Lipids Flashcards
Describe the common properties of all lipids
All contain hydrogen oxygen and carbon, all are insoluble in water, proportion of oxygen to carbon and hydrogen is smaller, all are soluble in organic solvents such as alchohols
Describe the roles of all lipids
-Key source of energy because when they are oxidised lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water
-Waterproofing because lipids are insoluble e.g plants have waxy cuticles
-Insulation for example fats have a very slow conduction of heat and can be stored to retain body heat
-Protection, fat is often stored around these organs
Describe the structure of triglycerides
They have one molecule of glycerol with three molecules of fatty acids attatched
How are triglycerides formed?
Each fatty acid forms an ester bond with glycerol during a condensation reaction , removing water.
What are the differences in the properties of fats and oils caused by?
Variations in the fatty acids. All fatty acids have a carboxyl group with a hydrocarbon chain attached.
What does saturated mean?
When there are no double carbon bonds in the hydrocarbon chain, all carbon atoms are linked to the maximum hydrogen atoms.
What does mono-unsaturated mean?
When there is a single double carbon bond in the hydrocarbon chain
What does poly-unsaturated mean?
When more than one double carbon bond is present in the hydrocarbon chain
How does the structure of lipids relate to their function?
High ratio of energy storing carbon hydrogen bonds to carbon atoms so they are an excellent source of energy
- Low mass to energy ratio makes them good energy molecules because lots of energy can be stored in a low volume
-Large and non polar so they are insoluble in water meaning their storage does not effect osmosis of cells
-High ratio of oxygen to hydrogen atoms so they release water when oxidised providing an important source of water
Whats the difference between phospholipds and lipids?
They are similar apart from in a phospholipid one fatty acid molecule is replaced with a phosphate molecule
Describe the structure of a phospholipid
They have a hydrophilic head with a hydrophobic tail so it is a polar molecule, the hydrophobic tail stays as far away from water as it can
Describe how we test for lipids
Take a completely dry test tube, and add 2cm cubed of the sample being tested and 5 cm cubed of ethanol and shake the tube properly to dissolve any liquid in the sample. Then add 5cm cubed of water and shake gently. A white milky emulsion indicated the presence of a lipid. Then do it again with water instead of the sample as a control.
