3.3 &3.4 testing for carbohydrates Flashcards
whats a condensation reaction
its a reaction which joins monomers by chemical bonds and a water molecule is removed
whats hydrolysis
a water molecule is added to break a chemical bond between two molecules
examples of monomers
nucleotides
amino acids
monossacharides
what is a monomer
a small unit which makes up larger molecules
whats a polymer
molecules made up from monomers joined together
what elements do carbohydrates consist of
carbon
hydrogen
oxygen
what are carbohydrates
long chains of sugar units a called saccharides
what type of bond is found in carbohydrates
glycosidic bonds
what are the three types of saccharides
monosaccharides
disaccharides
polysaccharides
how do monosaccharides join together to make disaccharides and polysaccharides
by glycosidic bonds in condensation reactions
how many carbons does glucose contain
6
what are the two isomers of glucose
alpha glucose and beta glucose
what is the disaccharide maltose made up of
two glucose molecules
what is the disaccharide sucrose made up of
glucose and fructose
what is the disaccharide lactose made up of
glucose and galactose
whats the function of glycogen
its the main energy store in animals
what bonds does glycogen contain and what glucose is it made up of
1,6 and 1,4 glycosidic bonds between alpha glucose
how is glycogen adapted for its function
lots of side branches so glucose can be rapidly hydrolysed to release energy quickly.
and it is a relatively large but compact molecule so can store more glucose
and isn’t water soluble so doesn’t affect water potential
what is the function of starch
to store energy in plants
starch is a mixture of what two polysaccharides
amylopectin and amylose
what bonding is present between what glucose molecules in amylose
1,4 glycosidic bonds between alpha glucose
whats the structure of glycogen like
highly branched molecule
whats the structure of amylose like
unbranched coiled compact molecule
how is amylose adapted for its function
its compact so can store more glucose and isnt water soluble so doesnt affect water potential
what bonding is present between what molecules in amylopectin
1,6 and 1,4 glycosidic bonds in alpha glucose
whats the structure of amylopectin like
a branched molecule
how is amylopectin adapted for its function
its branched so can be rapidly hydrolysed to release glucose
and isnt water soluble so doesnt affect water potential
whats the function of cellulose
it provides structure in plant cells, its a component of cell walls
why can beta molecules join together the same way alpha molecules can
the hydroxyl groups on carbons 1 and 4 are too far apart to react so two beta molecules can only react if one is turned upside down
whats the structure of cellulose like
its straight chains held parallel by hydrogen bonds
what bonds hold what molecules together in cellulose
1,4 glycosidic bonds together beta molecules
when beta molecules are joined via condensation reaction why does it form cellulose not starch
as the alternate beta has to be joined upside down as the hydroxyl gorups on C 1&4 wouldnt be close enough otherwise, when they are joined this way they are unable to coil or form branches so a straight chained molecule is formed
what does cellulose molecules join by hydrogen bonds to form
microfibrils
what do microfibrils join to form
macrofibrils
whats the test for reducing sugars
using benedicts reagent which is alkaline copper (11) sulphate which is added in equal parts to the sample then heated in a water bath
what shows a positive test for reducing sugars
blue to brick red
as the reducing sugar adds electrons and reduces the blue Cu2+ ions to brick red Cu+ ions a brick red precipitate is formed
whats the test for non reducing sugars
they dont react with benedicts so have to be boiled with NaOH first then warmed with benedicts solution as non reducing sugars eg sucrose has to be hydrolysed to reducing sugars eg glucose and sucrose
whats the test for starch
iodine test
a few drops of iodine solution are mixed with potassium iodide solution
whats the positive test for starch
yellow/brown to purple/black
what do reagent strips test for
the presence of reducing sugars commonly glucose
what does a colorimeter do
it quantitively measures the absorbance of light by a colored solution this can be used to determine the concentration of glucose in a solution
what do biosensors do
they determine the presence and concentration of molecules such as glucose
whats the analyte in a biosensor
the compound under investigation
what are the three stages in using a biosensor
molecular recognition (a protein or ssDNA is immobilised to a surface eg glucose test this will interact with or bind to compound under investigstion)
transduction (the interaction in the molecular recognition stage will cause a change in a transducer which detects the change and produces a response eg relseasing dye on test strip)
display (this procuces a visable signal eg colour on test strip)
