RP 1-6 Flashcards
What is the aim of RP1?
Factor affecting the rate if enzyme controlled reactions
What are the control variables in RP1?
Controlling all other factors that don’t include the one you are investigating
- Temperature, pH, Enzyme concentration, substrate concentration, conc of inhibitors
In RP1, a student controlled the temperature. State two other variables that the should have controlled
Concentration of amylase and pH
Describe how the temperature could have been monitored - RP1
The use of a thermometer in a water bath and check the temperature every 10 minutes to make sure it remains constant
The student maintained the temperature at 30 degrees, why may it be faster at 40 degrees - RP1
The starch and amylase have more kinetic energy at higher temperatures so there are more successful collisions and so more E-S complexes will be formed
The student took samples until the blue-black colour no longer appeared. How would the student ensure it remained consistent - RP1
She could have compared the colour of each sample to the colour of the reaction mixture that has gone to completion and been tested with iodine solution
The student concluded that the optimum ph was 5, explain why this may not be valid? - RP1
The student needs to repeat the experiment using smaller intermediary values. This may include pH 4 to pH 6
What is the aim of RP2?
Preparing and observing a root tip squash
How do you calculate the mitotic index?
Number of cells undergoing mitosis/Total number of cells
What are the control variables - RP2
- The same root tip being use
- The same age root tip
- The same length of root tip
How to use a microscope - RP2
- Select the smallest objective lens
- Place your slide on the stage
- Use the coarse focus to either raise the stage or lower the lense
- Look through the eyepiece lens
Adjust with fine focus
How to calibrate the eyepiece graticule?
- Place a stage micrometer on the stage of a microscope
- Align the scales of the eyepiece graticule and determine how many eyepiece graticules go into one stage micrometre
Explain why the student added a drop of stain - RP2
The stain binds to the chromosomes, so the become visible
Explain why the cover slip was pressed down firmly - RP2
To squash the root tip into a thin layer so that the light could pass through the sample
Explain why the student handled the hydrochloric acid with caution - RP2
Highly concentrated which can be highly corrosive
What is the aim of RP3?
Using a calibration curve to estimate the water potential
What are the control variables - RP3?
- Temperature
- Source of the plant tissue
- Size and shape of the plant tissue
- Batch of stock solution
- Length of time the plant tissue is immersed in the solution
Suggest why the student removed the ‘skin’ of the potato? - Rp3
The skin is a different tissue from the rest of the potato and so has a different water potential
Why did the student use potato chips from the same potato? - RP3
If the potato chips are from the same potato, all the cells will have the same water potential
Suggest why the student processed her data to find the percentage change in mass - RP3?
The initial mass of the potato chips was different, so working out the percentage change would allow her to make a valid comparison
Explain how the student could use her processed data to find the water potential - RP3
- Plot a graph with concentration on the x-axis and percentage change in mass on the y-axis
- Find concentration where curve crosses the x-axis / where percentage change is zero
- Use (another) resource to find water potential of sucrose concentration (where curve crosses x-axis)
What is the aim of RP4?
Factors affecting the membrane permeability
What are the control variables in RP4?
- Source of the plant
- Time in the solution
- Size and shape of the plant tissue
What are the 2 measures to determine the permeability of a membrane?
- Producing colour standards
- Colorimeter
Suggest how the increase in temperature of the water caused the release of the red pigment
- Proteins in membrane will denature
- Phospholipid are damaged or melt
Why did the student put the beetroot in distilled water after cutting them? RP4
- This is so that the pigment from the beetroot is released into the distilled water due to the effect of temperature changing the permeability
Why were the test tubes of distilled water left in the water bath for 5 minutes before adding the beetroot - RP4
Allows the water to equilibrate
Why did the student shake the test tubes every 5 minutes? - RP4
- This is to maintain the diffusion gradient for the pigment to pass out of the cells and into the distilled water
Why did the student use fresh beetroot instead of cooked beetroot? - RP4
Cooking would involve the beetroot to be heated to high temperatures that would denature the proteins in the plasma membrane and allow the pigment to leak out
What is the aim for RP5?
Dissection of an organ or system from an animal orplant
What are rules of biological drawing? - RP5
- Use a sharp pencil
- Do not shade or use colour
- Do not sketch
- Label the structures
What are some safety precautions when dissecting an organ?
- Disinfect surfaces before and after
- Wear gloves/apron
- Scalpel should be faced down when carried and not near the edges of the table
Describe how a student could prepare a piece of lower epidermis to observe on an optical microscope?
- Take a clean glass slide and add one drop of water to the centre
- Peel off the lower epidermis which is a thin as it is a single layer of cells
- Place the cover slide at a 45degree angle and gently lower using a mounted needle
What is the aim of RP6?
Using aseptic techniques to investigate the effect of antimicrobials
What are the examples of aseptic techniques? - RP6
- Disinfecting work surfaces
- Wearing gloves and goggles
- Having a lit bunsen burner
- Flaming culture bottlenecks to prevent contamination
- Use a sterile pipette
Give one reason why the student used aseptic techniques - RP6
The technique minimises the risk of bacteria from air contaminating the agar plate
The student incubated the agar plates at 25degrees. Suggest one reason why she didn’t incubate them at a higher temperature? - RP6
A higher temperature could be closer to the optimum temperature for bacteria that causes human disease. This would be dangerous for the student
Why do you transfer same volume of liquid of culture onto agar plate
Same number of bacteria to allow for comparison
Explain the purpose of boiling the agar
Avoid contimination of other bacteria
