1.3 Lipids Flashcards
1
Q
Name two groups of lipids
A
- triglycerides and phospholipids
2
Q
Describe the structure of a fatty acid (RCOOH)
A
- variable R-group - hydrocarbon chain (could be saturated or unsaturated)
- COOH = carboxyl group
3
Q
Describe the difference between saturated and unsaturated fatty acids
A
- saturated = no C=C double bonds in hydrocarbon chain - all carbons fully saturated with hydrogen
- unsaturated = one or more C=C double bonds in hydrocarbon chain (creating a bend / link)
4
Q
Describe how triglycerides form
A
- 1 glycerol and 3 fatty acids
- 3 condensation reactions
- removing 3 water molecules
- forming 3 ester bonds
5
Q
Explain how the properties of triglycerides are related to their structure
A
- function - energy storage
- high ratio of C-H bonds to carbon atoms in hydrocarbon chain
- so used in respiration to release more energy than the same made of carbohydrates
- hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards)
- so no effect on water potential of cell (or can be used for waterproofing)
6
Q
Describe the difference between the structure of triglycerides and phospholipids
A
One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
7
Q
Describe how the properties of phospholipids relate to their structure
A
- function - form a bilayer in cell membrane, allowing diffusion of lipid-soluble (non-polar) or very small substances and restricting movement of water-soluble (polar) or larger substances
- phosphate heads are hydrophilic
- attracted to water so point to water ( aqueous environment ) either side of membrane
- Fatty acid tails are hydrophobic
- Repelled by water so point away from water / to interior of membrane
8
Q
Describe the test for lipids
A
- Add ethanol, shake (to dissolve lipids), then add water
- Positive result = milky white emulsion
