Microscopes And Slides

Question 1

Making slides (5)

Answer 1

• Forceps are used to peel the thin, transparent layer of epidermis cells from the inside of a small section of onion leaf
• a few drops of Iodine solution or methylene blue are placed in the middle of slide
• Single Layer of epidermis cells are then placed on the microscope slide
• a clean coverslip is lowered onto the onion epidermis using a mounted needle or forceps (one end first as thus helps to prevent trapping air bubbles)
• View epidermis cells under microscope

Question 2

Why is Iodine or methylene blue used

Answer 2

These chemical stains colour the cells, making certain parts more obvious

Question 3

What is the purpose of the light source ?

Answer 3

Provides light which passes through the specimen and into the lens forming an image

Question 4

Why is it important to use a lower power objective lens

Answer 4

The field of view is wider and allows you to see more of the cells on the slide. This makes it easier to focus a sharp image

Question 5

Why is care need while rotating a high power lens into position above the slide ?

Answer 5

The end of the high power lenses are very close to the slide and can be damage while focusing

Question 6

Relationship of magnification equation

Answer 6

I
———
A x M

Question 7

Method of recording structures of a cheek cell (4)

Answer 7

• Rub a clean cotton bud gently over the inside of your cheek
• Smear The end of the cotton wool bud on the surface of a clean microscope slide
• Add one drop of methylene blue stain to the smear and slowly lower a cover slip on top of the methylene blue
• Observe cells on slide using low power objective lens

Question 8

How is accuracy increased ? (2)

Answer 8

• Use a ruler with smaller measurements to increase accuracy
• Use an electron microscope

Question 9

How has greater resolution of electron microscopes increased our understanding of cell structures?

Answer 9

Electron microscopes use a beam of electrons to allow us to see structures that can be as close as a 10000th of a micrometer and in much greater resolution, meaning we can see more detail of a structure and better understand how it might function

Question 10

Conversion of units from 1 micrometer to metre and millimetre

Answer 10

1 m - 1um x 1,000,000
1 mm - 1000 um
1 cm - 10,000um

Question 11

Why is it important to use the fine focus knob only when viewing an image at high power ?

Answer 11

Using other knobs focuses the image in and out too quickly and it’s difficult to adjust with precision

Question 12

Why should only 1 cell thick of epidermis be used

Answer 12

Onion tissue more than 1 cell would result in cells overlapping