1.5 Lipids Flashcards
What are the characteristics of lipids
Contain carbon, H , Oxygen
Insoluble in water
Soluble in organic solvents
What are the roles of lipids
It is a source of energy, when oxidised lipids provide twice as much energy as the same mass of c.drates and release valuable water
Waterproofing, their insolubility in water is useful. Plants and insects have wavy lipid cuticles that conserve water
Insulation fat are slow conductors of heat
Protection
What is a triglyceride
They have three fatty acids combined with glycerol.
Each fatty acid forms an ester bond with glycerol in a condensation reaction.
Define saturated
All carbon atoms are linked to the maximum number of hydrogen atoms, they are full of hydrogen
Define unsaturated
There is a double bond therefore carbon cannot hold the maximum number of hydrogen
What is the effect of a double bond in carbon atoms
The d bike bonds cause the molecule to bend, therefore they cannot pack together closely making them liquid at room temperature
The structure of triglycerides related to their properties
Triglycerides have a high ration of energy-storing carbon-hydrogen bonds to carbon atoms therefore are an excellent source of energy
Triglycerides gave low mass to energy ratio
Large non polar molecules therefore they are insoluble in water so it does not affect osmosis or the water potential
Have high ratio of hydrogen to oxygen atoms, try.cides release water when oxidised and therefore provide an important source of water
What is the structure of a phospholipid
It has a phosphate molecule and two fatty acids
Which area is hydrophilic ad hydrophobic on a phospholipid
It has a hydrophilic head which interacts with water
Hydrophobic tail it mixes readily with fat, not with water
The structure of phospholipids related to their properties
Phospholipids are polar molecules. This means that in an aqueous environment, phospholipid molecules form a bilateral within cell-surface membranes, as a result a hydrophobic barrier is formed between the inside and outside of a cell
The hydrophobic head help to hold at the surface of the cell surface membrane
Phospholipid structure allows them to form glycolipids by combining with c.dates within the cell surface membrane. These glycolipids are important in cell recognition
Test for lipids
Take a completely dry and grease free test tube to 2cm^3 of sample being tested
Add 5cm^3 of ethanol
Snake the tube thoroughly to dissolve lipid
Add 5cm^3 of water and shake
A cloud white colour indicates a presence of lipid
A
As control repeat with water
