Lipids Flashcards
What are 5 biological functions of lipids?
Storage of energy, membrane structure, signaling molecules, cofactors for enzymes, and antioxidants.
Fatty acids with C10 or higher saturated hydrocarbon chains form…
Waxy solids at room temperature.
Fatty acids with C9 or lower saturated or unsaturated hydrocarbon chains are…
Oily liquids at room temperature.
The pKa of the COOH group is…
Less than 5
At what pH are fatty acids fully ionized?
pH 7
Most natural fatty acids…
Have an even number of carbons and are unbranched.
Cis-double bonds affect…
The position o fatty acid tails, results in kinks or bends which equals less ordered packing.
Unsaturated fatty-acids melting points are…
Lower
Solubility and melting point of fatty acids are determined by…
Length of hydrocarbon chains and degree of saturation.
All naturally occurring double bonds have…
Cis configuration.
How do trans fatty acids form?
By partial hydrogenation of unsaturated fatty acids and cis-double bond isomerization to trans double bonds.
When all fatty acids in a triglycerol are the same…
Simple tracylglycerides
When the fatty acids in a triglycerol are different…
Complex triacylglycerides
Triacylglycerols/Triglycerides
Glycerol + 3 fatty acids.
Storage lipid, neutral.
Waxes
Storage lipid, non polar, do not contain glycerol.
How are waxes formed?
By a condensation reaction between long fatty acids and alcohol hydrocarbon chains.
Composition of glycerophospholipid
2 fatty acids and glycerol 3-phosphate backbone.
What type of bond is formed between the phosphate group of glycerophospholipids and the carbon backbone chain?
Phosphodiester bond.
What type of bond connects fatty acids and a carbon backbone (except in sphingolipids)?
Ester bonds.
How are glycerophospholipids formed?
Condensation reaction between two fatty acids and the chiral carbon of glycerol 3-phosphate.
Fatty acids linked to first hydroxyl in glycerophospholipids are generally…
Saturated.
Fatty acids linked to second hydroxyl in glycerophospholipids are generally…
Unsaturated.
Head group
Alcohol based compounds linked to phosphatidic acids.
Sphingolipids are which type of lipid?
Structural, polar.
Sphingolipids structure
Sphingosine backbone (long chain amino alcohol), a fatty acid at C2, and a polar head group.
How is a fatty acid attached to the backbone of a sphingolipid?
Amide linkage.
How are polar head groups connected to the sphingosine backbone of sphingolipids?
Phospho-ester linkage
Sphingomeylin is classified as…
A phospholipid
Glycosphingolipids determine…
Blood groups
Gangliosides
Third group bonded to sphingosine chain in sphingolipids is a sugar.
Phospholipases
Lipid specific enzymes that cleave ester linkages but not ethyl linkages.
Biologically active lipids do not contain…
Fatty acids or glycerol backbone.
Two major classes of biologically active lipids
Prostaglandins and steroids.
How are prostaglandins generated?
Through modification of fatty acids.
How are steroids generated?
From two carbon acids and modification of other sterols.
What is cholesterol made up of?
Steroid nucleus, OH group and non polar branched side chain. Steroid nucleus is almost planar.
Cholesterol prevents…
Close packing of lower ends of fatty acid tails. Decreases melting temp.
Cholesterol promotes…
Tight packing of the upper ends of fatty acid tails. Increases melting temp.
Cholesterol is known as…
The membrane fluidity buffer.
3 structures of lipid aggregates
Lipid micelles, lipid bilayer and liposomes.
Which lipids favour the lipid bilayer aggregate?
Phosphoacylglycerides and sphingolipids.
What is the cell membrane impermeable to?
Charged ions, large molecules or proteins.
What is the cell membrane permeable to?
Hydrophobic molecules and neutral gases and water.
What can lipids do across the bilayer?
Diffuse laterally and spin on axis, but no uncatalyzed flip-flop motion allowed.
What is main asymmetry?
Glycerophospholipids are oriented to the cytoplasm face.
Flippase
Moves things from out to in.
Floppase
Moves things from in the out.
Scramblase
Moves lipids in either direction, towards equilibrium
3 classes of membrane proteins
Integral/intrinsic membrane proteins, anchored membrane proteins and peripheral/associated membrane proteins.
How are integral/intrinsic membrane proteins extracted?
With detergents.
How are anchored membrane proteins extracted?
With detergent or phospholipases.
How are peripheral/associated membrane proteins extracted?
With high pH buffers, denaturing agents and chelating agents.
