Required practical 1 - Microscopy

Question 1

Describe how you would prepare a microscope slide using onion tissue

Answer 1

• Peel off epidermal layer using forceps.
• Place sample on drop of water on microscope slide.
• Add drops of iodine to solution.
• Lower cover slip onto sample using mounting needle.

Question 2

Why is a thin sample of tissue required?

Answer 2

Allows light to pass through so internal structures can be observed.

Question 3

Why is water added to the slide before the sample is mounted?

Answer 3

Allows the sample to be suspended between the slide and cover slip, ensuring the cover slip stays in place.

Question 4

Why is iodine solution added to stain the cells?

Answer 4

Iodine solution adds contrast - reacts with starch in plant cells and turns blue-black. This allows internal structures such as nucleus to be more visible.

Question 5

Why is the cover slip lowered using a mounting needle?

Answer 5

Ensures no air bubbles are trapped.

Question 6

How could you measure the length of a cell viewed under the microscope?

Answer 6

Measure using eyepiece graticule and calibrate with stage micrometer.

Question 7

How would you calculate the magnification of an image?

Answer 7

Magnification = observed cell length / actual cell length

Question 8

What safety precaution should be taken during the experiment?

Answer 8

Wear safety goggles when handling iodine solution.