RP 7-12

Question 1

What is the main aim of RP 8?

Answer 1

Determining factors that affect the dehydrogenase activity in chloroplasts

Question 2

What are the control variables in RP8?

Answer 2

Source of chloroplasts, volume of the chloroplasts suspension, volume of DCPIP, concentration of DCPIP

Question 3

Explain the colour change from blue to green in RP8?

Answer 3

The DCPIP in the solution will be reduced as it accepts electrons released from the chlorophyll that have been transferred along the electron transport chain

Question 4

Explain why the DCPIP remains blue in the tube which is covered in foil in RP8

Answer 4

The foil prevented light from reaching the chlorophyll, so photoionisation did not take place and no electrons were released from the chlorophyll molecule. This meant no electrons were available to reduce DCPIP, so it remains blue

Question 5

Explain why an isolation medium which was ice cold is used in RP8

Answer 5

Blending the leaves releases the enzymes from the cell which could damage the chloroplast. An ice-cold buffer will reduce the rate of enzyme activity and prevent chloroplast damage

Question 6

Explain why sucrose solution is included in the isolation medium in rp8?

Answer 6

The presence of sucrose reduced the water potential of the isolated medium. This means that there is no net movement of water into the chloroplasts. If water entered the chloroplasts by osmosis, they would burst

Question 7

Explain why DCPIP in a tube with boiling suspension would not decolourise the solution in rp8

Answer 7

Boiling would denature the proteins in the chloroplasts, including those that make up the electron transfer chain. Electrons would not pass along the electron transfer chain and so cannot be accepted by DCPIP

Question 8

Explain the advantage of using different concentrations of chemicals for weed killers

Answer 8

A chemical could be used to compare different concentrations of chemicals to be compared as weed killers

Question 9

Explain why it is important that these water potentials were the same

Answer 9

So osmosis doesn’t occur and the organelles do not burst in the cell

Question 10

What is the aim of RP9

Answer 10

Factors affecting the rate of respiration in single-celled organisms

Question 11

What are the two ways that the rate of respiration can be determined in RP9?

Answer 11

• Respirometer
• Using a dye that changes colour when reduced - methylene blue

Question 12

What variables should be controlled in RP9?

Answer 12

• Volume of the dependent variable (volume of culture of single-celled organisms)
• Volume of glucose solution
• Volume of methylene blue

Question 13

Explain why in a respirometer that the coloured liquid moves towards the left in RP9

Answer 13

It will take in oxygen and release it in respiration. The carbon dioxide is absorbed by sodium hydroxide and so the volume of gas in the tube which decreases the pressure. This causes the liquid to move down the pressure gradient towards the left

Question 14

How does temperature impact the rate of respiration?

Answer 14

At higher temperatures, enzymes have more kinetic energy which means that they can increase the number of successful collisions leading to an increase in the rate of respiration

Question 15

Give two measurements the student will have to make to determine the rate of aerobic respiration of these seeds

Answer 15

• The movement of the coloured liquid in the tube
• The diameter of the tube

Question 16

Give the change the student needs to make to the contents of the apparatus and describe how he could calculate the volume of carbon dioxide produced

Answer 16

Replace the potassium hydroxide with water then record the distance moved without the potassium hydroxide. Then use the difference in calculate volumes to calculate the volume of carbon dioxide produced

Question 17

What is the aim of RP10?

Answer 17

The effect of an environment variable on animal environment

Question 18

What are the control variables in RP10?

Answer 18

The number of maggots being used, where the maggots are obtained from, how long they are left in the choice chamber etc

Question 19

Suggest why the student put a damp filter in each half of the choice chamber RP10

Answer 19

The damp conditions provide a more favourable environment for maggots as this prevents them from drying out

Question 20

Suggest why the student used a plastic spoon to pick up the maggots and not a pair of forceps

Answer 20

A student may squeeze too hard which could harm the maggots

Question 21

Why are maggots recorded in dark conditions than light considered more favourable?

Answer 21

If the maggots move towards the dark regions, they are less likely to been seen by predators and this increases their chance of survival

Question 22

State a null hypothesis for RP10

Answer 22

There is no significant difference in the number of maggots found in the light and dark conditions

Question 23

What stats test should be used in rp10 and why?

Answer 23

Chi squared and because the data is categoric and she is comparing frequencies

Question 24

What is the aim for rp11?

Answer 24

Use a calibration curve to identify an unknown concentration

Question 25

What are the control variables in RP11?

Answer 25

Volume of each test sample, volume of benedict’s solution, temperature of the water bath, time in the water bath

Question 26

How a student could determine if the pink colour had completely disappeared in RP11

Answer 26

Use a solution that had already been decolourised and then compare all the other solutions with it

Question 27

Why a student may repeat their results in rp11?

Answer 27

This is so that the student can ensure their measurements are repeatable and could identify anomalous results

Question 28

Explain how a student may modify the method to find a more accurate concentration of the unknown solution?

Answer 28

The student may repeat their experiment by using more concentrations between the concentrations that they have already used

Question 29

What is the aim of RP12?

Answer 29

The effect of an environmental factor on specie distribution

Question 30

What are the control variables in rp12?

Answer 30

Abiotic and biotic factor examples, The quadrat being used, the time of day it is being used, the distance each time, how the random areas are being determined

Question 31

Suggest one reason why the student measured the leaves while the were still attached to the plant in rp12?

Answer 31

Picking the leaves may damage the plant. The leaves may also dry out and shrink once they have been picked, which would reduce their size

Question 32

Determine the graph that the student should have plotted. Give a reason for your answer?

Answer 32

She should draw a scatter graph because she is looking for a relationship between two continuous variables

Question 33

What is the aim of required practical 7?

Answer 33

Using chromatography to investigate leaf pigments

Question 34

What factors affect the rate that the pigments move up the chromatography paper?

Answer 34

• The solubility of the pigments
• The size of the pigments
• Their tendency to adhere to the chromatography paper

Question 35

How to calculate the Rf value?

Answer 35

Distance from the origin to the centre of the pigment spot/distance from the origin to the solvent front

Question 36

Explain why the student used pencil to draw the spotting line and not the pen

Answer 36

Ink mixes with the solvent and distorts the chromatograph. This because ink is soluble and so it will seperate in the chromatogram

Question 37

Explain why the solvent has to be below the origin line?

Answer 37

The pigments are soluble in the solvent and so would be removed from the paper if the solvent was above the origin line

Question 38

Explain why the students did not move the boiling tubes?

Answer 38

This might cause the solvent to travel up the paper at an angle instead of running straight

Question 39

Describe the method the student used to separate the pigments after the solution of pigments had been applied to the origin

Answer 39

• Ensure that the level of solvent is below the origin line
• Remove the solvent before it reaches the top