This is my mind map: '1.5 Lipids'. Its is based on the AQA A-Level Biology specification, and it is also based on the AQA Biology A -Level 2nd edition textbook. Find my matching 'Lipids' Flashcards on my profile, or follow the link here: https://www.goconqr.com/en-US/p/4819666
Each fatty acid forms an ESTER bond with glycerol in a CONDENSATION
REACTION
Glycerol molecule is same in all moleculets but
there are variations in the fatty acids meaning
there are different properties
Saturated = NO carbon-carbon double
bonds
Mono-unsaturated = 1 double
bond
Polyunsaturated = More than 1 Double
bond
High ratio of energy-storing Carbon-hydrogen bonds to carbon atoms = excellent source
of energy
Low mass to energy ratio = good storage
molecules. Beneficial to animals as
reduced mass to carry around
Large, non-polar and insoluble = doesn't
effect osmosis in cells or water potential
in them
Triglycerides release water when oxidised, meaning
they're an important source of water for organisms,
especially those living in dry conditions
PHOSPHOLIPIDS
Similar to triglycerides but
one fatty acid replaced with
a PHOSPHATE MOLECULE
Fatty acid molecules - Hydrophobic 'tail'
Phosphate Molecules - Hydrophillic 'head'
Polar
Properties
Polar so form a bilayer between
intercellular and extra cellular
Phospholipid structure allows them to form glycolipids by combining
with carbohydrates within the cell-surface membrane. These glycolipids
are important in cell recognition
Characteristics
Contain: Carbon, Oxygen and Hydrogen
Proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
Soluble in solvents such as alcohols and acetone
Insoluble in water
Roles of Lipids
Source of Energy
When oxidised, lipids provide over 2x the energy of
carbohydrates
Waterproofing
Lipids are insoluble = good at waterproofing.
Both plants and insects have
waxy, lipid cuticles that
conserve water. Where as
mammals produce an oily
secretion from the
sebaceous glands in the skin
Insulation
Fats are slow conductors of heat
meaning when stored they help retain
body heat. They also act as electrical
insulators in the myelin sheath around
nerve cells
Protection
Fat is often stored around delicate organs
Testing For Lipids
Dry and grease-free testube
Add sample and ethanol
Shake tube throughly and dissolve lipid in sample
Add water, shake gently
Cloudy white = lipid present and emulsion formed
As a control, repeat the procedures using after
instead of the sample; the final solution should
be clear