practicals Flashcards
Investigate how enzyme activity can be affected by changes in temperature.
- Test tube of starch solution is placed in a water bath of set temperature for several minutes (0, 10, 20, 30, 40, 50, 60 degrees)
- Solution of the amylase enzyme is added into the test tube of starch solution
- Immediately after amylase is added into the test tube, a pipette is used to add droplets of mixture into wells
- Immediately, after the mixture is added into wells, a few drops of iodine solution is added
- Process is repeated in increments of fixed time until iodine turns orange, indicating that starch has completely broken down into glucose
- Time taken for starch to be completely broken down is compared to that of each respective temperature (time take for iodine solution to turn orange with each respective temperature)
Result: As temperature increases towards optimum, the rate of amylase activity increases as shown with the decrease in time taken for iodine solution to turn orange.
Investigate how enzyme activity can be affected by changes in pH.
- Test tube of starch solution is placed in a water bath of a set temp (approx 30-40 degrees)
- Solution of amylase enzyme is added into the test tube of starch solution
- Immediately after, buffer solution of set pH is added which will maintain reaction mixture at set pH
- A pipette is used to add droplets of mixture into wells on tile
- A few drops of iodine solution is added
- Process is repeated in increments of fixed time (seconds) until iodine turns orange, indicating that starch has completely broken down into glucose
- Time taken for starch to be completely broken down is compared to that of each respective pH (time taken for iodine solution to turn orange with each respective pH of buffer solution)
Result: As pH increases towards optimum pH, the rate of amylase activity increases as shown with the decrease in time taken for iodine solution to turn orange
Investigate diffusion and osmosis using living and non-living systems.
TO BE LEARNED
Investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll.
- Place pond weed in a beaker of water
- Change the independent variable
- Leave for 5 minutes to allow pond weed to adapt to environment
- Count the number of air bubbles produced in a fixed period of time
- Increase or decrease the independent variable by a fixed increment (e.g. distance of lamp to change light intensity)
- Repeat process to obtain a range of data and analyse results
How to change the independent variable:
Light intensity - Use a lamp and adjust the distance from pond weed
CO2 concentration - Add sodium bicarbonate to increase concentration. To decrease add sodium hydroxide.
Chlorophyll - use variegated plant: green plant containing chlorophyll and white plant without chlorophyll
Investigate the energy content in a food sample.
- Measure a fixed volume of water into a boiling tube
- Use a thermometer to measure the temperature of water
- Use a weighing scale to measure the mass of food sample
- Burn food sample via complete combustion and hold directly underneath the boiling tube to heat the water until it burns out
- Use thermometer to measure the final temperature of water
- Use the equation: energy transferred = (mass of water heated x 4.2 x temp increase) / mass of food
Investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.
- One end of a capillary tube is attached to a flash of sodium hydroxide to allow the inflow of air
- This flask is connected by a capillary tube to a flask of hydrogen carbonate
- This flask is connected by a capillary tube to a flask of respiring organisms (e.g. worms)
- This flask is connected by a capillary tube to a flask of hydrogen carbonate
- Lastly, one end of a capillary tube is attached to this flask to allow the outflow of air
Result: As air enters the first capillary tube, sodium hydroxide will absorb and remove carbon dioxide, therefore causing hydrogen carbonate indicator to turn red. As air (abundant in oxygen) enters the flask of respiring organisms, organisms will respire aerobically to produce CO2 as waste product, therefore causing hydrogen carbonate indicator to turn yellow. This shows the production of CO2 by living organisms, showing the evolution of CO2.
Investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator.
Hydrogen carbonate indicator goes yellow in high concentration of CO2, red in atmospheric concentration and purple in low CO2 concentration.
1. Place pondweed in a beaker of hydrogen carbonate indicator
2. Place light source at a set distance to adjust light intensity
3. Allow plant to adapt to adjusted environment for a few minutes
4. Observe and record the colour of indicator
5. Change light intensity and repeat process
Investigate breathing in humans, including the release of carbon dioxide and the effect of exercise.
Investigating release of CO2 during exercise:
1. Measure a fixed volume of limewater into a boiling tube
2. Use a straw and blow into the solution of limewater
Investigating effect of exercise on breathing:
1. Stationary breathing rate of participants is recorded
2. Specific exercise will be performed by participants at the same intensity for a fixed period of time
3. Breathing rate after exercise is recorded
4. Results are compared
Investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot.
Potometer - device used to measure the volume of water absorbed by the plant
1. Cut shoot underwater to prevent air from entering xylem and place through hole in cork provided with potometer.
2. Fill potometer with water and fit the stopper holding the leafy shoot to apparatus
3. Use vaseline to seal apparatus to ensure equipment is airtight
4. Trap air bubble in capillary tube by dipping end of tube into a beaker of water
5. Measure and record the starting distance of air bubble
6. Change environmental factor being investigated
7. Allow shoot to adapt a new environment for a fixed period of time
8. Measure and record the final distance of air bubble to calculate the total volume of water absorbed by plant
9. Change intensity of environmental factor and repeat process
Investigate the conditions needed for seed germination.
Conditions needed for seed germination: water, oxygen, warmth
1. Cotton wool is placed at the bottom of four boiling tubes, each containing five cress seeds
2. Each test tube is then individually set up:
Tube A - moist cotton wool and placed in a warm environment
Tube B - dry cotton wool and placed in a warm environment
Tube C - moist cotton wool and is placed in a cold environment
Tube D - cotton wool soaked in boiled water that is cooled off and layered with oil on top
3. After a fixed number of days has passed, results are compared via number of cress seeds germinated and height of germinated seed
Investigate the population size of an organism in two different areas using quadrats.
- Place quadrat randomly within sampling area
- Count the number of members of the same species within the quadrat
- Repeat this numerous times within sampling area using the same size quadrat
- Repeat the process in another area to compare results
- Use the equation: population size = (total area/sampled area) x number of organisms
Investigate the distribution of organisms in their habitats and measure biodiversity using quadrat.
- Place quadrat randomly within sampling area
- Count the number of members of the same species within the quadrat
- Repeat this numerous times within sampling area using the same size quadrat
- Repeat the process in another area to compare results
- Additionally, results can be shown on a map of a sampled area, displaying which areas are densely populated by certain species and vice versa
Investigate the role of anaerobic respiration by yeast in different conditions.
- Mix boiling tube of sugar solution with yeast, covering it with a layer of oil to prevent the entry of oxygen; hence, ensuring aerobic respiration
- Boiling tube is connected to a test tube of limewater via capillary tube that is kept airtight by a bung
- Boiling tube of sugar solution with yeast is placed in a water bath of set temperature
- Rate of CO2 production is measured by number of bubbles produced in a fixed time in a test tube of limewater
- Compare results obtained at different temperatures
