Biology Paper 1 Flashcards
Biology paper 1 practicals
Describe how to use a light microscope
- Put a droplet of water on a slide
- Place a tissue sample on the slide
- Add a few drops of stain to be able to see the sample
- Add the cover slide
- Focus on cells using low power
- Change to high power and refocus
- Draw a diagram of the cell you can see and label
- Add a scale line
Describe an investigation to find the effect of different concentrations of sugar solution on plant tissues
- Cut some cylinders of potato tissue and measure their mass
- Place cylinders in different concentrations of sugar solution
- After about 30 mins measure the mass again making sure potato is dry
Describe the test for sugars
Add benedicts reagent and heat in a water bath for 2 mins. Solution will turn red if sugar is present
Describe the test for starch
Add iodine solution, if starch is present it will turn blue-black
Describe the test for protein
Add biuret reagent, if protein is present it will turn purple
Describe an investigation to find the effect of pH on the rate of reaction of an enzyme
- Put a test tube containing starch solution and a test tube containing amylase in to a water bath at 37°C.
- After 5 mins add amylase solution to the starch.
- Every 30 secs take a drop from the mixture and test it for starch using iodine solution.
- Record how long it takes for starch to be completely digested.
- Repeat experiment with different pH values using different buffer solutions
Describe an investigation about the effect of antibiotics on bacterial growth
- Sterilise an inoculating loop in a flame and inoculate a petri dish with a culture of bacteria
- Soak small discs of filter paper in different antibiotics.
- Using sterilised forceps, place the antibiotic discs on the surface of the agar.
- Incubate the dish upside down to avoid condensation at 25°C to avoid the growth of harmful bacteria.
Describe an investigation about the effect of light on photosynthesis
- Place a piece of pondweed in a beaker of water and shine a light at it using a lamp a measured distance away.
- Record the number of bubbles of gas given out of the pondweed in a minute.
- Repear this with the lamp at different distances.
- Record readings and draw a graph to show the inverse square law of light
What are the variables of the investigation in to sugar solution on plant tissues
Independent- the concentration of sugar solution
Dependent- the change in mass of the potato
Control- temperature, length of time, volume of solution
Possible mistakes of the investigation of concentrations of sugar solution on plant tissue?
Cylinders need to be left in solution long enough for a significant change in mass.
Potato must be dried so there isnt excess water on potato.
Possible mistakes of the investigation of concentrations of sugar solution on plant tissue?
Cylinders need to be left in solution long enough for a significant change in mass.
Potato must be dried so there isnt excess water on potato.
Variables of the investigation of pH on amylase enzymes
Independent- the pH
Dependent- the time taken for starch to be digested
Control- temperature, concentration, volume of starch and amylase
Variables of investigation about effect of antibiotics on bacterial growth
Independent- type of antibiotic.
Dependent- area around each disc clear of bacteria.
Control- concentration of antibiotic used, length of time discs are soaked.
Variables in the investigation of light on photosynthesis
Independent- light intensity (distance of light)
Dependent- number of bubbles per minute
Control- piece of pondweed, temperature, concentration of CO2
Precautions of the agar plate to keep it sterilised?
Use sterilsed inoculator by using a flame. Use sterilised forceps. Open and close the lid very quickly when putting stuff on agar to avoid contamination of microorganisms from the air. Store upside down to avoid condensation dripping on it. Store at 25°C to avoid growth of harmful bacteria.
