Lipids Flashcards
What’s the roles of lipids
In the cell membranes. Phospholipids contribute flexibility of membranes and then transfer of lipid soluble substances across them
Source of energy - when oxidised, lipids provide energy ( more then twice then carbohydrates)
Waterproofing - insoluble in water and therefore useful as a waterproofing.
Insulation - fats are slow conductors of heat and when stored beneath the body surface help to retain body heat
Protection - fat is often stored around delicate organs
What’s the structure of triglycerides
3 fatty acids combine with glycerol.
Each fatty acid forms an ester bond with glycerol in a condensation reaction
What does hydrolysis of a triglyceride produce
Glycerol and 3 fatty acids
What’s a saturated fatty acids
No double bonds between carbon atoms
What’s a unsaturated fatty acid
Double bond between the carbon atoms
How does the structure of triglycerides relate to their properties
Have high ratio of energy - storing carbon - hydrogen bonds to carbon atoms and therefore an excellent source of energy
Have low mass to energy ratio - good storage molecules because much energy can be stored in a small volume.
Being large, non polar molecules - insoluble in water, as a result their storage does not affect osmosis in cells or the water potential of them
Have high ratio of hydrogen to oxygen atoms - they release water when oxidised and therefore provide an important source of water
What’s the structure of a phospholipid
2 fatty acids, glycerol and a phosphate molecule
What are phosphate and fatty acids like towards water
Phosphate- hydrophilic - attracts water
Fatty acids - hydrophobic - repel water
What two parts is a phospholipid made up of
Hydrophilic head - interacts with water but not with fat
Hydrophobic tail- orients itself away from water but mixes readily with fat
What are phospholipids like when they are placed in water
They position themselves so that the hydrophilic heads are as close to the water as possible and the hydrophilic tails are as far away from the water as possible
How is the structure of phospholipids related to their properties
Polar molecules - in an aqueous environment, they form a bilayer within cell surface membranes - a hydrophobic barrier is formed between the inside and outside of a cell
Hydrophilic phosphate heads - help hold at the surface of the cell membrane
Phospholipid structure- allows them to form glycolipids by combining with carbohydrates within the cell surface membrane. Their important in cell recognition
What’s the test for lipids
Add 2cm of sample, add 5 Cm of ethanol
Shake tube
Add 5 Cm of water and shake gently
Cloudy white colour if positive
