Carbohydrates, Lipids & Water Flashcards
what are organic molecules? (2)
molecules with carbon-carbon and carbon-hydrogen bonds
they’re typically found in living organisms
define monomers
small, repeating units from which larger molecules called polymers are made
define polymers
molecules made from a large number of monomers (3 or more) joined together
how are monomers joined together to create polymers? (3)
a condensation reaction
- joins two molecules (“monomers”) together with the formation of a chemical bond
- involves the removal of a water molecule
how can monomers be split again? (3)
a hydrolysis reaction
- breaks a chemical bond between two molecules (“monomers”)
- involves the use of a water molecule
what are carbohydrates?
a diverse group of organic molecules that range from simple monosaccharides to complex monosaccharides
what are monosaccharides?
examples: (3)
the monomers from which all large carbohydrates are made
- glucose
- galactose
- fructose
how can monosaccharides be joined together? (2)
a condensation reaction
- joins two together through the formation of a glycosidic bond
two monosaccharides = DISACCHARIDE
three monosaccharides = POLYSACCHARIDE
name three disaccharides
- maltose
- lactose
- sucrose
name three polysaccharides
- starch
- glycogen
- cellulose
(alpha) glucose + (alpha) glucose =
maltose
(alpha) glucose + galactose =
lactose
(alpha) glucose + fructose =
sucrose
what are polysaccharides? (3)
a polymer made from joining many monosaccharides together via condensation reactions
- large molecules that don’t pass the cell membrane
- insoluble in water, so doesn’t affect water osmosis
structure and function of: STARCH (4)
storage molecule in plants
made from alpha glucose
branched ; alpha (1-4) glycosidic bonds and alpha (1-6) glycosidic bonds
- more ends available to be broken off for energy
helical ; more compact
- more glucose can be stored in less space
structure and function of: glycogen (6)
storage molecule in animals
polymer of alpha glucose
branched ; alpha (1-4) glycosidic bonds and alpha (1-6) glycosidic bonds
helical ; more compact
- more glucose can be stored in one place
insoluble
large molecule ; can’t diffuse out of cells
what are the differences between starch and glycogen? (3)
animals have a higher metabolic demand than plants (they respire more)
so glycogen, compared to starch, has:
#1: shorter chains
#2: a higher amount of branches
#3: larger surface area
structure and function of: cellulose (6)
structural molecule in plants
polymer of beta glucose
long, straight chains ; beta (1-4) glycosidic bonds
chains can be joined together by weak hydrogen bonds, which become strong when there’s lots of them
this forms microfibrils
- which can then be further wound together to make cellulose fibres
- provide rigidity and strength
what are lipids? (5)
a varied group of molecules that share the following features:
- contain carbon, hydrogen, oxygen
- proportion of hydrogen to oxygen is less than carbohydrates
- insoluble in water
- soluble in organic solvents like alcohol and acetone
what is the main role of lipids?
they’re the main component of the cell surface membrane and membrane-bound organelles
what are the remaining four roles of lipids? (4)
SOURCE OF ENERGY
- provide twice as much energy as the same mass of carbohydrates when they’re oxidised
INSULATION
- when stored under the skin, it helps animals retain body heat
- electrical insulators; make up the myelin sheath
PROTECTION
- the heart and the kidneys have a layer of fat to protect them
WATERPROOFING
what are the two groups of lipids?
- triglycerides
- phospholipids
TRIGLYCERIDES: structure (2)
made from one glycerol and three fatty acid molecules
- joined together via 3 condensation reactions to form ester bonds between the carboxyl group in fatty acids and the hydroxyl group in glycerol
TRIGLYCERIDES: features (4)
- hydrophobic (repel water)
- contain a lot of energy due to the high ratio of C-H bonds compared to C-C bonds
- low energy : mass ratio ; makes them good for storage ; can be stored in a small space
- contain a high ratio of H:O ; release water when oxidised and so can be a good water source for desert animals
FATTY ACIDS: structure (3)
hydrocarbon chain ; they either make for a saturated fatty acid or an unsaturated fatty acid
- saturated have no double bonds between the carbon atoms within the hydrocarbon chain
- unsaturated have double bonds between the carbon atoms
PHOSPHOLIPIDS: structure (3)
- similar to triglycerides, however there is a phosphate group that replaces one of the fatty acids
- the glycerol combines with two fatty acids and one phosphate group
- there are only 2 ester bonds within a singular phosphate molecule
what are the two parts of a phospholipid?
hydrophilic phosphate head
- attracted to water; interacts with it
- the attraction is caused by the polar nature of the phosphate group
hydrophobic fatty acid tails
- repelled by water; faces away from it
- because fatty acids are non-polar
why is water fundamental to life on earth?
the earliest forms of life are thought to have evolved in water
what are the five properties of water? (5)
- it’s a metabolite
- it’s a solvent
- it has a large specific heat capacity
- it has a large latent heat of vaporisation
- cohesion
water as a… metabolite
allows water to be involved in metabolic reactions such as condensation and hydrolysis
water as a… solvent (2)
- allows metabolic reactions to occur
- allows the transportation of substances
water as having a… high specific heat capacity (2)
- ‘buffers’ changes in temperature
- helps mammals to maintain a core temperature despite changes in environmental temperature
water as having a… large latent heat of vaporisation (2)
- provides a cooling effect
- requires a lot of energy to evaporate water and so when evaporation occurs, it takes away this energy from the body which provides the cooling effect.
water as being… cohesive (2)
- supports the formation of continuous molecules of water
- provides surface tension which supports small organisms on the surface of water
can triglycerides be classed as polymers?
no because they are not made from monomers with the same or similar structure
draw out an alpha glucose molecule
list the three different tests for a carbohydrate
- benedict’s test for reducing sugar
- benedict’s test for non-reducing sugar
- iodine test for starch
describe the benedict’s test for a reducing sugar (2)
- add equal volumes of benedict’s solution and sample to a test tube
- heat to 95 degrees
what is the result of the benedict’s test if a reducing sugar is present?
formation of a brick red precipitate
why is the benedict’s test known as “semi-quantitative”?
because the colour of the precipitate indicates an approximate concentration
describe the benedict’s test for a non-reducing sugar (3)
- boil a sample with hydrochloric acid for 5 minutes
- neutralise the solution by adding an alkali
- now test as you would for a reducing sugar
describe the step by step method for making a calibration curve to estimate the unknown concentration of a reducing sugar (6)
- make up several known concentrations of a reducing sugar
- carry out the benedict’s test on each of these concentrations
- use a colorimeter to measure the absorbance
- plot calibration curve
- carry out benedict’s test on the sample with an unknown concentration
- then measure its absorbance via the colorimeter
