RP 2 - Preparation of stained squashes of cells from plant root tips. Set-up and use of an optical microscope and preparation of a temporary mount

Question 1

Describe how temporary mounts of plant tissue are made

Answer 1

1.Thin slice/section;
2.Put on slide in water / solution / stain;
3.Add cover slip;
Accept: ‘between two slides’

Question 2

Describe how the scientist could have used the temporary mounts of leaves to determine the mean number of chloroplasts in mesophyll cells of a leaf

Answer 2

1. Select large number of cells / select cells at random;
   2.Count number of chloroplasts;
   3.Divide number of chloroplasts by number of cells

Question 3

The student cut thin sections of tissue to view with an optical microscope. Explain why it was important that the sections were thin.

Answer 3

1. To allow (more) light through;
2. A single / few layer(s) ofcellsto be viewed.

Question 4

When the student was making their microscope slides, they were told to ensure they did not move the coverslip sideways. Explain why.

Answer 4

To prevent cells from rolling on top of each other / to not damage the chromosomes

Question 5

Mitosis is important in the life of an organism. Give two reasons why.

Answer 5

To grow
To replace worn out / dead cells
To repair damaged tissue

Question 6

Explain why the biologist chose to examine 200 cells.

Answer 6

A representative sample that would give significant results.

Question 7

What was the purpose of heating the acid at stage 2 of your method? Name an alternative to heating

Answer 7

Increase KE to make it more reactive
OR
To break down cell wall

Alternative - use a stronger acid