1.2 (biological molecules) Flashcards
lipids
lipids are macromolcules which contain what atoms
- carbon
- hydrogen
- oxygen
unlike carbohydrates lipids contain a lower proportion of
oxygen
the two groups of lipids are
- triglycerides (the main component of fats and oils)
- phospholipids
triglycerides are non polar and what molecules
hydrophobic
the monomers of triglycerides are
- glycerol
- fatty acids
glycerol is an alcohol meaning that it is an
- it is an organic molecule
glycerol is an alcohol meaning that it is an organic molecule that contains
a hydroxyl group bonded to a carbon atom
what kind of chain do fatty acids have
hydrocarbon
fatty acids contain a what group at one end of a hydrocarbon chain
methyl
what are the two groups at either end of a lipid
- methyl group CH3
- carboxyl group COOH
the hydrocarbon chain of a lipid is known as what group
R group
the shorthand chemical formula for a fatty acid is
RCOOH
fatty acids can vary in what two ways
- length of the hydrocarbon chain (R group)
- the fatty acid chain (R group) may be saturated (mainly in animal fat) or unsaturated (mainly vegetable oils, although there are exceptions e.g. coconut and palm oil)
unsaturated fatty acids can be what two types of unsaturated
mono or poly-unsaturated
if H atoms are on the same side of the double bond in a fatty acid then it is a
- cis-fatty acids
- metabolised by enzymes
if H atoms are on opposite sides of the double bond in a fatty acid then it is a
- trans-fatty acid and cannot form enzyme-substrate complexes
- therefore not metabolised by enzymes
- they are linked with coronary heart disease
what type of unsaturated fatty acid can be metabolised by enzymes
cis-fatty acids
what type of unsaturated fatty acid cannot be metabolised by enzymes
trans-fatty acids
trans-fatty acid cannot form
- enzyme-substrate complexes
- therefore not metabolised by enzymes
what type of unsaturated fatty acid is linked with coronary heart disease
- trans-fatty acids
triglycerides are formed by
esterification
an ester bond forms when a what group on glycerol bonds with the what group of the fatty acid
- hydroxyl (-OH)
- carboxyl (-COOH)
- (an ester bond forms when a hydroxyl (-OH) group on glycerol bonds with the carboxyl (-COOH) group of the fatty acid)
the formation of an ester bond is a what reaction
condensation
for each ester bond formed a what molecule is released
water
three fatty acids join to one glycerol molecule to form a triglyceride, therefore for one triglyceride to form, how many water molecules are released
three
what are the four main functions of a triglyeride
- energy storage
- insulation
- buoyancy
- protection
as triglycerides are hydrophobic they do not cause
- osmotic water uptake in cells
- so more can be stored
plants store triglycerides in the form of what where
- oils
- in their seeds and fruits
if triglycerides oils are extracted from seeds and fruits these are generally liquid at room temperature due to the presence of
- double bonds
- which add kinks to the fatty acid chains altering their properties
mammals store triglycerides as what where
- oil droplets
- in adipose tissue to help them survive when food is scarce (e.g. hibernating bears)
the oxidation of the carbon-hydrogen bonds releases large numbers of what during what
- water molecules (metabolic water) - during cellular respiration
desert animals retain what water if there is no liquid water to drink
metabolic water
bird and reptile embryos in their shells also use what water
metabolic water
triglycerides are part of the composition of the what that surrounds nerve fibres
myelin sheath
triglycerides are part of the composition of the myelin sheath that surrounds nerve fibres, this provides insulation which increases
the speed of transmission of nerve impulses
triglycerides compose part of the what tissue layer below the skin which acts as insulation against heat loss (eg. blubber of whales)
adipose
the low density of fat tissue increases the ability of animals to
float more easily
the adipose tissue in mammals contains stored triglycerides and this tissue helps protect organs from
the risk of damage
phospholipids are a type of lipid, therefore they are formed from the monomer what and what
glycerol and fatty acids
in a phospholipid how many fatty acids are bonded to a glycerol molecule
two
unlike triglycerides, there are only two fatty acids bonded to a glycerol molecule in a phospholipid as one has been replaced by a
phosphate ion (group)
as the phosphate of a phospholipid is what it is what in water
- polar
- soluble in water (hydrophilic)
the fatty acid ‘tails’ of a phospholipid are what it is what in water
- non-polar
- insoluble in water (hydrophobic)
phospholipid diagram
phospholipids are the major components of cell
surface membranes
phospholipids have both hydrophobic and hydrophilic parts and so are
amphipathic
as a result of having hydrophobic and hydrophilic parts phospholipid molecules form what in water
monolayers or bilayers in water
role of phospholipids (5)
- the main component (building block) of cell membranes
- due to the presence of hydrophobic fatty acid tails, a hydrophobic core is created when a phospholipid bilayer forms: this acts as a barrier to water-soluble molecules
- the hydrophilic phosphate heads form H-bonds with water allowing the cell membrane to be used to compartmentalise: this enables the cells to organise specific roles into organelles helping with efficiency
- composition of phospholipids contributes to the fluidity of the cell membrane: if there are mainly saturated fatty acid tails then the membrane will be less fluid; if there are mainly unsaturated fatty acid tails then the membrane will be more fluid
- phospholipids control membrane protein orientation: weak hydrophobic interactions between the phospholipids and membrane proteins hold the proteins within the membrane but still allow movement within the layer
phospholipids are the main component (building block) of
cell membranes
due to the presence of hydrophobic fatty acid tails, a
- hydrophobic core is created
- when a phospholipid bilayer forms
the hydrophobic core created when a phospholipid bilayer forms acts as a what to what
- barrier
- to water-soluble molecules
the hydrophilic phosphate heads form what bonds with water
hydrogen
the hydrophilic phosphate heads form H-bonds with water allowing the cell membrane to be used to
compartmentalise
the hydrophilic phosphate heads form H-bonds with water allowing the cell membrane to be used to compartmentalise, this enables the cells to organise what into organelles helping with what
- specific roles into organelles
- helping with efficiency
- (this enables the cells to organise specific roles into organelles helping with efficiency)
composition of phospholipids contributes to the what of the cell membrane
fluidity
if there are mainly saturated fatty acid tails then the membrane will be
less fluid
if there are mainly unsaturated fatty acid tails then the membrane will be
more fluid
phospholipids control membrane protein
orientation
phospholipids control membrane protein orientation, as weak hydrophobic interactions between the phospholipids and membrane proteins do what
- hold the proteins within the membrane - but still allow movement within the layer
what hydrophobic interactions between the phospholipids and membrane proteins hold the proteins within the membrane but still allow movement within the layer
weak
number of fatty acid tails in a phospholipid
2
number of fatty acid tails in a triglyceride
3
what part of a phospholipid is polar
phosphate head
what part of a phospholipid is non polar
fatty acid tails
is a triglyceride polar or non polar
non polar
number of water molecules released during the formation of a phospholipid and triglyceride
3
overall function of a phospholipid is
to be a cell membrane component
overall function of a tricglyceride is
for energy storage
triglycerides are a form of
lipid
triglycerides are made up of
- one molecule of glycerol
- with three fatty acids attached to it
fatty acids in a triglyceride have long what tails
hydrocarbon
fatty acids occur in what two forms
- saturated
- unsaturated
the difference between these saturated and unsaturated fatty acid types is found in their
hydrocarbon tails
in saturated fatty acids, the bonds between the carbon atoms in the hydrocarbon tail are all
single bonds
the fatty acid is said to be what with hydrogen
- saturated
- this means that each carbon atom in the hydrocarbon tail (except for the final carbon atom) is bonded to two hydrogen atoms
an example of a saturated fatty acid diagram
in unsaturated fatty acids there is at least one
carbon-carbon double bond
these double bonds cause the hydrocarbon tail of unsaturated fatty acids to
- kink
- not as straight as saturated fatty acids
the fatty acid is said to be
unsaturated
the fatty acid is said to be ‘unsaturated’ because the hydrocarbon tail does not contain the maximum number of
- hydrogen atoms possible
- this is because each carbon atom in a carbon-carbon double bond can only bond to one hydrogen atom (instead of two)
an example of an unsaturated fatty acid diagram
triglycerides are mainly used as
energy storage molecules
triglycerides are mainly used as energy storage molecules, this is because the long 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
triglycerides are also suitable as energy storage molecules because they are what so
- insoluble
- dont affect the water potential inside the cell
inside cells, triglycerides form
- insoluble droplets
- hydrophobic (water-repelling) fatty acids on the inside
- glycerol molecules on the outside
triglyceride insoluble droplets inside cells diagram
triglycerides are suitable as energy storage molecules as they form insoluble droplets inside cells
phospholipids are another kind of
lipid
in phospholipids, one of the three fatty acid molecules attached to glycerol is replaced by a
phosphate group
this phosphate group is in a phospholipid is
hydrophilic
this phosphate group is hydrophilic (water-loving), whereas the two fatty acids are
hydrophobic (like in triglycerides)
in phosholipids the hydrophilic phosphate head and hyprophpbic fatty acid tails makes phospholipids suitable for making up the
- bilayer of cell membranes
- with the fatty acids facing inwards and the phosphate groups facing outwards
this is also useful as it means the centre of the phospholipid bilayer is
hydrophobic
this is also useful as it means the centre of the phospholipid bilayer is hydrophobic, meaning
water-soluble substances cannot easily pass through
this allows the cell membrane of a phospholipid to act as a
- barrier
- controlling what substances enter and leave the cell
phospholipids bilayer diagram
phospholipids are suitable for making up cell membranes as they form a bilayer
