Lipids Flashcards
What makes up a lipid?
A high number of carbon and hydrogen atoms and a low number of oxygen atoms
What common features do lipids have?
- Insoluble in water
- soluble in alcohol
- not polymers, they are macromolecules as no repeating units
What is the structure of a triglyceride?
3 hydrocarbon chains derived from fatty acids that are ester bonded to one molecule of glycerol
What is an unsaturated fatty acid? How is it arranged?
- has one or more carbon carbon double bonds
- causes kinks in the chains so they cant pack tightly together
- this means more unsaturated fatty acids cause weak IMF / Van der Waals
What is a saturated fatty acid? How is it arranged?
- has no carbon carbon double bonds
- so chains pack tightly
- so strong IMF/ Van der Waals
What makes up the ester bond?
the carbon of the glycerol bonded to an oxygen bonded to a carbon, double bonded to an oxygen
What is the function of a triglyceride?
- Great energy source due to high ratio of c-h bonds
- great energy store as its insoluble, doesn’t affect water potential
- provides heat and electrical insulation
- waterproofing
- protects organs
What is the structure of a phospholipid?
2 hydrocarbon chains derived from fatty acids that are ester bonded to one molecule of glycerol which is ester bonded to a phosphate group
What properties does a phospholipid have?
- it is amphipathic which means it has a hydrophobic tail and a hydrophilic head
- this causes it to form phospholipid bilayers and micelles in water
- it can form a fluid mosaic
- bacteria have more proteins in the membrane
- it is selectively permeable, only small non polar molecules can pass through it
What is cholesterol? Why is important?
- A steroid and a lipid
- contains no fatty acid or glycerol
- made of 4 isoprene units
- small and hydrophobic
- can sit in the hydrophobic layer of the phospholipid bilayer
- regulates fluidity
- made in the liver
- can make testosterone, oestrogen and vitamin D which can also pass through PBL
what is the test for lipids?
- shake sample with alcohol
- combine with water
- if it turns cloudy white then its positive
Why does the emulsion test produce a cloudy white substance?
- lipids are insoluble in water and soluble in ethanol
- After lipids have been dissolved in ethanol and then added to H2O, they will form tiny dispersed droplets in the water. This is called an emulsion.
- These droplets scatter light as it passes through the water so it appears white and cloudy.
