lipids Flashcards
3.1.3
describe what lipids are
lipids are fats and oils
fats are solid at room temperature
oils are liquid at room temperature
what elements are lipids made of?
- C, carbon
- H, hydrogen
- O, oxygen
- sometimes P (if phospholipids)
what are triglycerides composed of?
- glycerol
- 3 fatty acids
structure of triglycerides
H ** O ** ester bond
| ||
H - C - O - C - R
| O
| ||
H - C - O - C - R
| O
| ||
H - C - O - C - R
|
H
what kind of reaction is the formation of a triglyceride molecule?
a condensation reaction, since (3) water molecules are released and the bonds formed are called ester bonds.
what are the two types of fatty acids?
- unsaturated, the fatty acid has one or more carbon-carbon double bonds in its structure
- saturated, the fatty acid has no carbon-carbon double bonds in its structure and all of the C atoms are fully ‘saturated’ with H atoms
explain why triglycerides containing unsaturated fatty acids tend to be liquid at room temperature?
the carbon-carbon double bonds in unsaturated fatty acids makes a kink in the chain, it means the molecules do not pack together so tightly and so the intermolecular forces are weaker as a result
what are the properties of triglycerides
triglycerides are non-polar molecules because of their long hydrocarbon chains, this means that they are insoluble in water
what are the functions of triglycerides?
- source of energy/long term energy storage. more dense isn’t used till we’ve used all glucose and glycogen
- used as insulation, poor conductor of heat
- used as a layer of protection for the organs below
- waxy cuticle to prevent water loss through osmosis
- insoluble
whats the structure of phospholipids?
they are composed of glycerol, phosphate and fatty acids
how is the structure of a phospholipid different to the structure of a triglyceride?
the 3rd fatty acid on a triglyceride is replaced by a phosphate
properties of a phospholipid
- a polar, hydrophilic head (which interacts with water)
- a non-polar hydrophobic tails (which does not interact with water)
whats the functions of a phospholipid?
- phospholipids are the main component of cell membranes, since the inside of the cell is an aqueous solution and so is the outside of the cell, the phospholipids arrange themselves into a phospholipid bilayer
whats the test for lipids?
emulsion test
add ethanol, add water and shake
if lipids are present a white cloudy emulsion will appear