save my exams lipids Flashcards
what are lipids
Macromolecules which contain carbon, hydrogen and oxygen atoms
contain lower o2 than carbs
Non-polar and hydrophobic
insoluble in water
two types of lipids
1)phospholipids
2)triglycerides
non polar
when electrons are shared equally so aren’t charged
triglycerides
non-polar, hydrophobic molecules
glycerol and fatty acids
contain a methyl group at one end of a hydrocarbon chain known as the R group
other is a carboxyl group
RCOOH
how do fatty acids vary
Length of the hydrocarbon chain (R group)
(R group) may be saturated
or unsaturated
polyunsaturated
more than one double carbon
how triglycerides are formed
-formed by esterfication
-An H from glycerol combines with an OH from the fatty acid to make water
-The formation of an ester bond is a condensation reaction
-For each ester bond formed a water molecule is released
-Three fatty acids join to one glycerol molecule to form a triglyceride
-Therefore for one triglyceride to form, three water molecules are released
why triglycerides are energy reserves
they store more energy per gram due to their hydrocarbon chains
triglyceride functions
Energy storage
Insulation
Buoyancy
Protection
Energy storage
-when triglycerides are oxidised during cellular respiration this causes these bonds to break releasing energy used to produce ATP
- therefore store more energy per gram than carbohydrates and proteins
hydrophobic
-do not cause osmotic water uptake in cells so more can be stored
The oxidation of the carbon-hydrogen bonds
-releases large numbers of water molecules (metabolic water) during cellular respiration
-Desert animals retain this water if there is no liquid water to drink
Bird and reptile embryos in their shells also use this water
Insulation
myelin sheath
provides insulation which increases the speed of transmission of nerve impulses
Buoyancy
low density of fat tissue increases the ability of animals to float more easily
Protection
tissue in mammals contains stored triglycerides and this tissue helps protect organs from the risk of damage
structure of phospholipids
-two fatty acids bonded to a glycerol molecule in a phospholipid as one has been replaced by a phosphate ion
-phosphate is polar it is soluble in water
-fatty acid ‘tails’ are non-polar and therefore insoluble in water
presence of hydrophobic fatty acid tails
-hydrophobic core is created when a phospholipid bilayer forms
This acts as a barrier to water-soluble molecules
-
hydrophilic phosphate heads
-forms h bonds
-This enables the cells to organise specific roles into organelles helping with efficiency
saturated fatty acids
-each carbon atom in the hydrocarbon tail (except for the final carbon atom) is bonded to two hydrogen atoms
-carbon atoms in the hydrocarbon tail are all single bonds
unsaturated fatty acids
at least one carbon-carbon double bond
cause the hydrocarbon tail of unsaturated fatty acids to kink
not as straight as saturated fatty acids
does not contain the maximum number of hydrogen atoms possible
each carbon atom in a carbon-carbon double bond can only bond to one hydrogen atom
properties of triglycerides
energy storage molecules
insoluble
peroperties of phospholipids
phosphate group is hydrophilic
centre of the phospholipid bilayer is hydrophobic
energy storage
hydrocarbon tails of the fatty acids in triglycerides contain large amounts of chemical energy, which can be released when the fatty acids are broken down
insoluble
they don’t affect the water potential inside the cell
