Lipids Flashcards
Are lipids polymers?
No, they are not made of similar repeating units.
What are the two types of lipids?
Triglyceride and phospholipids
What are uses of lipids?
- Plasma membrane
- Energy
- Protection
- Hormones
- Insulation
- Waterproofing
Where are triglycerides usually found?
In food
Where are phospholipids usually found?
Within cell membranes
What is the structure of triglycerides?
How do they interact with water?
They are made of one molecule of glycerol linked to three fatty acids. They are hydrophobic and insoluble in water.
How are the fatty acids joined to the glycerol in lipids?
What bonds?
Condensation reaction forms ester bonds
Water is produced.
What is the difference between saturated and unsaturated fatty acids?
Saturated fatty acids don’t have any double bond between carbons in the hydrocarbon chain while unsaturated fatty acids do
What is the structure of fatty acids?
They have a carboxylic group ( C single bonded to OH and double bonded to O) bonded to a hydrocarbon tail.
What are the properties of triglycerides?
- Energy storage molecule - hydrocarbon tails of the fatty acids contain lots of chemical energy
- Insoluble in water - so doesn’t affect the water potential.
What is the structure of a phospholipid?
Glycerol molecule bonds to a phosphate and two fatty acids
What are the features of phospholipids?
The phosphate group has a negative charge, whereas the fatty acid tails have no charge. This makes the phosphoglycerol head hydrophilic and the fatty acid tails hydrophobic.
This allows for a bilayer to be formed in water.
How do you test for lipids?
The Emulsion Test
1. Crush sample if needed
2. Add ethanol and shake
3. Add water in drops
4. If lipids present, a white emulsion will form
Q2. Compare and contrast the structure and properties of triglycerides and phospholipids. (5)
Both contain ester bonds
Both contain glycerol
Both are able to have saturated or unsaturated fatty acids
Both are insoluble in water
Triglyceride has three fatty acids and phospholipid has two fatty acids plus phosphate group;
Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
Phospholipids form bilayer (in water) but triglycerides don’t;
Q4.
b) Explain why triglycerides are not considered to be polymers.
They do not contain repeating molecules.
