Required Practicals Flashcards
1
Q
During RP3, why are the potatoes’ skin removed (1 mark)
A
- Different parts of the potato have different thicknesses of skin
- So this would affect the diffusion distance
2
Q
During RP3, why are the potato chips dried with a paper towel before weighing again (2 mark)
A
- To remove any excess liquid on the surface of the potato chips which may add to the mass
- The amount of water on the surface of each chip will vary
3
Q
State the independent variable in RP3 (1 mark)
A
Sucrose concentration
4
Q
State the dependent variable in RP3 (1 mark)
A
% change in mass
5
Q
State the control variables in RP3 (5 marks)
A
- Volume of solution
- Length and diameter of potato chip
- Time left in solution
- Temperature
- Type of potato
6
Q
Why should the potato chips not be squeezed after removing them from the sucrose solutions (3 marks)
A
- Squeezing would damage the cells and cause the cell membranes to break
- So water from inside the cells would come out
- This would give an inaccurate result
7
Q
State 3 aseptic techniques which must be used when doing RP6 (6 marks)
A
- Open lid of Petri dish as little as possible
- To prevent microorganisms from escaping and contaminating the air
- Use a sterile pipette / flame the loop
- To maintain a pure culture of bacteria
- Wash hands with soap
- To prevent contamination of bacteria on hands
8
Q
Why should the neck of the microorganism bottle be flamed (1 mark)
A
- To kill any other microorganisms that may contaminate the agar plate
- If they weren’t killed, they would compete with the microorganism being investigated for the nutrients and oxygen
9
Q
Why must the agar plates be incubated at 25 degrees in RP6 (1 mark)
A
- To prevent the excessive growth of bacteria and potential pathogens from growing
