lipids Flashcards
list the 2 types of lipids
phospholipids
triglycerides
list the 5 roles of lipids
cell membranes (phospholipids)
due to them being flexible
energy source
release 2x energy of carbohydrates
protection
waxy cuticle
oils from sebaceous glands in skin
insulation
warmth and myelin sheath around neurons allows electrical impulses to be transmitted quickly
list 3 characteristics of lipids
C H O (but less than in carbohydrates)
insoluble in water
soluble in organic solvents (alcohol)
describe the general structure of triglycerides
1 glycerol
3 fatty acids
what stays constant in all triglycerides and what changes
all triglycerides have 3 fatty acids
but the structure of the hydrocarbon tail can change
what are the 2 types of fatty acid
saturated fatty acid
unsaturated fatty acid
what are the 2 types of unsaturated fatty acids and what do they mean
mono
1 c=c
poly
many c=c
when you join a fatty acid with a glycerol molecule what kind of reaction is it?
condensation reaction
describe the test for lipids
EMULSION TEST
1. take a dry and grease free test tube
2. 2cm^3 of sample to 5cm^3 of ethanol
3. shake the tube to dissolve any lipid
4. add 5cm^3 of water and shake gently
5. white emulsion shows the presence of lipids
list 4 properties of triglycerides and explain why they are advantages
- insoluble in water (large non-polar molecules)
= doesn’t affect osmosis in cells - low mass to energy ratio
= good storage molecules because a lot of energy can be stored in a small volume) - a high ratio of energy storing carbon to hydrogen bonds
= excellent source of energy when bonds are broken - a high ratio of hydrogen to oxygen atoms
= release water when oxidized therefore are important sources of water for organisms in a desert
what type of molecules are phospholipids
phospholipids are polar molecules
describe the general structure of phospholipids
2 fatty acids and 1 phosphate group
what does fatty acids being hydrophobic mean
fatty acids are hydrophobic this means they hate water
