Required Practicals Paper 1

Question 1

Describe how to use an optical microscope to look at cells on a microscope slides

Answer 1

Place the slide onto the stage and use the clips to hold the slide in place 
Select the lowest power of objective lens (Usually 4 x)
Slowly turn the course focusing dial to position the object lens so it almost touches the microscope slide
Always look from the side because if we looked through the eyepiece wild positioning the objective lens, and there’s a risk that we can damage the slide
When it almost touches the side we stopped turning the dial
After we looked down through the eye peace then Slowly turn the course focusing dial
Increasing the distance we do this until the cells come into focus
After we use define focusing dial to bring the cells into a clear focus

Question 2

Describe how to investigate the effects of osmosis on plants tissues using potatoes, beetroot or parsnip

Answer 2

First you use a cork borer to produce three cylinders of potato (Using this makes all of the cylinders the same diameter)

use a scalpel to trim the cylinders to the same length (around 3cm)

Measure the length of each cylinder using a ruler and a mass of each cylinder using a balance

Place each cylinder into a test tube

Add 10 cm³ of a 0.5 molar sugar solution into the first test tube

To the second test tube add 10 cm³ of 0.25 molar sugar solution

Then add 10 cm³ of distilled water to the third test tube (Distilled water contains no dissolved substances)

Then leave the cylinders with the substance in it overnight to allow osmosis to take place

After that remove the potato cylinders and gently roll them on the paper towel to remove any surface moisture.

Finally measure the length and the mass of the cylinders again

Question 3

How can you investigate the effect of pH on enzyme activity

Answer 3

Put a drop of iodine solution into every well of spotting tile.

Place a Bunsen burner on a heatproof mat and a tripod and gauze over the Bunsen burner.

Put a bigger on top of the water of the tripod I need the water until it is 35°C (Use a thermometer to measure the temperature)

Use a syringe and add 1 cm³ of amylase solution and 1 cm³ of butter solution with a pH of 5 to a boiling tube.

Using a test tube put the tube into a beaker of water for 5 minutes

Next use a different syringe to add 5 cm³ of starch solution into the boiling tube.

mix the contents of the boiling tube and start a stop clock

Records how long it takes for amylase to break down all the starch

Use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and drop it in the well of the spotting tile.

When the iodine solution remains Brownie Orange starch is no longer present

Then repeat the whole experiment with a buffer solutions on a different pH values to see how it affects the time.