Required Practicals Paper 1 Flashcards
use qualitative reagents to test for a range of carbohydrates, lipids, and proteins
to test for sugars e.g. glucose add benedicts reagent and heat in a water bath for two minutes. if sugar is present it will turn red
to test for starch add iodine solution. if starch is present, it will turn blue-black
to test for protein add a biuret reagent. if protein is present, it will turn purple
use qualitative reagents to test for a range of carbohydrates, lipids, and proteins: considerations, mistakes, and errors
do not boil the mixture for a long time, because any starch present might break down sugars and test positive
refer to iodine solution, not iodine
sometimes the purple colour is difficult to see. try holding the test tube in front of a sheet of white paper.
investigate the effect of PH on the rate of reaction of amylase enzyme
put a test tube containing starch solution and a test tube containing amalyse into a water bath at 37 degrees celsius
after 5 minutes add the amalyse solution to the starch
every 30 seconds take a drop from the mixture and test it for starch using an iodine solution
record how long it takes for the starch to be completely digested
repeat the experiment at different PH values using different buffer solutions
investigate the effect of PH on the rate of reaction of amalase enzyme: Variables
the independent variable is the PH because it is deliberately changed
the time taken for the starch to be digested is the dependant variable because it is measured
temperature, concentration and volume starch, and amalyse are the control variables as they are kept the same
rate of reaction of amalase enzyme Practical: considerations, mistakes, and errors
the solutions need to be left in the water bath for a while to reach the correct temperature before they can be mixed
after mixing, the tube must be kept in a water bath
a buffer solution must be used to keep the reaction mixture at a certain fixed PH
Amalase enzyme practical: Hazards and risks
care must be taken if a bunsen burner is used to heat the water bath
take care not to spill iodine solution on the skin
pondweed required Practical
place a piece of pondweed in a beaker and shine a light at it using a lamp a specific distance away
record the number of bubbles of gas coming out of the pondweed in one minute
repeated this with the lamp at different differences from the pondweed
pondweed practical variables
the independent variable is the light intensity
the dependant variable is the number of bubbles in one minute
the control variable is the pieces of pondweed, the temperature, and the concentration of carbon dioxide
pondweed practical: considerations, mistakes, and errors
it is best to take at least two readings at each distance and calculate the mean of the number of bubbles
carbon dioxide is provided by adding a small amount of sodium hydrogen carbonate to the water
pondweed practical Hazards and Risks
Care must be taken to avoid any water being dropped onto the hot light bulb
