Biology - key mock practicals Flashcards
Evidence of photosynthesis - testing for starch
Why is the leaf boiled in water for 1 minute at the start?
To break apart the leaf cells
Evidence of photosynthesis - testing for starch
Why is the leaf heated in ethanol?
To dissolve and remove the chlorophyll
Evidence of photosynthesis - testing for starch
What colour will iodine turn if starch is present?
Blue/black
Evidence of photosynthesis - testing for starch
Why is the plant kept in a cupboard before starting the experiment?
No prevent photosynthesis and ensure that there is o starch present at the beginning of the experiment
Gas exchange in plants
What colour is the hydrogencarbonate indicator in atmospheric air?
Red
Gas exchange in plants
What colour is the hydrogencarbonate indicator in air with more CO2?
Yellow
Gas exchange in plants
What colour is the hydrogencarbonate indicator in air with less CO2?
Purple
Gas exchange in plants
Why does the hydrogencarbonate indicator turn yellow in the test tube covered in foil?
There is more CO2 present as it isn’t being used up in photosynthesis
Gas exchange in plants
Why does the hydrogencarbonate indicator turn purple in the test tube which is under light?
There is less CO2 present as it is being used up in photosynthesis
What is a control experiment?
An experiment without any factors, normal conditions
Gas exchange in plants
What would the control variable be?
A test tube without a leaf
Evidence of photosynthesis - varying environmental conditions
Why is the pondweed kept in a large beaker of water?
To absorb the heat from the lamp and prevent the leaf from changing temperature
Evidence of photosynthesis - varying environmental conditions
What two ways could the rate of photosynthesis be measured?
Counting the number of bubbles produced in a certain time
Analyzing the volume of oxygen produced
Evidence for respiration - peas in flasks
What will happen to the temperatures in flasks A and B, and why?
Flask A will experience an increase in temperature as the living peas inside will produce heat while respiring
Evidence for respiration - peas in flasks
Why are the peas soaked in milton solution?
To kill off bacteria to prevent them from affecting the results
Evidence for respiration - peas in flasks
How could you show that only flask A produces CO2?
Bubble the gases give off through limewater, flask A;s will go cloudy
Why are control experiments used?
To show the organism is causing the change to the variable being measured
Testing for biological molecules
What colour will iodine turn if starch is present?
Blue/black
Testing for biological molecules
Why is a Bunsen burner needed to test for sugars?
The substance needs to be heated to around 85 degrees C
Testing for biological molecules
What colour does Benedict’s solution turn when sugar is present?
Brick red
Testing for biological molecules
What is the colour change which occurs when testing for proteins?
Blue to purple
Investigating factors affecting respiration with yeast
What variables might affect the rate of respiration?
Concentration of oxygen, mass of available glucose, temperature or pH
Investigating factors affecting respiration with yeast
How is the rate of respiration measured?
Time for limewater to go cloudy
Investigating factors affecting respiration with yeast
Why is there a thin layer of oil present?
To prevent more oxygen from reaching the solution, and to ensure the yeast respires anaerobically
