Lipids Flashcards
Name two groups of lipids
Triglycerides and phospholipids
How are triglycerides formed?
Condensation reaction of 1 molecules of glycerol and 3 molecules of fatty acid
OH of the glycerol joins with the H of the fatty acid
What is the bond formed between the glycerol and fatty acid ?
Ester bond
The R-group of a fatty acid can be …
saturated or unsaturated
Describe the structure of a phospholipid
one fatty acid of a triglyceride is substituted by a phosphate-containing group
Name the test for lipids
emulsion test
Describe the emulsion test
Put 2cm2 food sample into a grease free test tube
Add 5cm3 of ethanol } shake
Add 5cm3 of water } shake
Describe the results of the emulsion test if lipids are present
White mixture as precipitate has formed
Describe the 5 properties of triglycerides which makes them useful
[insoluble in water /soluble in organic solvents]
Source of energy= releases valuable water and 2x energy as the same mass of carbohydrates
Waterproofing: waxy lipid cuticle/sebaceous gland
Thermal insulation= slow conductor of heat
insulation = electric insulator in myelin sheath around nerve cells
Protection = Around delicate organs or plasma membrane
Describe the difference between fats and oils
fats are solid at rt
oils are liquid at rt
Name the properties of triglycerides
Good source of energy = High energy storing C-H bond:
low mass to energy ratio = reduces mass needed to carry around
insoluble bc of size = not affected by osmosis or water potential
high ratio of H to O atoms= provide important source of water
Define saturated
no carbon-carbon double bonds
fully saturated with hydrogen atoms
Define unsaturated
monounsaturated polyunsaturated
having carbon–carbon double or triple bonds not containing the greatest possible number of hydrogen atoms.
What is a amphipathic molecule?
hydrophilic head and hydrophobic tail
Describe the main property of phospholipids
Phosphate head = hydrophilic fatty acid = hydrophobic
forms a bilayer
