Lipids Flashcards
What are the two types of lipids?
Triglycerides
Phospholipids
What are the bonds which form between lipids?
Ester bond
How many water molecules are formed when a triglyceride is formed?
The condensation reaction produces 3 ester bonds and 3 water molecules
When a hydrolysis reaction occurs what happens to the triglyceride?
It is split by the addition of 3 water molecules (which breaks the 3 ester bonds)
What do all lipids contain?
-Carbon
-Hydrogen
-Oxygen
What property of lipids means they cannot dissolve in water?
Lipids are insoluble because they are non-polar molecules so aren’t attracted to water
Why are lipids non-polar molecules?
The have a large number of carbon and hydrogen molecules
What type of substances are lipids soluble in?
They are soluble in other organic solvents like alcohol (eg. ethanol)
Where are triglycerides found?
They are component of our diet (in fats and oils) which are stored in fat cells in the body (adipose tissue)
What are triglycerides made from?
- One Glycerol
- 3 Fatty Acids
What forms a fatty acid?
- Long hydrocarbon chain
- Carboxyl Group (COOH)
Why aren’t lipids (triglycerides) polymers?
They are made from different sub units not similar repeating units (monomers)
What is the test for lipids?
- Mix the sample being tested with alcohol (ethanol) in a test tube
- Shake tube thoroughly and add cold water
- if a milky white emulsion is formed then this indicates the presence of a lipid
What is the positive result for the emulsion (lipids) test?
Milky white emulsion forms
What is a saturated fatty acid?
They only have single carbon to carb if bonds so form a linear hydrocarbon chain
What is an unsaturated fatty acid?
They have one or more carbon to carbon double bond which forms bent chains
What causes unsaturated fatty acid chains to bend?
Double carbon to carbon bond
Why do saturated fatty acids have a high melting point?
The intermolecular forces between the chains are strong and require a lot of energy to overcome
What property does a high melting point give saturated fatty acids?
It means they are solid at room temperature
Eg. Butter
Why do unsaturated fatty acids have a low melting point?
As the fatty acid chains are bent they form an irregular pattern and cannot fit tightly together.
This means the intermolecular attractions are weaker so are more easily broken
What property does a low melting point give unsaturated fatty acids?
It means they are liquid at room temperature
Eg. Vegetable Oils
Where are phospholipids found?
In cell membranes as a bilayer
Compare phospholipids structure to triglycerides?
Triglycerides are formed from one glycerol and 3 fatty acids
Phospholipids are formed from a phosphate group, glycerol and 2 fatty acids
Why are phospholipids polar molecules?
The phosphate group had a negative charge which means it’s slightly attracted to hydrogen molecules in water.
