3.1.3 - Lipids
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13 Terms
What are the two examples of lipids?
Triglycerides
Phospholipids
How are triglycerides formed?
In a condensation reaction with one molecule of glycerol and three fatty acids chains (therefore 3 condensation reactions for each fatty acid chain)
How are phospholipids formed?
In a condensation reaction with one molecule of glycerol, two fatty acid chains and a phosphate group
Name the bond formed and between which molecules it is formed in a lipid?
Ester bond
Between glycerol molecule and fatty acid chain
How many molecules of water are made in the condensation of a triglyceride?
3 water molecules
What is an R group?
A variable group on a lipid
What are the properties of triglycerides? (4 points)
Energy storage
Metabolic water source (can release water if oxidised)
Large and hydrophobic therefore insoluble in water
Low mass
How do these properties make triglycerides efficient? (4 points)
Energy storage - when energy is needed it can be hydrolysed and used
Metabolic water source - when hydrolysed they release water which is needed for respiration
Insoluble in water - water potential doesn’t change so cells don’t shrivel or burst
Low mass - large amount can be stored without increasing mass and therefore preventing movement
The head of a phospholipid is polar, what does this mean for water molecules and other lipids?
Water - can interact with water (hydrophilic)
Lipids - repels lipids
Are the fatty acid tails polar or non-polar and what does this mean for water molecules and other lipids?
Non-polar
Water - repels water (hydrophobic)
Fats - interacts with lipids
How do phospholipids arrange themselves in aqueous environments?
The hydrophilic heads face outward towards the water whereas the hydrophobic tails face inwards away from the water
What structure does this arrangement form?
Phospholipid bilayer - plasma cell membrane
What is the test for lipids?
Mix the sample in ethanol
Then add water
Positive test = a white emulsion forms