyunsaturated fatty acids (PUFA)?
Omega - 3 and Omega - 6
Humans need them but cant synthesize them
What is the conformation of fatty acids?
-Saturated chain tends to adopt extended conformations
-Double bonds in natural unsaturated fatty acids are mostly in cis configuration which kinks the chain
How do trans fatty acids form and what are their characteristics?
-By partial dehydrogenation of unsaturated fatty acids
-Done to increase shelf life or stability at high temps pf poils used in cooking
-Trans fatty acids can pack more and show higher melting points
What can consuming trans fats increase the risk of?
Cardiovascular disease
What is the principal trans unsaturated fatty acid?
Elaidic acid
Fats VS Oils
fats - solid
oils - liquid
Are triglycerides more or less soluble in water than fatty acids? Why?
Triglycerides are less soluble in water than fatty acids due to esterification of carboxylate group
Advantages of fats over polysaccharides?
-FAs carry more energy per carbon because they are more reduced
-FAs carry less water per gram as they are non polar
What are waxes?
Esters of long-chain saturated and unsaturated fatty acids with long chain alcohols
Solubility and melting points of waxes?
Insoluble and have high melting points
Functions of Waxes?
-Stprage of metabolic fuel in plankton
-protection and pliability for skiin and hair in vertebrates
-waterproofing of feathers in birds
-protection from evaporation in tropical plants and ivy
-used in lotions, ointments, polishes
What are 3 types of membrane lipids?
-glycerophospholipid
-glycolipid
-sterol
How do glycerophospholipids (phosphoglyceride) form?
-2 fatty acids form ester linkages with the first and second hydroxyl group of L-glycerol-3-phosphate (L-hydroxyl group on left, 3- 3C has phosphate)
What is the head group in glcerophospholipids?
The highly polar phosphate group may be further esterified by an alcohol - such substituent groups are called the head groups
What are 2 glycerophospholipids that are found in the membrane?
-Phosphatidylcholine (PC) - major component of eukaryotic cell membranes
-Phosphatidylserine (Pts) - early biomarker of apoptotic cell death
How does phosphatidylserine indicate cell death?
In healthy cells there is no PTS found on outer membrane only inner membrane
Early stage apoptosis - PTS found flipped onto outer membrane
How is a fatty acid joined to a sphingosine?
Via an amide linkage (not an ester linkage)
How is a polar head group connected to a sphingosine and where are glycosphingolipids found?
A polar head group is connected to sphingosine by a glycosidic or phosphodiester linkage
- The sugar-containing glycosphingolipids are found in outer surface of plasma membranes
What is the backbone of a sphingolipid?
A long chain amino alcohol called a sphingosine
Where would you find i) Sphingomyelin ii)Gangliosides
Sphingomyelin - found on myelin sheaths
Gangliosides - within cells of CNS
What are the blood groups determined by?
The type of sugars loacted on the head groups in glycosphingolipids
e.g N-acetylgalactosamine for A blood group
D-galactose for B blood group
What enzyme creates the expression for the structure of sugar on the head groups of glycosphingolipids for blood groups?
Glycosyltransferase
What antigen will individuals with no active glycosyltransferase have?
The O antigen
Where is cholesterol found and what are its functions?
-Found in membranes of most eukaryotics - not in bacteria
-Func: modulate fluidity and permeability, thicken plasma membrane
What is tested for to check cholesterol levels - if too high?
Low- density lipoproteins - tend to deposit and clog arteries
What are phospholipids degarded by?
Phospholipases A-D each cleaves a specfic bond
(Degrade gangliosides)
What can failure to correctly degrade gangliosudes result in?
-Build up of lipids in lysosomes, dysfunction categorized as ‘lysosomal storage disorders’
e.g Batton disease, gauches disease- affect neurological system
What are polyketides?
Biologically active lipids with medicinal uses e.g erythromycin
e.g lovastatin- lower cholesterol
