1.5 Lipids Flashcards
What are the main groups of lipids?
Triglycerides and phospholipids
What are the roles of lipids?
Source of energy - when oxidised they provide lots of energy.
Waterproofing - as they are insoluble in water
Insulation - slow conductors of heat and help retain body heat
Protection - stored around delicate organs
What is a triglyceride made of?
glycerol and three fatty acids.
What type of bond does each fatty acid form with glycerol?
Ester bond
Why are triglycerides a good source of energy?
They have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms.
Why are lipids good storage molecules?
They have a low mass to energy ratio so lots of energy can be stored in a small volume
Why are triglycerides insoluble in water?
They are large and non-polar molecules
What is the advantage of lipids being insoluble?
Their storage does not affect osmosis in cells or the water potential of them.
What is a phospholipid made up of?
A hydrophilic head that attracts which interacts with water.
A hydrophobic tail which mixes readily with fat
What can phospholipids form in an aqueous environment?
A phospholipid bilayer
How does the phospholipid structure allow them to form glycolipids?
By combining with carbohydrates within the cell surface membrane.
Describe the difference between the structure of a triglyceride molecule and a phospholipid molecule.
In phospholipid, one fatty acid is replaced by phosphate.
Describe how you would test for the presence of a lipid in a food sample.
Add ethanol then add water.
White emulsion appears if lipid is present.
Describe how a saturated fatty acid is different from an unsaturated fatty acid.
Saturated - single bonds between carbons
Unsaturated - at least one double bond between carbon
Suggested why a fat substitute may not be digested in the gut by lipase?
The fat substitute is not complementary so no enzyme-substrate complex is formed
