Core Practicals Flashcards
What variables need to be controlled in the daphnia experiment
Temperature Volume of solutions Stress of daphnia Size of daphnia Time of acclimatisation
Describe the method of the daphnia experiment
Remove daphnia and placing on a cavity slide. Remove pond water and replace with distilled water. Leave for five minutes to acclimatise then observe and count heart rate under a microscope for 30 seconds multiply that number by 2 to get beats per minute. Repeat. Then repeat again with different caffeine concentrations
Give some potential issues with the daphnia experiment
If left too long under microscope= temp could increase (due to the lamp) which could increase the heart rate
Counting of heart beat can be inaccurate
Too high concentration of caffeine kills daphnia
Ensuring Daphnia were same size
What were the Independent and dependent variables for measuring the content of vitamin C in fruit juice
Independent: fruit juice
Dependent: volume of juice required to decolourise DCPIP
What variables will need to be controlled in the vitamin C experiment
Temperature
Concentration of DCPIP solution
Same end point colour
Describe the method of the vitamin C experiment
Pipette 1 cm³ of DCPIP into test tube
Add 1% vitamin C solution drop by drop
Shake the tube gently after each drop
Continue until the blue colour disappears
Record the volume of solution needed to decolourise the DCPIP
Do repeats and calculate the mean
Repeat message with different fruit juices
What issues are associated with the vitamin C experiment
Difficulty in controlling temperature
Amount of shaking (too much adds oxygen which will slightly restore the DCPIP to blue)
Endpoint difficult to judge especially in highly coloured juices
Accuracy of measuring equipment
In an experiment that investigates the effect of temperature on cell membranes what are the Independent and dependent variables
Independent: temperature of water
Dependent: percentage transmission of light through resulting solution
What Control variables are there in the effect of temperature on cell membrane experiment?
Volume of distilled water
Time left in water
Size of beetroot piece
What is the method of the effect of temperature on cell membrane experiment
Using a cork borer and Knife cut pieces of beetroot into 1 cm cylinders
Place in distilled water overnight to remove any dye released on preparation
Wash and blot dry
Place eight boiling tubes of distilled water into eight water baths of different temperatures
Once at the correct temperature add a piece of beetroot into the test tubes
Leave for half an hour
Remove beetroot and shake to disperse dye
Set colorimeter to absorbance on blue/green filter
Calibrate using distilled water
Add beetroot solution to cuvette
Read percentage absorbance
Repeat
What would be the expected result of the effect of temperature on cell membranes
At temperature increased absorbance would increase
Due to the membrane molecules gaining more heat energy vibrating more, to a point where the vibrations caused larger gaps in the membrane enabling the release of dye and
Proteins in the membrane denature leaving large gaps
What issues are associated with the experiment that investigates the effect of temperature on cell membranes
Some beetroot may have skin affecting surface area
Accurate reading of the colorimeter
Colorimeter not properly zeroed or calibrated
Accurate size of beetroots
The beetroot is washed after
The beetroot is from different parts of the root
Ensuring same amount of time at the different temperatures
For the experiment that investigates the effect of changing enzyme conc on rate of reaction, what are the Independent and dependent variables
Independent: concentration of enzyme dependent: time taken for enzyme to breakdown substrate
State the control variables in the experiment that investigates the effect of changing enzyme concentration on the rate of reaction
Temperature volume of enzyme volume of substrate concentration of substrate PH
Describe the method used In the experiment that investigates the effect of changing enzyme concentration on the rate of reaction
Make up different concentrations of enzyme using distilled water
Use a different syringe for each enzyme concentration (To prevent cross contamination)
Set up a water bath for temperature to be kept constant
Place one test tube of 5 cm² casein solution into water bath alongside second test tube containing 2 cm³ of 0.2% trypsin
Allowed to acclimatise for three minutes until the temperature is the same.draw an X on other side of five soon as you see it= transparency
then add trypsin to Caesin start stop clock
Time how long it takes for Caesin solution to turn transparent
Repeat
Then repeat again for next concentration
What issues are associated with the enzyme experiment
Maintaining constant temperature
Accurate making up of the different concentrations
Identifying and point consistently
What other method could be used to investigate the effect of enzyme concentration on rate of reaction
Using catalase in yeast and hydrogen peroxide
Add peroxide to yeast attach gas syringe read off volume of oxygen gas produced every 10 minutes until three readings are all the same, repeat three times for each concentration of yeast solution
What are the Independent and dependent variables for the daphnia experiment
Independent: Caffeine concentration
Dependent: heart rate of daphnia
