Lipids Flashcards
Are lipids polymers?
- No
- They are made from different small units and not a repeating pattern
What elements are lipids made up of?
- CHO
- (sometimes) phosphorous
What are the functions of lipids?
- Store of energy
- Thermal insulator
What does hydrophobic mean?
Repelled by water, will form droplets
What are the two types of lipids?
Triglycerides and Phospholipids
What is the structure of Triglycerides?
3 long hydrocarbons (fatty acids) joined to glycerol
What does saturated mean?
‘full of hydrogen’ - no double bonds in hydrocarbon chain
What does unsaturated mean?
‘not enough hydrogen’ - contains 1 or more double bonds in hydrocarbon chain
What are the characteristics of saturated fatty acids?
- no double bonds in chain
- straight (no kink)
- high melting point so solid at room temp
What are the characteristics of unsaturated fatty acids?
- double bonds in chain
- bendy (have a kink)
- low melting point so liquid at room temp
What type of reaction forms triglycerides?
Condensation
What bond forms between -OH groups in triglycerides?
Ester bond
Describe the formation of triglycerides
- Bond forms between two -OH groups
- Leaves one oxygen to form the ester bond
- Forms 3 waters + 3 ester bonds
What is the test for lipids?
Emulsion test
What is the structure of Phospholipids?
- Glycerol + 2 fatty acids
- Phosphate group (1 fatty acid substituted)
- Contains ‘kink’ (C=C double bond, unsaturated)
What does hydrophilic mean?
Attracts water
How are phospholipids both hydrophobic and hydrophilic?
- tail = hydrophobic (fatty acids)
- head = hydrophilic (phosphate + glycerol)
Explain why a phospholipid has both hydrophobic and hydrophilic regions.
• hydrophilic head - the phosphate group has a negative charge and so attracts water
• hydrophobic tail - since the fatty acids have no charge and so repel water
How does triglycerides being non-polar make them ideal for their function?
Makes them insoluble in water so are ideal storage compounds as they are osmotically inactive
What function is linked to triglycerides having a high ratio of hydrogen to oxygen atoms?
Releasing water when respired - important for organisms in dry deserts
Why do triglycerides release twice as much energy as carbohydrates during aerobic respiration?
They possess a high proportion of carbon-hydrogen bonds
