Lipids Flashcards
Lipids are
A diverse group of compounds that are insoluble in water but soluble in organic solvents such as ethanol
The most common type is triglycerides
Difference between lipids and carbohydrates structure wise
Lipids contain a higher proportion of hydrogen and a lower proportion of oxygen
Triglyceride structure
Glycerol backbone joined to three fatty acid chains by an Ester bonds
Formed from a condensation reaction
Why are fatty acids insoluble/hydrophobic
Because they’re very bing and very long
Saturated fatty acids
Fatty acid in which all carbon atoms have four bonds
Unsaturated fatty acids
Some of the carbon atoms have a double bond joining them to a neighbouring atom and creating a kink in the chain
Unsaturated triglyceride
A triglyceride contains one fatty acid
Mostly made by plants
Polysaturated triglyceride
Triglyceride containing two or three fatty acids
Mostly made by animals
Role of lipids
Energy source
Stored in adipose tissue for
Heat insulation (adipose tissue underneath skin preventing heat loss)
Protection (around delicate organs such as kidneys to act as a cushion against impacts)
Phospholipids
The third fatty acid is replaced by a phosphate group Insoluble Hydrophilic head Hydrophobic tail Major component of cell membranes
Fatty acids and cis and trans configurations
Type of fatty acid determines triglycerides properties such as melting point
Cis configuration makes the greatest kink in fatty acids making them not closely packed together and have weaker bonds making them liquid at room temperature eg oil
Trans configuration has stronger bonds
Test for lipid
Emulsion test
Shake sample with ethanol in test tube
If lipids present some will dissolve
Gently pour ethanol into another test tube containing water
If lipids are present droplets are formed which makes the water cloudy
