1.3 Lipids Flashcards
Structure of triglycerides:
condensation of 1 glycerol and 3 fatty acids forming ester bond
Are lipids non-polar or polar?
Non-polar
Are lipids hydrophobic or hydrophilic?
Hydrophobic
What are the two groups of lipids?
Triglycerides and phospholipids
Structure of triglycerides:
1 glycerol and 3 fatty acids
In triglycerides, what are the glycerol and the 3 fatty acids held together by?
Ester bonds
Triglycerides are good for energy __________
storage
How does the structure of triglycerides help them to be good for energy storage?
- The long fatty acid chains contain many C-H bonds
- so when triglycerides are oxidised, the bonds break
- releasing energy
Triglycerides are useful for the storage of ________
water
How does the structure of triglycerides make them useful for water storage?
- Triglycerides are hydrophobic
- so they do not cause water uptake in cells
Triglycerides are useful for I_____________
insulation
Why are triglycerides make them useful for insulation?
- Form part of the myelin sheath that surrounds nerve fibres
- increase the speed of nerve impulses
Triglycerides are useful for P______________
protection
Why are triglycerides useful for protection?
- The adipose tissue in mammals contains stored triglycerides
- this tissue helps to protect organs from the risk of damage
How are triglycerides formed?
By esterification
What is esterification?
The formation of an ester bond in a condensation reaction
What are the components of phospholipids?
- Glycerol backbone
- 2 fatty acid chains
- A phosphate (PO4) group
Are the fatty acid chains in phospholipids hydrophobic or hydrophilic?
Hydrophobic
Is the phosphate head in phospholipids hydrophobic or hydrophilic?
Hydrophilic
Do phospholipids contain both a saturated and unsaturated fatty acid chain?
YES
What is a saturated fatty acid?
- Does NOT contain any double bonds
- The chains will be STRAIGHT
What is an unsaturated fatty acid?
- DOES contain double bonds between (some) carbon atoms
- Fatty acid chains will be kinky
What is the method for the test for lipids?
- Add 5cm3 of ethanol to the sample
- Shake to dissolve any lipid in the ethanol
- THEN add 5cm3 of water + shake
What is the positive result for the test for lipids?
A cloudy-white emulsion
What is the test for lipids called?
Emulsion
The general structure of a fatty acid is RCOOH. Name the group represented by COOH.
Carboxylic acid
Describe how you would test for the presence of a lipid in a liquid sample of food.
- Add ethanol and shake
- Add water and shake
- White emulsion
Describe how a triglyceride molecule is formed.
- One glycerol and three fatty acids
- 3 condensation reactions and removal of three molecules of water
- 3 ester bonds formed
The structure of a phospholipid molecule is different from that of a triglyceride. Describe how a phospholipid is different.
- Phosphate group
- Has 2 fatty acids (instead of 3)
Describe how a saturated fatty acid is different from an unsaturated fatty acid.
- Saturated = single bonds between carbons
- Unsaturated = double bonds between carbons
Which of the fatty acids, X or Y, in the figure above is unsaturated
Contains double bond between (adjacent) carbon atoms in hydrocarbon chain.
The scientists expressed their results as Percentage of lipid in plasma membrane by mass. Explain how they would find these values.
mass of each lipid/ mass of all lipids x 100
what is special about the R group of fatty acid
R-group of a fatty acid may be saturated or unsaturated
What quality does hydrocarbon ‘tails’ give to fatty acids?
It makes them insoluble in water because the tails are hydrophobic.
How are phospholipids similar to triglycerides?
Contrast saturated and unsaturated fatty acids.
Saturated:
Contain only single bonds
Straight-chain molecules have many contact points
Higher melting point = solid at room temperature
Found in animal fats
Unsaturated:
Contain C=C double bonds
‘Kinked’ molecules have fewer contact points
Lower melting point = liquid at room temperature
Found in plant oils
Compare phospholipids and triglycerides.
Both have glycerol backbone.
Both may be attached to a mixture of saturated, monounsaturated & polyunsaturated fatty acids.
Both contain the elements C, H, O.
Both formed by condensation reactions.
contrast phospholipids and triglycerides.
phospholipids:
2 fatty acids & 1 phosphate group attached
Hydrophilic head & hydrophobic tail
Used primarily in membrane formation
triglycerides:
3 fatty acids attached
Entire molecule is hydrophobic
Used primarily as a storage molecule (oxidation releases energy)
