Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
43 Cards in this Set
- Front
- Back
|
What is the first required practical? |
How temperature affects the rate of milk hydrolysis |
|
|
What was the independent variable?1 |
Temperature |
|
|
What was the dependent variable?1 |
Time taken for the reaction to occur. From this, we worked out the rate |
|
|
What control variables were there?1 |
Enzyme concentration and volume, pH, volume of milk, concentration of milk |
|
|
What are precautions? |
Measures taken to ensure our experiment and results are valid |
|
|
What precautions did we take?1 |
We allowed the substrate and enzyme to stand in the water baths of their temperature for 5 minutes to equilibrate. |
|
|
What were the limitations?1 |
It was hard to visually assess when the cross disappeared. |
|
|
How did we minimise the effect of this?1 |
We used the same person to make the judgement |
|
|
What was the control for this experiment? |
Equal volume of boiled enzymes. No colour change should occur |
|
|
Give a brief overview of the method.1 |
We put a cross on the bottom of a beaker containing the milk and added the enzymes along with a buffer at different temperatures. We recorded how long it took for the cross to become visible |
|
|
What was required practical 2? |
Preparing a root tip squash for microscopy |
|
|
What is a brief overview of this required practical? |
We took a root and cut off the tip. We then put it on a watch glass with acetic orcein stain and HCl, the warmed it. We then put it on a glass slide, added more stain and a drop of water and covered with a cover slip. We used a dissecting needle to tap the tip and wrapped filter paper around the slide and pressed down. |
|
|
Why did we add heat and HCl? |
To loosen the middle lamellae that hold the cell together |
|
|
Why do we squash the sample down? |
So it's thin enough to be seen under a light microscope, allows light to pass through. |
|
|
Why do we use a stain? |
To provide contrast |
|
|
What is the equation for mitotic index? |
Cells in mitosis/ total cells |
|
|
How do we work out the time taken for a stage? |
(Number of cells in the stage/total number of cells) x length of one cell cycle |
|
|
What was the third required practical? |
Making a serial dilution to identify the water potential of potato tissue. |
|
|
What is a brief overview of this practical? |
Make up 5 different concentrations of sucrose. Cut potato chips into equal lengths using a ruler and scalpel. Dry with paper towels and weigh each. Place into sucrose solution with a bung and leave. Remove, pat dry and reweigh. Calculate change in mass and draw a graph. |
|
|
How can we use this to find the potato's water potential? |
It is the point on the graph where there's no change in mass |
|
|
What was the independent variable? |
Solution concentration |
|
|
What was the dependent variable? |
Change in mass |
|
|
What were our control variables? |
Temperature, surface area, type of potato |
|
|
Why do we dry the potatoes? |
To remove excess solution and control the independent variable |
|
|
How do we make a serial dilution from a 2M solution with a scale factor of 2? |
Add 10cm3 of 2M solution to the first test tube and fill the others with 5cm3 of water. Draw 5cm3 from the first into the second with a pipette and mix. Repeat. |
|
|
How could we improve our accuracy? |
We could use more concentrations at smaller intervals |
|
|
What was required practical 4? |
Investigating cell membrane permeability of beetroot |
|
|
What is a general overview of our method for cell membrane permeability? |
We placed water and a buffer into test tubes in water baths of set temperatures.We then cut beetroot chips of the same length, washed them and dried them.We then added them to the test tube. Then we shook the tube and removed the cylinders. We set the colorimeter to the green filter and zeroed it with water. We then measured absorbance. |
|
|
What was out independent variable? |
Temperature |
|
|
What was our dependent variable? |
Absorbance |
|
|
What do the results show? |
The 3 stages of cell membrane permeability. |
|
|
How do you label diagrams? |
With ruler-drawn lines with no arrow heads |
|
|
What must we not do when drawing a diagram? |
Shade in |
|
|
What was practical 6? |
Using aseptic techniques to investigate the effect of antimicrobial substances on microbial growth. |
|
|
What was our independent variable? |
Type of antibiotic |
|
|
What was our dependent variable? |
Clear zone area |
|
|
What is the formula to work out the clear zone area? |
Pi r squared |
|
|
What were our control variables? |
Type of bacterium, incubation time, concentration of the antibiotic, temperature f incubation, size of discs |
|
|
What was a limitation? |
The rate at which the substance diffuses through agar |
|
|
Why do we flame the neck of the glass bottle after opening? |
This causes air to move out, preventing contamination of the bacteria etc. |
|
|
Why do we invert the plate to incubate? |
To reduce the chance of condensation droplets falling onto the surface of the plate and dispersing the bacteria |
|
|
Why do we seal the lid with tape but not all around? |
To prevent bacteria from escaping but allow O2 in as the bacteria respire aerobically. Also, some pathogens respire anaerobially and we want to prevent their growth. |
|
|
Why do we incubate at 25 degrees c? |
We want a good rate of growth but above this, it will favour the growth of potential human pathogens |
