LipidsLearning objectives…

• Show the formation of a triglyceride•Compare the structure of phospholipids and triglycerides

• Relate structure to function

Type of lipids…

• Triglycerides

• Phospholipids

Glycerol + 3 fatty acids triglyceride+ waterCONDENSATION

Triglyceride + water glycerol + 3 fatty acids HYDROLYSIS

Glycerol and Fatty Acids• Found in all storage fats and oils, including membranes• The glycerol molecule is always the same, but the fatty

acid differs• Most fatty acids can be made, except for ones called

essential fatty acids which must be eaten

Fatty Acids• All fatty acids have an acid group (part) at one

end, the rest of the molecule is a hydrocarbon chain (a chain made of carbons and hydrogens)

• The hydrocarbon chain can be 2 to 20 carbons long, but most have around 18

Acid Group Hydrocarbon chain

Phospholipids• Almost the same as a triglyceride, but the third fatty acid is

not added, instead a phosphate joins to the 3rd OH by a condensation reaction

• The phosphate head is hydrophilic, and the fatty acids are hydrophobic.

• As the majority of the molecule is insoluble, but the phosphate head is hydrophilic it is able to form membranes

Phospholipids in membranes• Phospholipids may still be

saturated or unsaturated.• Organisms can control the

fluidity of their membranes using this feature

• Organisms living in colder climates have more unsaturated fatty acids in their phospholipid molecules ensuring their membranes remain fluid in low temperatures

Notes…

• Relate the structure and function of triglycerides and phospholipids

• Page 16-18

(p) compare, with the aid of diagrams, the structure of a triglyceride and a phospholipid;

TriglycerideGlycerol plus three fatty acidsjoined by 3 ester bonds between the fatty acids and

the glycerolIn plants the fatty acids are unsaturated (many double

bonds) and the triglycerides are oilsIn animals the fatty acids are saturated (few or no

double bonds) and the triglycerides are more solidPhospholipidGlycerol plus two fatty acids and a phosphate group

joined by 2 ester bonds

(q) explain how the structures of triglyceride and phospholipid molecules relate to their functions

in living organisms;Triglyceride• Compact energy store, low mass to energy ratio (means mammals have to carry

less mass)• Insoluble in water (large non-polar molecules)• Does not affect cell water potential• Stored as fat providing insulation and protection• Provides buoyancy• Provides waterproofing (on feathers, leaves)• Source of water (from respiration – camel’s humps) • Provides electrical insulation around neurones • Helps in the absorption of fat soluble / A / D / E / K, vitaminsPhospholipid• Part hydrophilic (head), part hydrophobic (tail), so ideal basis for cell surface

membranes• Phosphate may have carbohydrate attached forming glycolipids involved in cell

signalling

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