Practicals Flashcards
Practical: investigate how enzyme activity can be affected by changes in temperature
- The enzyme amylase breaks down starch into maltose and if starch is present, iodine will turn from browny orange to blue-black
- Heat a solution containing starch to a set temp, such as 30°C
- Prepare a spotting tile by adding a couple of drops of iodine to each well
- Once it’s reached the correct temp, add the enzyme amylase (atp the amylase will start digesting the starch); start timer straight away
- After one minute on the timer, add a sample of the solution into a tile, it should be blue-black
- Every minute, transfer a droplet of the solution into a new tile with iodine in it until the solution stops turning blue-black; this means the amylase has broken down all the starch
- Record time taken for reaction to be completed and repeat these steps at different temperatures
practical: investigate diffusion and osmosis using living and non-living systems
Investigating Osmosis
C - we are changing the concentration of sucrose solution.
O - The potato cylinders will all be taken from the same potato/potatoes of the same age
R - We will repeat the investigation several times to ensure our results are reliable
M - We’ll measure the change in mass of potato cylinders
M2 - Over four hours
S - We will control the volume of secret solution used, the dimensions of the potato cylinders
Investigate effect of temp on diffusion
C - Changing the temperature in the environment
O - Beetroot cubes will all be taken from the same beetroot / beetroot of same age
R - We’ll repeat the investigation several times to ensure our results are reliable
M - We’re measuring the colour change of the liquid
M2 - After 10 minutes
S - We’ll control the volume of water used & the dimensions of each beetroot cube
Photosynthesis: Testing leaf for starch
- Boil the leaf to break down cell walls
- Pleace the leaf in hot ethanol to remove chlorophyll
- Rinse leaf in cold water to soften it and add iodine solution; if starch is present, leaf will turn blue-black
Photosynthesis: Chlorophyll test
- Cover part of a leaf with aluminium foil and place in sunlight (exposed part of leaf will photosynthesise and store starch)
- After performing a starch test, we’ll see that
- Exposed part of leaf will turn blue-black
- Part that was covered will remain orange-brown
- This is because the foil blocked out the light required for photosynthesis therefore no glucose was produced which could be converted to starch
Photosynthesis: Oxygen Production
- Place lamp measured distance away from apparatus
- Place pondweed in a flask and add sodium hydrocarbonate o the water to make sure the plant has enough CO2
- Place a test tube over the flask to collect the oxygen
- Dependant: Number of oxygen bubbles released per minute
- Independant: Distance of lamp from pondweed
practical: investigate the energy content in a food sample
- Add water to clamped boiling tube
- Record initial temp of water
- Add food sample on mountain needle and ignite using bunsen burner
- Hold burning food sample under boiling tube of water until completely burned
- Record final temp of water using thermometer
- Find out the amount of energy released using formula
energy released = mass of water x change in temp of water x 4.2
practical: investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms
Put hydrogencarbonate solution into a test tube, then place a gauze into the test tube and place beans onto it. Seal the test tube with rubber bung. You will see that the solution will turn from red to yellow when CO2 is present
practical: investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
- Add same number of hydrogen carbonate indicator into 4 boiling tubes
- In 3 tubes, place similar sized and healthy leaves and add rubber bung to trap the leaf
- Completely wrap one with aluminium foil and another with a gauze
- Place all four in bright light and leave for one hour
- You’ll see that in the control tube (nothing added), there won’t be any changes, still orange
- In the tube covered in aluminium, the indicator will be yellow because there is no photosynthesis occuring and only respiration
- In the shaded tube the indicator will be a similar orange colour because it experiences some photosynthesis and respiration
- The indicator in the well lit tube will become purple because there’ll be some respiration but LOTS of photosynthesis which will lower CO2 conc. in the tube
practical: measuring transpiration
- submerge potometer underwater and cut plant shoot underwater to prevent air from entering xylem + make sure its airtight
- dry leaves of shoot, then allow single air bubble to form in capillary tube
- record starting position of air bubble, leave for 30 mins then record end position of air bubble
- keep conditions constant during experiment; temperature, air humidity, supply of water to plant
