biological molecules Flashcards
what is the test for reducing sugars?
-add Benedict’s solution (which is blue in colour) to sample
-heat the test tube with the solution in a water bath fora few minutes
-a coloured precipitate will form, it will be brick-red if there’s a high concentration of reducing sugar
what is the test for non-reducing sugars?
-add dilute hydrochloric acid to sample
-heat test tube with sample in water bath for a few minutes
-neutralise the solution by adding sodium hydrogen carbonate
-add Benedict’s solution and put sample in water bath again for a few minutes
- if solution turns brick-red non-reducing sugars are present in high concentrations
starch function and uses
-storage polysaccharides in plants
-made from amylose and amylopectin
-amylose: unbranched helix shaped chain with 1,4 glycosidic bonds between α-glucose molecules
-amylose: the helix shape enables it to be more compact and thus it is more resistant to digestion
-amylopectin: 1,4 glycosidic bonds between α-glucose molecules but also 1,6 glycosidic bonds form between glucose molecules creating a branched molecule
-amylopectin: the branches result in many terminal glucose molecules that can be easily hydrolysed for use during cellular respiration or added to for storage
glycogen function and uses
-storage polysaccharide in animals and fungi
-glycogen is more branched than amylopectin making it more compact which helps animals store more
-the branching enables more free ends where glucose molecules can either be added or removed allowing for condensation and hydrolysis reactions to occur more rapidly - thus the storage or release of glucose can suit the demands of the cell
cellulose function and uses
-cellulose ia a polysaccharide
-insoluble in water
-is a polymer consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds
-main structural component in cell walls
-the high tensile strength of cellulose allows it to be stretched without breaking which makes it possible for cell walls to withstand turgor pressure
what is the test for lipids?
-add ethanol to the sample
-shake the sample in a test tube
-add water
-if the colour turns milky white or there is a milky white precipitate, lipids are present
what is the test for proteins?
-the buiret test
-add NaOH to the sample
-then add copper sulphate to the sample
-if the sample turns purple, proteins are present
what is the lock and key model?
-enzyme is the lock
-substrate is the key
-the substrate needs to be a specific shape to fit into the ‘lock’ which is the enzyme
what is the induced fit model?
-the substrate binds to the active site of the enzyme
-this forms an enzyme-substrate complex
-and this changes the shape of the active site slightly
how does temperature affect enzyme activity?
-higher temperatures will denature the enzymes active site so no enzyme-substrate complexes can be formed
-this decreases the rate of reaction
-at optimal temperature, more enzyme-substrate complexes can be formed so the rate of reaction is increased
how does pH affect enzyme activity?
-if the pH is too low or too high the enzyme will denature
-this reduces the rate of reaction
-if pH is optimal, more enzyme-substrate complexes can be formed and the rate of reaction will increase
-this graph looks like a bell-shaped curve
how does substrate concentration affect enzyme activity?
-if there is a higher concentration of substrates there will be an increased rate of reaction as more enzyme-substrate complexes can be formed
-this graph plateaus due to all of the active sites being used up
the rate of reactions at different temperatures practical
-set up boiling tubes with some concentration and volume of hydrogen peroxide and add pH buffer to keep pH constant
-put boiling tubes in water baths at different temperatures and another tube with a catalyst
-keep in water bath for 5 minutes
-use pipette to add same volume and concentration of catalyst into each boiling tube
-quickly attach bung and delivery tube
-record how much O2 is produces in 60 seconds
-repeat 3 times and calculate a mean
test for the presence of starch in a solution practical
-put a drop of iodine in potassium iodine in each well of spotting tile
-mix together a known concentration and volume of amylase and starch in a test tube
-use a pipette to put a drop of mixture onto wells at regular intervals
-observe colour change
-blue black= starch present, orange brown= no starch
-repeat using different concentrations of amylase and take a mean
