Practicals

Question 1

Microscopy

Answer 1

Peel off epidermal layer of onion using forceps
Mount onto microscope slide with drop of water making sure the tissue lies flat
Add 2 drops of iodine to stain the cells
Place cover slip at angle to ensure no bubbles are present
Rotate the objective lens so that low power lens is in line with stage
Turn the cource focus stage so that the stage is as close to the objective lens as possible
Place microscope slide in the centre of the stage
Focus slide
Record an image then rotate the objectives so that the high power objective is inline with the stage

Question 2

Osmosis practical

Answer 2

Use cork border to cut 5 potato cylinders
Trim ends of cylinders using sharp knives
Measure and record the length and mass of each cylinder
Measure different quantities of the sugar solutions and add to the boiling tubes making sure to label them
Add potato cylinder to each tube
Leave in cylinders overnight, in a test tube rack
Remove cylinders and lightly pat dry
Measure the length and mass of each cylinder and calculate the percentage change

Question 3

Amylase practical

Answer 3

Place drop of iodine solution in each well of spotting tile
Take 3 test tubes in 1 but amylase and in other 1 put starch and in final one put 5ph buffer solution (make sure all same volume)
Place all 3 tubes in water bath at 30 degrees,leave for 10 mins to allow all solutions to be same temp
Add all 3 test tubes into 1 mix with stiring rod ,return to waterbath and start a stopwatch
After 30 secs use stiring rod to transfer 1 drop of the solution to well in spotting tile which contains iodine
The sample should turn black
Take sample for every 30 secs until iodine remains orange
When the iodine remains orange it tells us that starch is no longer present
Record the time
Repeat this experiment with differnt ph buffers

Question 4

What are the problems with the amylase practical

Answer 4

only taking samples every 30 seconds. we only have an approximate time for the reaction to completely finish address this by taking samples every 10 seconds.

Question 5

Food test practical + results

Answer 5

Take good sample grind it with distilled water using mortar and pestal
Add paste into beaker and add more distilled water ,stir the solution
Filter soltuion to remove suspended food particles

Sugar -Benedict’s-blue to red(additional heat solution
Starch-iodine-orange to black
Protein-buiret-blue to lilac
Lipids-ethanol-cloudy emultion(additional,don’t filter solution

Question 6

Photosynthesis practical

Answer 6

Place a test tube rack containing a boiling tube 10 cm away from the light source using the ruler.
2. Fill the boiling tube with a fixed volume of sodium hydrogen carbonate solution.
3. Place the cut pondweed into the boiling tube with the cut end at the top. Gently push the pondweed down with the glass rod.
4. Leave the boiling tube to rest for 5 minutes.
5. Start the stopwatch and count the number of bubbles produced in one minute.
take a mean.
Record in a table
8Repeat steps 1-7 for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source.
9. Plot a graph of the rate of photosynthesis against light intensity