CORE PRACTICAL: 1: preparing light microscope slides

Question 1

method for animal cells: human cheek cells

Answer 1

1- put a small drop of water on the microscope slide
2- gently swab the inside of your mouth with a cotton bud
3- gently rub the cotton bud in the drop of water
4- put a drop (or drops) of the stain (methylene blue) over the specimen
5- place the cover slip over the specimen

Question 2

method for plant cells: onion epidermal cells

Answer 2

1- peel some onion skin from inside one of the leaves in an onion bulb
2-use forceps to transfer onion skin onto slide. ensure that onion skin is flat, and that there are no trapped air bubbles
3-stain cell with iodine
4-place cover slip over

Question 3

what is the purpose of a cover slip?

Answer 3

-prevents the slide from drying out when it’s being examined.

Question 4

why is iodine used to stain plant cells?

Answer 4

-to make the internal structures (such as organelles) more visible.

Question 5

why and what are stains used for?

Answer 5

-most cells are colourless and so stains are used to add contrast.

Question 6

how can cell size be measured?

Answer 6

using an eyepiece graticule

Question 7

what is a graticule

Answer 7

glass piece with scale fitted into eyepiece lens

Question 8

what is a possible risk that is proposed by the microscope illumination? why? and how could this be prevented? (3)

Answer 8

Care must be taken when looking down the microscope

• ensure illumination is not too bright
• eye damage could be caused.

Question 9

what is a possible risk that is proposed by the microscope stains?

Answer 9

Care must be taken when using microscope stains as some are harmful

Question 10

what is a possible risk that is proposed by the coverslips and microscope slides? why?

Answer 10

Care when handling coverslips and microscope slides

-as broken glass could cut skin