Lipids

Triglycerides

condensation of one molecule of glycerol and three molecules of fatty acid

condensation reaction between glycerol + fatty acid (RCOOH) →

ester bond

fatty acids R-group =

saturated or unsaturated

saturated lipids

X contain carbon-carbon double bonds

-animal fats

unsaturated lipids

contain carbon-carbon double bonds

-molecule able to bend

-cannot pack together as tightly → liquid at room temperature

-plants

Triglycerides: high ratio of energy storing carbon-hydrogen bonds to carbon atoms

excellent energy store

Triglycerides: low mass to energy ratio

good storage molecule (lot of energy stored in small volume)

-less mass to move around

Triglycerides: large & non-polar lipids

insoluble in water

-storage X affect water potential within cells

Triglycerides: high ratio of hydrogen-oxygen atoms

release water when oxidised

-provide source of water in dry environments

Phospholipids

one molecule of glycerol

two fatty acids

phosphate group

phosphate head →

hydrophilic

phosphate tail →

hydrophobic

phospholipids + water =

formation of micelles = molecule is polar

Phospholipids - polarity

in aq. environment = bilayer forms

Phospholipids - hydrophilic heads

hold at surface of cell surface membrane

phospholipids - form glycolipids

due to surface, important on cell surface membrane for cell recognition

emulsion test

1. add 2cm³ of sample to be tested w/ 5cm³ ethanol

2. shake test tube thoroughly to dissolve all lipid

3. add 5cm³ and shake gently

4. cloudy white emulsion

5. repeat experiment w/ water as sample (control) → remain clear

lipids soluble in =

organic solvents (alcohols)