lipids Flashcards
describe the test for lipids (2)
- add ethanol and shake
- add water and shake
- forms a milky emulsion
why are lipids not polymers
they don’t have repeating monomer units
describe the structure of a triglyceride molecule (1)
- glycerol molecule
- 3 fatty acid chains
what is an ester bond
a covalent bond formed between the OH of a glycerol molecule and the OH of a fatty acid in a condensation reaction
how many ester bonds are in a triglyceride
3
are fats solid or liquid at room temperature
solid e.g. butter
saturated, C-C
are oils solid or liquid at room temperature
liquid e.g. olive oil
unsaturated, C=C
what is a saturated fatty acid
fatty acid chain with no double carbon bonds (doesn’t include the carboxyl group)
define monoUNsaturated
fatty acid with one double carbon bond
define polyUNsaturated
fatty acid with multiple double carbon bonds
why are unsaturated triglycerides liquids at room temperature?
- they contain double carbon bonds
- double carbon bonds cause fatty acid tails to bend
- triglyceride molecules are further apart
- intermolecular force of attraction decreases, molecule is less compact
- less energy to overcome so it is liquid at room temperature
why are saturated triglycerides solid at room temperature?
- no double carbon bonds
- fatty acid tails don’t bend
- less space between molecules so stronger intermolecular forces of attraction
- more energy to overcome so solid at room temperature
why do triglycerides release lots of energy
there are lots of carbon-hydrogen bonds, these release energy when they break
why are triglycerides a good water source
they release water when they are broken down in respiration
are triglycerides polar or non-polar?
non-polar so they are insoluble
- don’t affect osmosis in cells
give 3 uses of lipids
- aquatic animals produce oil to waterproof their fur
- thermal & electrical insulation
- buoyancy
how are lipids like proteins?
they have a constant region (glycerol) and a variable region (fatty acid)
Describe the structure of a phospholipid (1)
- glycerol
- 2 fatty acids
- phosphate group
how does a phosphate group join a glycerol molecule
- condensation reaction
- between OH on glycerol and OH on phosphoric acid
- creates a phosphate ester bond
is the phospholipid head hydrophobic or hydrophilic?
hydrophilic
- has a negative charge
- attracts H+ in water
what are micelles
circular formations that are made up of phospholipid tails
describe phospholipid bilayer
- hydrophilic heads face outwards towards the water
- hydrophobic tails face inwards away from water
how are membranes fluid
because phospholipids can move around each other- allows the cell to change shape
give 2 roles of the bilayer
- controls what leaves/ enters the cell
- electrical insulation- does not let ions or water in as the fatty acid tails are hydrophobic and non-polar
give 5 functions of lipids
- phospholipids provide flexibility to membranes
-thermal insulation- slow conductors of heat and retain body heat
-electrical insulation- in myelin sheath around nerve cells
-protection- fat around organs such as kidney
-insoluble- used for waterproofing, waxy lipid cuticle to prevent water loss
-energy source- when oxidised they release energy
describe 2 features which make lipids suitable for their function
- lots of energy stored in a small mass- good for animals as they can reduce the mass they carry around
-lots of energy stored in C-H bonds
- they are large and non-polar so insoluble and dont affect water potential so no bursting
-release water when oxidised so act as a water source
what is the difference between a phosphate molecule and a fatty acid molecule
phosphate is hydroPHILIC and attracts water
fatty acid is hydroPHOBIC and repels water
describe the structure of a phospholipid
- hydrophilic head- attracts water
-hydrophobic tail- repels water
describe a control that could be used during a test for lipids
- instead of adding ethanol and water to the sample, replace the sample with water
- solution should stay clear
list 2 differences between a triglyceride molecule and a phospholipid molecule (2)
- triglyceride has 3 fatty acids
- phospholipid has 2 fatty acids, 1 phosphate group
or
- triglyceride is non polar
- phospholipid is polar
explain why phospholipids form a bilayer but triglycerides don’t (3)
- phospholipids have both hydrophobic and hydrophilic regions
- triglycerides are just hydrophobic- non-polar
- phospholipid heads attract to water, fatty acid tails repel water
compare and contrast the structure and properties of triglycerides and phospholipids (5)
- both have glycerol
- both have ester bonds
- triglycerides have 3 fatty acids, phospholipids have 2 fatty acids and a phosphate group
- both are insoluble in water
- triglycerides are non-polar and phospholipids have hydrophilic and hydrophobic regions
- both have C,H,O but phospholipids also have P
