Required PRACTICALS Flashcards
Describe practical to investigate Co2 production from seeds
-Soak dried beans in water for about a day so they germinate
-Boil a second batch of beans, so they are killed and can’t respire (control)
-Add hydrogen carbonate into both tubes
-Place a platform made of gauze into each test tube and place beans on there
-Seal tubes with rubber ring
-Leave for an hour
-Tube with germinating seeds, the hydrogen carbonate indicator should be yellow as there’s CO2
Investigate food samples for the presence of Starch:
-Add 5cm3 of sample into test tube
-add few drops of iodine solution and shake
-Colour change from orange to blue black
Food test for glucose:
Benedict’s Test
-Add 5cm3 of food sample to test tube
-Add 10 drops of benedict’s solution
-Leave sample in water bath for 5 mins at 75C
-Colour change from blue to green/yellow if low conc
-Colour change from blue to brick-red if high conc
Food test for proteins
Biuret test:
-Add 2cm3 of food sample into a test tube
-Add 2cm3 of biuret solution and mix by shaking gently
-Colour change from blue to pink or purple
Test for Lipids
Emulsion test:
-Place 1cm3 of food sample in test tube
-Add 2cm3 of ethanol into the tube, cover end of tube and shake
-Allow contents to settle.
-A milky-white emulsion forms
How temperature affects enzyme activity
-Use a pipette to add hydrogen peroxide to a boiling tube
-Put the tube in a water bath at 10C
-Add a potato (catalase source) into boiling tube and attach the bung
-Record the amount of oxygen produced within the measuring cylinder connected to the boiling tube in the first minute
-Repeat at 20,30,40 C 3 times and get mean average
How enzyme activity can be affected by changes in pH
Same as the temperature practical but keep the same temperature and use a buffer solution with different pHs
Diffusion in non-living systems
-Make agar jelly with phenolphthalein and dilute sodium hydroxide.
-Put some dilute hydrochloric acid in a beaker and put cubes of jelly in there
-The cubes turn from pink to colourless as the acid diffuses into the agar jelly.
Osmosis in living systems
-Cut up potato into cylinders and place in beakers with different sugar solutions, one being pure water.
-Measure the length of potato before and after
-They should have shrunk as water has been drawn out of the potato by osmosis.
Osmosis in non-living systems
-Place a visking tube over the end of a thistle funnel, then pour sugar solution down it.
-Put the thistle funnel in a beaker of pure water and measure where the sugar solution comes up to on the glass tube
-Leave overnight, water should’ve moved out of the visking tube causing the solution up the glass tube.
Factors affecting photosynthesis
Co2 concentration, light intensity and temperature.
Effect of exercise on breathing rate
-Sit still for five minutes, then for one minute count the number of breaths made
-Now do four minutes of exercise and count breaths for one minute straight after
-Repeat and work out mean average for both resting and after exercise
-Use other people in investigation also
Investigate the release of CO2 in your breath
-Set up two boiling tubes and add the same amount of limewater to both
-Put your mouth around mouthpiece and breathe in and out several times
-As you breathe in air from room is drawn in through boiling tube A, so that tube stays colourless
-Tube B turns cloudy
